The landscape evaluation of Hebe at the North Willamette Research and Extension Center (NWREC) was established in 2000 and was removed in 2009. The purpose of the planting was to compare performance of a range of Hebe species and cultivars under typical western Oregon conditions and gather information on their landscape performance. One of the main goals of this trial was to develop comparative data on hardiness of Hebe cultivars and species and identify cultivars that were capable of tolerating typical cold events in a Pacific Northwest winter. In addition to assessing hardiness, other goals were to record flowering and growth information on the various cultivars and species, and also any pest or disease problems.

  • Data Collection
  • Cold Hardiness of Hebe Cultivars and Species 
  • Cold Hardiness Results 
  • Pests and Diseases
  • Drought Tolerance 
  • Books and Websites
 

The first 48 selections of Hebe were planted in 2000. Over the following 4 years, plants were received from cooperators, usually as unrooted cuttings. These were rooted, grown on to 4” or 1 gallon-sized plants, and added to the evaluation each April. In 2001, 88 selections were added to the planting, and in 2002, an additional 45 were added. In 2003, 80 were added, and a final 33 selections were planted in 2004. Primarily because of plant losses to cold and to some extent disease, the evaluation consisted of 201 clones in November, 2006.

 

The planting consisted of a 0.4-acre plot, with 16 double rows, with individual plants spaced at 3’ by 3’ within each double row. Three plants of each clone were planted to allow statistical evaluation of data, although because of the sequential planting over several years, the plants are not randomly distributed in the evaluation, but planted in groups of three. Planting occurred once per year, in April or May, to allow for good plant establishment before winter. Following planting, each row was mulched with bark dust.

 

Each established plant was fertilized with 2 tbs of 13-13-13, while each new plant received ½ tbs of the same fertilizer. A 5’ wide grass strip separated each row for access. A micro sprinkler irrigation system was installed with the assistance of a grant from the Hardy Plant Society of Oregon.

Meteorological data, including daily maximum and minimum temperature, rainfall and wind speed, are available from the US Bureau of Reclamation Agrimet weather station installed in 1998, located immediately adjacent to the plot.

Plants came from a variety of sources in the western United States and Canada, including nurseries in Oregon, the University of California (Santa Cruz) Arboretum, Strybing Arboretum in San Francisco, Washington Park Arboretum in Seattle and the University of British Columbia Botanical Garden in Vancouver, B.C. However, the majority of the collection was provided by cooperators the New Zealand and the United Kingdom, including Lincoln Botanical, Landcare Research and Christchurch Botanic Garden (New Zealand) and individuals within The Hebe Society (U.K.).

Data Collection

Plant size was recorded at planting time and again in October at the end of the growing season. Plant size was recorded by measuring the height, and two width measurements at right angles to one another, allowing a plant size index to be calculated.

 

Data on flowering was collected once per month throughout the year, as flowering on various selections continues almost year-round. Flowering information included a rating of flowers on a 0-5 scale. Cold hardiness information was collected following cold events and again in early April. Plants were rated for damage on a 0-5 scale, with 0 indicating no damage and 5 indicating plant death. Intermediate ratings indicate varying levels of damage to leaves and shoot dieback. Information on insect pests and disease problems was collected on a casual basis. The main disease problems proved to be Phytophthora root rot; leaf spot, caused by Septoria exotica, and downy mildew, caused by Peronospora grisea. See Pests and Diseases for more information. A more recent evaluation involves assessing foliage quality and form of the plants, again on a 0-5 scale. The goal was to give some indication of the appearance of the plant in general.

Cold hardiness of Hebe cultivars and species

In New Zealand, Hebe species can be found growing in a wide range of habitats, from sea level to alpine regions, so it is no surprise that cold hardiness of the species, and the cultivars derived from them, varies widely as well. There is truth to the old saying that hardiness of Hebe is related to leaf size. As one goes up in elevation from sea level to alpine areas in New Zealand, the leaf size of the Hebes tends to decrease, and overall plant size decreases as well (Kristensen, 1989). Other characteristics like coriaceous and/or glacous leaves and white flowers are also typical of alpine Hebe species (Wardle, 1978). So, generally speaking, you could say that the larger the leaf of the Hebe, the less cold hardy it tends to be. As with all living things, the rule is not perfect, but the most tender Hebes are usually the largest-leaved, and the hardiest are those with the smallest leaves.

The most extensive study of cold hardiness of Hebe was undertaken by Warrington and Southward (1995), who assessed summer and winter hardiness of 35 species and cultivars. This study showed that large differences in hardiness existed among the various selections. Not surprisingly, the hardiest of those tested were two whipcords, H. cupressoides and H. propinqua, both of which are typically found in alpine or subalpine regions and have very tiny leaves. More important than altitude however, this study observed significant differences in hardiness of species from northern or southern parts of New Zealand, with species of southern origin exhibiting greater overall hardiness.

Some of the research on hardiness of Hebe has utilized excised shoots as sample material for laboratory studies. Bannister (1986) found that detached shoots of Hebe albicans, a South Island species often found in subalpine scrub above 1000m, withstood mid-winter temperatures of -10°C, one of the hardier of the native species studied. Other Hebe species were not tested. In a more extensive study, Bannister (1990) found that mid-winter freezing resistance of foliage of H. buchananii, a diminutive shrub of alpine areas in Canterbury, was as low as -11°C. Freezing resistance of foliage of H. rakaiensis and H. salicifolia, both of which are found at lower elevations on the South Island, was found to be -5.2°C and -6°C respectively. Buds of H. rakaiensis were found to be hardy to -11°C, significantly hardier than leaves. Testing of both H. speciosa, a tender species from seacoast areas of the North Island, and H. odora, a widely distributed shrub of subalpine scrub, found early-winter hardiness of -6°C and -9°C, respectively. Sakai and Wardle (1978) tested excised stems of a wide variety of New Zealand trees and shrubs in mid-winter for hardiness. H. brachysiphon was rated as one of the hardiest species tested, having leaf and bud hardiness of -10°C and -13°C, respectively.

Probably the most extensive anecdotal evidence for hardiness of a wide range of Hebe species and cultivars is provided by Trees and Shrubs hardy in the British Isles (Bean and Clarke, 1991). This monumental work, in 5 volumes, lists descriptions and basic hardiness information on over 100 Hebe species and cultivars. The most extensive field trial of Hebes which included cold hardiness results was the trial of RHS Garden Wisley between 1980 and 1982. In addition to selecting 33 cultivars or species for awards, the trial also indicated which of the trialed plants failed to survive the winter of 1981. Harris and Decourtye (1995) evaluated cold hardiness of many New Zealand plants in field trials over several years in Angers, France. This trial indicated that H. dieffenbachii was tolerant of prolonged cold weather with temperatures as low as -12°C. H. pauciramosaH. pinguifolia and H. amplexicaulis showed some foliar damage from these conditions. Later data from this trial (Harris et al. 2000) showed that H. albicans and H. subalpina were not injured or suffered only slight injury from prolonged winter cold snaps with temperatures as low as -15°C.

In North America, Hebes are grown primarily as a landscape plant. Because of the intolerance of most Hebes for excessively hot or cold weather, cultivation of Hebes in North America is almost entirely limited to west of the Cascade or Sierra Nevada Mountains in California and the Pacific Northwest. Elsewhere in North America, the climate is generally too cold or hot, or both, to allow for outdoor cultivation, although dedicated enthusiasts have been successful with some varieties in many other areas.

Even in the Pacific Northwest, Hebes are sometimes thought of as too tender for general landscape use, a reputation which is primarily the result of experience with a few popular cultivars which are not particularly cold hardy. Plantings of ‘Amy’, ‘Tricolor’ or ‘Patty’s Purple’ have been severely damaged in cold events on a regular basis, which has unfortunately given the entire genus this reputation. The key to growing these tender cultivars is to provide a protected location near a house or nearby plant.

Despite this, many other commonly-available Hebe cultivars like ‘Emerald Gem’, H. carnosula, or H. cupressoides ‘Boughton Dome’, never suffer winter damage.

The level of injury to cold will of course vary depending on the temperature experienced. The hardiest Hebes-the whipcord types and other small-leaved plants-have not typically shown any reaction to winter temperatures in western Oregon over the course of this trial. Since 2000, the minimum temperatures have been no lower than 19°F (-7°C). Even tender Hebes will tolerate temperatures of 25°F without showing signs of stress, especially if these temperatures occur in mid-winter. Abnormally cold temperatures in the fall or early spring are often responsible for damage to these plants and that has been the case in this trial.

The mildest form of damage is leaf discoloration at the shoot tips. More severe cold damage will cause browning and leaf loss on shoot tips.

Major cold damage will cause browning of most of the leaves on the canopy, followed by dieback. Sometimes, plants will recover over a 2-3 year period from this damage if subsequent winters are mild. Very severe, sudden cold often turns the entire plant brown and sensitive cultivars do not recover from this damage and require replacement.

References

Bannister, P. 1986. Winter frost resistance of leaves of some plants growing in Dunedin, New Zealand, in winter 1985. New Zealand Journal of Botany. 24:505-507.

Bannister, P. 1990. Frost resistance of leaves of some plants growing in Dunedin, New Zealand, in winter 1987 and late autumn 1989. New Zealand Journal of Botany. 28:359-362.

Bean, W.J. and D.L. Clarke. 1991. Trees and shrubs hardy in the British Isles. 5 Volumes. John Murray.

Harris, W., A. Cadic and L. DeCourtye. 2000. The acclimatization and selection of New Zealand plants for ornamental use in Europe. Proceedings of the 19th International Symposium on Improvement of Ornamental Plants. Acta Horticulturae 508:191-196.

Harris, W. and L. Decourtye. 1995. Observations on cold damage to New Zealand plants grown at Angers, France. Horticulture in New Zealand. 6(1):9-19.

Kristensen, L. 1989. The Genus Hebe-A botanical report. Danish research Service for Plant and Soil Science. Report #S-2034.

Sakai, A. and P. Wardle. 1978. Freezing resistance of New Zealand trees and shrubs. New Zealand Journal of Ecology. 1:51-61.

Wardle, P. 1978. Origin of the New Zealand mountain flora, with special reference to trans-Tasman relationships. New Zealand Journal of Botany. 16:535-550.

Warrington, L.J. and R.C. Southward. 1995. Seasonal frost tolerance of Hebe species and cultivars. New Zealand Journal of Crop and Horticultural Science. 23:437-445.

Cold Hardiness results

Winter temperatures over the course of the trial varied significantly, as might be expected. Temperature data for each period from late October through mid-March, from 2000-2006, are shown in the graphs below. Generally speaking, only temperatures of 27°F or below are of significance, as in this trial, even the most tender Hebe seemed not to suffer injury above this temperature, regardless of when it occurred. More than the actual minimum temperature, the date on which a low temperature was recorded has had the most profound impact on Hebe survival and damage at this site.

The most serious cold damage which occurred during the evaluation followed cold temperatures in early November, 2002, when temperatures dropped suddenly to 22°F. This was a particularly early freeze that caught many Hebes growing and in full bloom, and did extensive damage to many selections, some of which failed to recover. A similar, though less severe freeze, occurred on November 1, 2003, when the temperature again dropped quickly from mild lows to 24.6°F. Again, because of the relatively severe temperature early in the winter, significant damage was done to a wide range of plants. Another early freeze occurred in the first winter of the trial, when the temperature dropped to 23°F on November 18th. The fourth severe freezing event occurred in mid-February, 2006, when the temperature dropped to 20°F on February 20. Much like the early November freezes, this was an uncharacteristically low temperature for the time of year, and occurred following a period of relatively mild temperatures. By late February, many plants, including Hebes, are beginning to grow, and are more susceptible to cold injury. These four events accounted for virtually all of the observable damage to Hebes over the duration of this trial.

In contrast to the injury caused by these early, or late, freezes, similar temperatures in mid-winter have caused no identifiable damage. Temperatures in the low 20’s°F have occurred in January 2004 (20°F, January 6), January 2005 (23°F, January 5) and December 2005 (19.5°F, December 16). In two of the winters of this evaluation (2001-02 and 2004-05), winter temperatures were so mild that no damage which could be attributed to cold weather could be observed.

The accompanying chart shows cold damage to Hebes in the trial by year.

    Cold damage rating by year
RowPosPlanted Plant Name00-0101-0202-0303-0404-0505-06AVG
1A12000Hebe 'Wardiensis'0.0.0.00.0.0.00.0
1A42000Wiri Image'0.0.3.04.3.0.01.8
1A72000Nicola's Blush'0.3.3.32.3.0.01.5
1A102000Mrs. Winder'0.0.2.00.0.0.00.5
1A132000H. recurva0.0.1.00.0.0.00.3
1A162000Margret'0.0.0.0...0.0
1A192000Purple Picture'0.0.4.05.0..3.0
1B12000Icing Sugar'0.0.2.30.0.2.01.1
1B42000McKean'0.0.0.00.0.0.00.0
1B72000H. salicifolia0.0.2.00.0.0.00.5
1B102000Autumn Glory'0.0.3.30.0.0.00.8
1B132000H. sp. (bidwillii)='Pattys Purple'4.0.4.3...4.2
1B162000H. sp ('Little')2.0.4.0...3.0
1B192000H. canterburiensis2.0.4.3...3.2
2A12000H. sp ('Powis Castle Blue')='Blue Mist'0.0.....0.0
2A42000Alicia Amherst'1.3.4.33.5..3.0
2A72000H. anomala 'Purpurea'0.0.0.00.0.1.30.3
2A102000Amy'1.6.4.04.3..3.3
2A132000H. topiaria0.0.0.00.0.0.00.0
2A162000Patty's Purple'2.0.4.35.0..3.8
2A192000H. sp (buxifolia)0.0.0.0...0.0
2B12000H. sp (NWREC 528)0.0.0.00.0.1.00.3
2B42000Alameda'0.0.1.02.0.0.00.8
2B72000H. carnosula0.0.0.00.0.0.00.0
2B102000Oswego'0.0.0.60.0.0.00.2
2B132000H. cupressoides 'Boughton Dome'0.0.0.00.0.0.00.0
2B162000H. 'Silver Queen'3.6.5.0...4.3
2B192000H. speciosa1.6.4.3...3.0
3A12000Heliohebe 'Hagley Park'0.0.2.60.0.0.00.7
3A42000H. sp ('Prince')3.0.5.05.0..4.3
3A72000H. sp. (haastii)0.0.0.00.0..0.0
3A102000Great Orme'2.0.4.65.0.3.03.7
3A132000H. pinguifolia 'Pagei'0.0.2.00.0.0.00.5
3A162000Emerald Gem'0.0.0.00.0.0.00.0
3A192000Youngii'0.0.0.00.0.0.00.0
3A222000Wiri Charm'0.0.3.62.0.4.02.4
3A252000H. speciosa 'Tricolor'5.0.....5.0
3A282000H. sp. ('Cottage Red Edge')2.0.....2.0
3A312001H. elliptica..5.0 ..5.0
3B12000Paula'1.0.5.0...3.0
3B42000Jane Holden'1.0.4.02.5.1.02.1
3B72000Caledonia'0.0.3.01.6.0.01.2
3B102000H. 'Silver Queen'2.6.4.6...3.6
3B132000Autumn Glory'0.0.4.01.0.0.01.3
3B162000H. traversii0.0.4.02.3.3.32.4
3B192000Heliohebe hulkeana0.0.3.53.0..2.2
3B222000Parahebe olsenii2.0.4.0...3.0
3B252000H. speciosa 'Variegata'2.3.5.0...3.7
3B282000Purple Queen'3.0.....3.0
3B312001H. x andersonii 'Andersonii Variegata' .5.0...5.0
4A12001Sarana' .3.02.0.1.02.0
4A42001Wiri Cloud' .2.00.0.3.01.7
4A72001H. anomala .0.00.0.0.00.0
4A102001La Seduisante' 83.113 .5.0...5.0
4A132001H. speciosa 91.612 .4.03.0.2.03.0
4A162001H. corriganii 91.663 .1.31.0.1.01.1
4B12001H. odora 'New Zealand Gold' .0.00.0.0.00.0
4B42001H. strictissima .2.00.0.0.60.9
4B72001H. pubescens .4.5...4.5
4B102001Denise' .2.32.0.0.01.4
4B132001Parahebe 'Snowcap' 94.96 .2.03.6..2.8
4B162001Janet' .4.04.0.0.52.8
5A12001H. stricta var. macroura .4.03.5.1.02.8
5A42001Cressit' .4.5...4.5
5A72001H. sp. (Strybing H-2) .0.00.0.0.00.0
5A102001Bracken Hill' .0.62.0.0.00.9
5A132001Sapphire' .2.00.6.0.00.9
5A162001H. albicans 'Snow Cover' .1.01.3.0.00.8
5A192001Sarnia' .3.60.3.0.01.3
5A222001Purple Tips' 89.54 .5.0...5.0
5A252001H. albicans (prostrate form) .2.02.0.0.01.3
5A282001H. obtusata .4.05.0..4.5
5A312001H. sp (Strybing H-12)='Autumn Glory' .4.02.0.0.02.0
5B12001H. sp (Strybing H-8)='Andersonii Variegata' .5.0...5.0
5B42001H. macrocarpa var. brevifolia .5.0...5.0
5B72001Lindsay White' .4.03.0.0.62.5
5B102001Pink Pearl' .5.0...5.0
5B132001White Gem' .3.02.0.0.01.7
5B162001Champagne' .3.02.0.2.02.3
5B192001Andersonii Variegata' 83.118 .5.0...5.0
5B222001Hinerua' .0.00.0.0.00.0
5B252001H. traversii 89.5 .5.0...5.0
5B282001H. stricta var. lata .3.02.0.0.01.7
5B312001H. sp. (Strybing H-1) .5.0...5.0
6A12001Josephine' .2.00.0.0.00.7
6A42001H. macrocarpa v. brevifolia 84.78 ..0.0.0.00.0
6A72001H. sp. (Strybing H-14) .1.00.0.0.00.3
6A102001H. albicans 'Sussex Carpet' .2.01.3.0.01.1
6A132001Eveline' .3.02.0.0.01.7
6A162001H. sp. (Strybing H-16)=H. rigidula .2.01.3.0.01.1
6A192001H. diosmifolia (Strybing H-15) .3.00.0.0.31.1
6A222001H. sp (Strybing H-10) .5.0...5.0
6A252001H. sp. (Strybing H-9) .4.63.0.2.03.2
6A282001H. salicifolia v. angustissima .3.03.3.1.62.6
6A312001Diana' .5.0...5.0
6B12001H. parviflora var. angustifolia .2.61.3.2.02.0
6B42001Pink Payne' 88.102 .4.6...4.6
6B72001Beatrice' .3.02.3.1.02.1
6B102001H. vernicosa .3.04.6.1.02.9
6B132001H. macrantha 91.631 .0.00.0.0.00.0
6B162001H. amplexicaulis .2.3 .0.01.2
6B192001Blue Gem' .5.0...5.0
6B222001Lavender Spray' .3.33.0.2.02.8
6B252001Loganioides' .2.50.0.0.00.8
6B282001H. elliptica 'Variegata' (Strybing H-13) .5.0...5.0
6B312001H. diosmifolia 84.75 .5.0...5.0
7A12001H. sp. (Western Hills) .0.30.0.0.00.1
7A42001Wiri Gem' 94.56 .5.0...5.0
7A72001H. sp. (elliptica x crassifolia) ..0.0.0.00.0
7A102001Glauca' 89.221 .0.00.0.0.00.0
7A132001H. sp. (Strybing H-3) .0.00.0.0.00.0
7A162001Mohawk' (=Purple Pixie) .4.02.3.0.02.1
7A192001La Favorite' .0.03.0.0.01.0
7A222001H. sp. (Strybing H-4) .5.0...5.0
7A252001H. x lewisii 'Lewisii' .5.0...5.0
7A282001Inverey' .0.00.6.0.00.2
7A312001Pink Fantasy' .3.32.0.2.02.4
7B12001H. macrocarpa var. latisepala .5.0...5.0
7B42001Inverey' 89.18 .1.00.6.0.00.5
7B72001H. rigidula .0.00.0.0.30.1
7B102001Violet Snow' .3.02.5.0.01.8
7B132001Co-ed' .4.6...4.6
7B162001H. elliptica .4.6...4.6
7B192001Oratia Beauty' .2.02.3.0.01.4
7B222001Pewter Dome' .1.32.0.0.01.1
7B252001Hartii' 94.51 .1.0..5.03.0
7B282001H. sp. (Strybing H-5) .4.0...4.0
7B312001H. 'Violaceae' .4.6...4.6
8A12001H. brachysiphon 89.218 .5.00.0.0.01.7
8A42001H. macrocarpa var. macrocarpa .0.0...0.0
8A72001Blue Mist' .3.02.0.0.01.7
8A102001H. pimelioides 'Quicksilver' .0.30.0.0.00.1
8A132001H. albicans 242/99 .1.01.5.0.00.8
8A182001H. pinguifolia .0.00.0.0.00.0
8A202001Blue Elf' .4.03.0.3.03.3
8A232001Maori Gem' .0.00.0.0.00.0
8A262001Pascal' .1.02.0.1.01.3
8A292001Wiri Gem' .5.0...5.0
8A322001Wiri Vision' .5.0...5.0
8B12001H. speciosa 'Pink' .5.0...5.0
8B42001H. hectorii var. laingii 94.53 .0.00.0.0.00.0
8B72001Violet Snow' .5.0...5.0
8B102001H. sp. (Halifax Hardy) .0.00.0.0.00.0
8B132001H. subalpina 331-98 .0.41.0.0.00.5
8B202001H. 'Tricolor' .5.0...5.0
8B232001Blue Gem' .3.64.0.0.62.7
8B262001Blue Clouds' .3.02.3.0.01.8
8B292001Wiri Mist' .1.62.0.0.01.2
8B322001(do not record, mix of clones) ..0.0 0.00.0
9A12001H. macrocarpa 'Pink' .5.0...5.0
9A42001Squalida' .2.53.0.0.01.8
9A72001H. sp. (diosmifolia x albicans) .2.33.0.0.01.8
9A102001H. rupicola .0.30.0.0.00.1
9A132001Leonard Cockayne' .0.00.0.0.00.0
9A162001Bowles's Hybrid' .4.02.0.0.02.0
9A192002H. 'Affinis' 89.60 .5.0...5.0
9A222002Pink Paradise (PVR) .1.02.0.2.01.7
9A252002H. sp. 84.86 .5.0...5.0
9A282002H. gibbsii 89.44 .0.00.0.0.00.0
9A312002H. sp. (odora varprostrata) .0.00.0.0.00.0
9B12001Primley Gem' .5.0...5.0
9B42001H. albicans 83.120 .1.01.3.0.00.8
9B72001H. corriganii .4.04.0..4.0
9B102001H. carnosula 'Mount Stewart' .0.00.0.0.00.0
9B132001H. gracillima .3.32.5.1.02.3
9B162002MacEwanii' 83.380 .1.02.0.0.01.0
9B192002H. sp. (Strybing H-17) .3.03.5.0.02.2
9B222002H. sp. (venustula) .1.03.6.0.01.5
9B252002Wingletye' .0.00.0.0.00.0
9B282002Wiri Spears' 94.61 .4.3...4.3
9B312002H. townsonii 91.747 .4.6...4.6
10A12002Parahebe formosa 90.178 .2.03.0.4.03.0
10A42002H. albicans 83.120 .0.60.0.0.00.2
10A72002H. divaricata 84.76 .3.00.0.0.01.0
10A102002H. venustula 'Sky Blue' .0.30.0.0.00.1
10A132002H. cupressoides 'Nana' 89.23 .0.00.0.0.00.0
10A162002H. sp. ('Patty's Purple Variegated') .5.0...5.0
10A192002H. ochracea 'James Stirling' .0.00.0.0.00.0
10A222002Clear Skies' PVR .1.00.0..0.5
10A252003Parahebe 'Snowcap' ..3.0.2.02.5
10A282003Mary Antoinette' ..2.0.2.62.3
10B12002H. pauciramosa var. masonae .0.00.0.0.00.0
10B42002Wiri Prince' .5.0...5.0
10B72002H. sp. (pinguifolia) .0.0...0.0
10B102002H. salicornioides 89.39 .0.00.0.0.00.0
10B132002Snow Wreath' .5.0...5.0
10B162002H. glaucophylla .0.00.0.0.00.0
10B192002Pimeba' .5.0...5.0
10B222002Red Edge' .0.60.0..0.3
10B252002Wiri Splash' .5.0...5.0
10B282003Pamela Joy' ..5.0.3.04.0
10B312003Tapawera' ..2.0.0.01.0
11A12003Gibby' ..0.0.0.00.0
11A42003H. pinguifolia 'Sutherlandii' ..0.0.0.00.0
11A72003Oratia Gala' ..0.0.0.00.0
11A102003Gnome' ..0.0.0.00.0
11A132003H. venustula (Mt. Hikurangi) ..0.0.0.00.0
11A162003H. buxifolia 'Minima' ..0.0.0.00.0
11A192003Edinensis' ..0.0.0.00.0
11A222003H. sp. (diosmifolia x townsonii) ..5.0..5.0
11A252003H. diosmifolia 'Prostrata' ..5.0..5.0
11A282003Autumn Snow' ..3.3.2.02.7
11A312003H. sp. (harperi) ..0.0.0.00.0
11B12003H. recurva 'Aoira' ..2.3.3.63.0
11B42003Greensleeves' ..0.0.0.00.0
11B72003H. 'Karo Golden Esk' ..0.0.0.00.0
11B102003Jasper' ..3.0.0.01.5
11B132003Julie Knight' ..0.0.0.00.0
11B162003H. buchananii 'Fenwickii' ..0.0..0.0
11B192003Christensenii' ..0.0.0.00.0
11B222003Parahebe linifolia 'Blue Skies' ..3.0.2.02.5
11B252003H. imbricata ..0.0.0.00.0
11B282003Snowdrift' ..5.0..5.0
12A12003H. evenosa ..4.3.0.02.2
12A42003Baby Marie' ..0.0.3.01.5
12A72003Geoff. Turnbull' ..4.3.2.53.4
12A102003H. glaucophylla 'Clarence' ..0.0.0.00.0
12A132003Hanna' ..3.0.0.01.5
12A162003County Park' ..0.0.0.00.0
12A192003Parahebe lyallii 'Baby Blue' ..2.6.2.02.3
12A222003H. acutiflora (Huka Falls) ..5.0..5.0
12A252003Spender's Seedling' ..1.0.1.01.0
12A282003Wiri Joy' ..4.3.2.03.2
12A312003Wiri Magic' ..5.0..5.0
12B12003Hidcote' ..4.0.5.04.5
12B42003H. rigidula ..3.0.0.01.5
12B72003Mauve Fingers' ..5.0..5.0
12B102003Christabel' ..0.0.0.00.0
12B132003Karo Golden Esk' ..0.0.0.00.0
12B162003H. sp. (Ilirilii) ..3.0.2.62.8
12B192003Veronica Lake' ..5.0..5.0
12B222003Heidi' ..2.5.2.52.5
12B252003H. pimelioides var. glauca 84.79 ..0.0.0.00.0
12B282003H. glaucophylla 'Korbel Pewter' ..0.0.0.00.0
12B312003Lindsayii' ..0.0.2.01.0
13A12003H. decumbens ..3.0.0.01.5
13A42003Oratia Beauty' ..3.0.0.01.5
13A72003Pinocchio' ..5.0..5.0
13A102003Midsummer Beauty' ..5.0..5.0
13A132003H. odora 'Baby Blush' ..0.0.0.00.0
13A162003H. topiaria 'Rosewarne' ..0.0.0.00.0
13A192003H. pubescens 90.486 ..5.0..5.0
13A222003H. rakaiensis ..0.0.0.00.0
13A252003Hobby' ..5.0..5.0
13A282003Nantyderry' ..0.0.0.00.0
13B12003B'limit' ..4.0..4.0
13B42003Wiri Image' ..3.0.0.61.8
13B72003Champagne' ..2.0.2.02.0
13B102003Bridget' ..5.0..5.0
13B132003H. parviflora 'Holdsworth' ..0.0.0.30.2
13B162003Parahebe catarractae 'Porlock Purple' ..2.3.2.02.2
13B192003Silver Dollar' ..0.0.0.00.0
13B222003Ettrick Shepherd' ..2.6.0.31.5
13B252003Gauntlettii' ..3.3.2.63.0
13B282003Wiri Dawn' ....2.02.0
13B312003La Favorite' 89.26 ..5.0..5.0
14A12003Otari Delight' ..4.6.3.03.8
14A42003Wiri Grace' ..3.0.1.52.3
14A72003Gloriosa' ..5.0..5.0
14A102003Dobbies Delight' ..5.0..5.0
14A132003H. albicans (Gouland Downs) ..0.0.0.00.0
14A152003H. dieffenbachii ..0.0.2.01.0
14A172004Marjorie' ....0.00.0
14A202004Boscawenii' ....4.64.6
14A232004H. venustula 'Patricia Davies' ....0.00.0
14A262004White Torrent' ....1.31.3
14A292004Rosie' ....1.01.0
14A322004Island Pass' ....0.00.0
14B12003Louise' ..5.0..5.0
14B42003Inspiration' ..5.0..5.0
14B72003H. sp. (procumbens) ..2.0.0.01.0
14B102003Simon Delaux' ..5.0..5.0
14B132003H. tetragona ..0.0.0.00.0
14B152003Veronica formosa ..2.0.0.01.0
14B172004White Heather' ....1.01.0
14B202004Fairlane' ....2.32.3
14B232004Dorothy Peach' ....1.01.0
14B262004Neil's Choice' ....2.02.0
14B292004Parahebe 'County Park' ..0.00.00.00.0
15A12004Purple Emperor' ....1.31.3
15A42004Joan Lewis' ....0.00.0
15A72004Purple Shamrock' ....2.02.0
15A102004H. elliptica 'Charleston' ....3.33.3
15A132004Joanna' ....1.01.0
15A162004Petra's Pink' ....2.02.0
15A192004Hinderwell' ....3.03.0
15A222004Hielan Lassie' ....0.60.6
15A252004Walter Buccleaugh' ..0.00.00.00.0
15A282004Edington' ....1.01.0
15A312004Headfortii' ....3.03.0
15B12004Jack's Surprise' ....3.03.0
15B42004Highdownensis' ....1.31.3
15B72004Fragrant Jewel' ....1.01.0
15B102004H. recurva 'Boughton Silver' ....1.51.5
15B132004Trixie' ....0.00.0
15B162004Cranleighensis' ....2.02.0
15B192004Mystery Red' ....0.50.5
15B222004Monica' ....0.00.0
15B252004Polden Hills' ....3.63.6
15B282004Bicolor Wand' ....1.01.0
15B312004Lavender Lace' ....3.03.0


Note that the names of the plants appear in the chart as they were received. Some of these names are invalid or were incorrect when the variety was obtained and have since been corrected. Others were assigned to distinguish unidentified varieties obtained from a source. Contact the author for information about the identity of individual plants.

Flowering

Flowering times of the Hebes in this trial were assessed monthly. Newly-planted Hebes are not assessed in the year of planting to allow for establishment. Flowering was rated on a 0-5 scale, with 0 meaning no flowers present and a rating of 5 given to those plants which are completely covered with blooms. The following chart shows flowering of the various clones in the trial. In many cases, flower data collection has been interrupted, or stopped, by cold weather affecting the plants.

 Flowering Times 
Plant NameJanFebMarAprMayJunJulAugSeptOctNovDecComments
528    XXX        
Alameda'    XXXXXX       
albicans (prostrate form)     XXX       
Alicia Amherst      XXXXXXXXXXXXXXX  
Amy     XXXXXXXXXXXXXXXXXXXXX 
Andersonii VariegataXXX     XXXXXXXXXXXXXXXXXX 
Anomala 'Purpurea'    XXXXXX       
Autumn Glory'     XXXXXX      
Autumn Snow'   XXXXXXXXX       
Baby Marie'   XXXXXX        
Beatrice      XXX      
Bicolor Wand'     XXXXXX      
Bishopiana Champagne      XXX     Tends to rebloom in Sept-Dec
B'limit'            No data
Blue Cloud     XXXXXX      
Blue Elf     XXX       
Blue Gem     XXX       
Blue Mist     XXX       
Boscawenii            No data
boughton dome            Has no flowered
Bowles Hybrid     XXX XXXXXXXXX   
Bracken Hill     XXX   XXX   
Bridget'            No data
buxifolia     XXX       
caledonia     XXX       
canterburiensis            No data
carnulosa    XXX       Blooms only after 4-5 years
Christabel'            Has not bloomed
Christensenii'            Has not bloomed
Clear Skies'     XXX      Data affected by Phytophthora problem
Coed     XXX       
County Park'            No data
Cranleighensis'     XXX  XXXXXX   
Cressit            Data affected by Phytophthora problem
Denise     XXX   XXX   
Diana      XXX      
Dobbies Delight            No data
Dorothy Peach'      XXX      
Edinensis            Has not flowered
Edington     XXX  XXX    
elliptica            No data
emerald gem            Has not flowered
Ettrick Shepherd     XXX       
Eveline     XXX       
Fairlane'     XXX      modest in bloom
Fragrant Jewel'     XXX       
franciscana variegata     XXX       
Gauntlettii'     XXX       
Gibby    XXX        
Glauca      XXXXXX     
Gloriosa'       XXXXXXXXX  Data incomplete because of cold damage
Gnome'            Has not flowered
Goeff. Turnbull'    XXX       winter injury affects results
great orme      XXXXXX    reblooms sporadically through October
Greensleeves'    XXX        
H. 'Affinis' 89.60            No data-winter killed
H. acutiflora (Huka Falls)         XXX  Data incomplete because of cold damage
H. albicans    XXXXXXXXX  XXX   
H. albicans (Gouland Downs)     XXX       
H. albicans 242-99     XXX       
H. albicans 83.120    XXXXXX  XXX    
H. amplexicaulis nbsp;  XXX       Not a strong bloomer
H. anomala    XXX       Not a strong bloomer
H. brachysiphon    XXXXXX      Sporadic rebloom in Fall and Winter
H. buchananii 'Fenwickii'            Data affected by plant dieback
H. buxifolia 'Minima'    XXX        
H. corriganii   XXX     XXX   
H. corriganii 91.663XXX  XXXXXX      XXX 
H. cupressoides 'Nana' 89.23            Has not flowered
H. decumbens    XXX        
H. dieffenbachii     XXX       
H. diosmifolia (Strybing H-15)     XXX       
H. diosmifolia 84.75            No data-winter killed
H. diosmifolia 'Prostrata'            No data-winter killed
H. divaricata 84.76     XXX       
H. elliptica            No data-winter killed
H. elliptica 'Charleston'    XXX    XXX   
H. elliptica 'Variegata' (Strybing H-13)            No data-winter killed
H. evenosa            No data-winter killed
H. gibbsii    XXX        
H. glaucophylla    XXX        
H. glaucophylla 'Clarence'     XXX       
H. glaucophylla 'Korbel Pewter'            Has not bloomed significantly
H. gracillima     XXX       
H. imbricata            Has not bloomed
H. 'Karo Golden Esk' (11B)            Has not bloomed significantly
H. macrantha 91.631    XXX        
H. macrocarpa 'Pink'      XXXXXXXXXXXXXXXXXXData incomplete because of cold damage
H. macrocarpa v. brevifolia            Data incomplete because of cold damage
H. macrocarpa v. brevifolia 84.78            Data incomplete because of cold damage
H. macrocarpa v. macrocarpaXXXXXXXXXXXX        Data incomplete because of cold damage
H. ochracea 'James Stirling'    XXX       Blooms only after 4-5 years
H. odora 'Baby Blush'    XXX        
H. parviflora 'Holdsworth'            Has not bloomed
H. parviflora v. angustifolia            Has not bloomed
H. pauciramosa var. masonae    XXX       Blooms sporadically throughout year
H. pimelioides var. glauca 84.79    XXX        
H. pinguifolia    XXX        
H. pinguifolia 'Sutherlandii'    XXX        
H. pubescens      XXXXXXXXX   Data incomplete because of cold damage
H. pubescens 90.486        XXXXXX  Data incomplete because of cold damage
H. rakaiensis     XXX       
H. recurva      XXX      
H. recurva 'Aoira'      XXX      
H. recurva 'Boughton Silver'      XXX      
H. rigidula (12B)     XXX       
H. rigidula (7B)    XXXXXX       
H. rupicola            Has not bloomed
H. salicifolia v. angustissima      XXX XXXXXX  Blooms sporadically in fall
H. salicornioides 89.39    XXX        
H. 'Silver Queen            Data incomplete because of cold damage
H. sp. (diosmifolia x albicans)    XXX        
H. sp. (diosmifolia x townsonii)            Data incomplete because of cold damage
H. sp. (elliptica x crassifolia)            Data incomplete because of cold damage
H. sp. (Halifax Hardy)    XXX        
H. sp. (harperi)      XXX      
H. sp. (llirilii)   XXXXXX        
H. sp. (odora var. prostrata)    XXX        
H. sp. (pinguifolia)    XXX        
H. sp. (procumbens)            Has not bloomed
H. sp. (unknown clone) XXXXXX         Data incomplete because of cold damage
H. sp. (venustula)     XXX       
H. sp. (Western Hills)     XXX       
H. sp. 84.86       XXX    Data incomplete because of cold damage
H. Speciosa 91.612            Data incomplete because of cold damage
H. speciosa 'Pink'      XXXXXXXXXXXXXXXXXXData incomplete because of cold damage
H. speciosa 'Violacea'        XXXXXX  Data incomplete because of cold damage
H. stricta v. lata      XXX      
H. Stricta v. macroura       XXXXXXXXX   
H. strictissima     XXX       
H. subalpina    XXX        
H. tetragona   XXXXXX        
H. topiaria 'Rosewarne'     XXX      Minimal bloom so far
H. townsonii 91.747            Data incomplete because of cold damage
H. traversii    XXXXXX      Data incomplete because of cold damage
H. venustula (Mt. Hikurangi)    XXX        
H. venustula 'Patricia Davies'            Has not bloomed
H. venustula 'Sky Blue'     XXX       
H. vernicosa    XXX        
haastii     XXX       
hagley park     XXXXXX      
Hanna'     XXX       
Hartii     XXX      Data incomplete because of cold damage
Headfortii'    XXXXXX       
Heidi'     XXX XXXXXXXXXXXXXXXData incomplete because of cold damage
heliohebe hulkeana    XXX       Data incomplete because plant dieback
Hidcote'      XXXXXXXXXXXX  Data incomplete because of cold damage
Hielan Lassie'     XXX       
Highdownensis'     XXX      Some rebloom in fall
Hinderwell'     XXXXXX XXX   Data incomplete because of cold damage
Hinerua     XXX      Only blooms after 4-5 years
Hobby'       XXX    Data incomplete because of cold damage
icing sugar     XXXXXX      
Inspiration            Data incomplete because of cold damage
Inverey     XXX  XXXXXX   
Inverey 89.18     XXX  XXXXXX   
Island Pass'            Has not bloomed
Jack's Surprise'     XXXXXX XXX    
jane holden      XXX      
Janet     XXXXXXXXXXXXXXXXXX May continue to bloom in winter
Jasper'            Has only insignificant bloom
Joan Lewis'    XXXXXX      Data incomplete because of cold damage
Joanna'     XXX       
Josephine      XXX      
Julie Knight'    XXX        
Karo Golden Esk' 12B            Has not bloomed
La Favorite    XXXXXX       
La Favorite' 89.26            Data incomplete because of cold damage
La Seduisante      XXXXXXXXXXXX  Data incomplete because of cold damage
Laingii 94.53            Has not bloomed
Lavender Lace'   XXXXXXXXX       
Lavender Spray     XXX       
Leonard Cockayne   XXX         
Lewisii     XXX   XXX  Data incomplete because of cold damage
Lindsayii'    XXXXXX      Not a strong bloomer
Lindsey White    XXXXXX       
little       XXXXXXXXX  Data incomplete because of cold damage
Loganioides            Has not bloomed
Louise'            Data incomplete because of cold damage
MacEwanii 83.380     XXX       
Maori Gem            Has not bloomed
margret     XXX       
Marjorie'     XXX       
Mary Antoinette'     XXX      Data incomplete because of cold damage
Mauve Fingers'         XXX  Data incomplete because of cold damage
mckean            Has not bloomed
Midsummer Beauty'        XXXXXX  Data incomplete because of cold damage
Monica'     XXXXXX      
Mount Stewart            Sporadically produces a few flowers
mrs winder     XXX      Flowers sporadically in summer and fall
Mystery Red'            Data incomplete because of cold damage
Nantyderry'    XXX        
Neil's Choice'     XXXXXX XXXXXX   
New Zealand Gold            Has not bloomed
nicolas blush     XXX  XXXXXX  Flowers sporadically into December
Obtusata            Data incomplete because of cold damage
Oratia Beauty'     XXX       
Oratia Gala'     XXX      Will flower sporadically into Fall
oswego     XXX  XXX   Flowers sporadically during Fall
Otari Beauty     XXX      Flowers sporadically during Fall
Otari Delight'            Data incomplete because of cold damage
pagei   XXX         
Pamela Joy'    XXXXXX      Data incomplete because of cold damage
Parahebe catarractae 'Porlock Purple'    XXX   XXXXXX   
Parahebe 'County Park'            Data incomplete because of cold damage
Parahebe formosa 90.178            Data incomplete
Parahebe lyallii 'Baby Blue'    XXX   XXXXXX   
parahebe olsenii    XXX        
Parahebe 'Snowcap'    XXX XXXXXXXXXXXX   
Parahebe linifolia 'Blue skies'    XXX  XXXXXXXXX   
Pascal     XXX      Flowers sporadically in Fall
patty's purple    XXX       Flowers sporadically later in summer
H. sp. ('Patty's Purple Variegated')            Data incomplete because of cold damage
paula            Data incomplete because of cold damage
Petra's Pink'    XXX        
Pewter Dome     XXX       
Pimeba            Data affected by plant dieback
Pink Fantasy      XXX     Flowers sporadically throughout Fall
Pink Paradise (PVR)XXX  XXXXXX    XXXXXXXXX 
Pink Payne      XXXXXXXXXXXXXXXXXX 
Pink Pearl      XXXXXXXXXXXXXXXXXX 
Pinocchio'            Data incomplete because of cold damage
Polden Hills'     XXXXXX      
powis castle blue     XXXXXX     Data incomplete because of cold damage
Primley Gem     XXX      Data incomplete because of cold damage
prince      XXX     Flowers sporadically throughout Fall
Purple Emperor'     XXXXXX      
purple picture     XXXXXX XXXXXXXXX  
Purple Pixie    XXXXXXXXXXXXXXXXXXXXX  
purple queen            Data incomplete because of cold damage
Purple Shamrock'            Has not bloomed
Purple Tip      XXXXXX    Data incomplete because of cold damage
Quicksilver     XXX      Data affected by Phytophthora problem
Red Edge            Data incomplete because of cold damage
Rosie'     XXX  XXXXXX   
salicifolia      XXX      
Sapphire     XXX       
Sarana     XXX  XXXXXX   
Sarnia     XXX  XXXXXXXXX May continue to bloom in winter
Silver Dollar'     XXX      Sparse bloom, prone to reversion
Simon Delaux        XXXXXX  Data incomplete because of cold damage
Snow wreath            Data incomplete because of cold damage
Snow Cover     XXX       
Snowdrift'            Data incomplete because of cold damage
speciosa     XXXXXXXXXXXXXXX  Data incomplete because of cold damage
speciosa variegata            Data incomplete because of cold damage
Spender's Seedling'      XXX XXX    
Squalida      XXX      
Strybing H-1     XXX      Data incomplete because of cold damage
Strybing H-10      XXXXXXXXXXXX  Data incomplete because of cold damage
Strybing H-12     XXX  XXXXXX   
Strybing H-14     XXX       
Strybing H-16     XXX       
H. sp. (Strybing H-17)            Has not bloomed
Strybing H-2            No significant bloom
Strybing H-3    XXXXXX       
Strybing H-4       XXX    Data incomplete because of cold damage
Strybing H-5      XXXXXXXXXXXX  Data incomplete because of cold damage
Strybing H-8      XXXXXXXXXXXXXXXXXXData incomplete because of cold damage
Strybing H-9     XXX XXXXXX    
Sussex Carpet     XXX       
Tapawera'     XXX       
topiaria    XXX       Not a heavy bloomer
traversii    XXXXXX       
tricolor            Data incomplete because of cold damage
Trixie'    XXX        
H. venustula 'Patricia Davies'            Has not bloomed
Veronica formosa     XXX       
Veronica Lake'            Data incomplete because of cold damage
Violet snow     XXX XXXXXX   Flowers sporadically throughout Fall
Walter Buccleaugh'            Has not bloomed
wardiensis    XXX        
White Gem     XXXXXX     Flowers sporadically throughout Fall
White Heather'     XXX       
White Torrent'     XXXXXX      
Wingletye'     XXX       
wiri charm     XXX       
wiri cloud    XXX       Not a heavy bloomer
Wiri Dawn'     XXX  XXX   Data incomplete because of cold damage
Wiri Gem     XXX      Data incomplete because of cold damage
Wiri Gem 94.56      XXX     Data incomplete because of cold damage
Wiri Grace'     XXX   XXXXXX  
wiri image     XXX       
Wiri Image'     XXX       
Wiri Joy'     XXX       
Wiri Magic'            Data incomplete because of cold damage
Wiri Mist    XXX        
Wiri Prince'            Data incomplete because of cold damage
Wiri Spears' 94.61            Data incomplete because of cold damage
Wiri Splash            Data incomplete because of cold damage
Wiri Vision            Data incomplete because of cold damage
youngii    XXXXXX       


Note that the names of the plants appear in the chart as they were received. Some of these names are invalid or were incorrect when the variety was obtained and have since been corrected. Others were assigned to distinguish unidentified varieties obtained from a source. Contact the author for information about the identity of individual plants.

Pests and Diseases

Few pest problems were noted in this trial. From time to time, spittlebugs can be seen on the plants in spring, but do no obvious damage.

Earwigs can burrow between the clasped leaves at shoot tips on large-leaved cultivars, and their feeding causes some leaf distortion, but this is sporadic and relatively minor damage.

Whiteflies may be seen on the plants, but this seems to be rare. Other common pests of landscape plants, like root weevils or aphids, were not observed.

Although they are far from a pest, it should e mentioned that honeybees and other pollinators are very attracted to Hebes. They are to be found on the flowers most times of the year when they are active, but are particularly noticeable in the fall when few other plants are in bloom. Large, fall blooming Hebes will be host to large numbers of honeybees on warm days in late September and October.

Diseases have been more problematic in this trial. The major disease problems have been Septoria leaf spot, Downy mildew and Phytophthora Root Rot. To find out information on management of these diseases in the PNW, see the Pacific Northwest Plant Disease Management Handbook.

Septoria leaf spot

This is a fungal disease caused by Septoria exotica. The disease causes small black spots on the leaves, which enlarge and form an ash-colored center. Individual leaves may have large numbers of these spots. The disease is particularly noticeable on large-leaved cultivars, but can be seen on smaller-leaved types as well.

The spots become obvious in the late fall and winter on the current seasons growth. The following spring, as the new growth emerges, those affected laves tend to fall off. Over several years, repeated cycles of infection and leaf loss causes a “leggy” appearance to the plant, which can sometimes be temporarily corrected by pruning. Although a formal evaluation has not been done, a wide range of Hebe cultivars seem to be susceptible to the disease.

Downy mildew

This is a fungal disease, caused by Peronospora grisea. The disease causes major leaf damage, leaf loss and shoot dieback, eventually it can cause plant death. The disease is usually noticed first by a yellowish, blotchy discoloration of the leaves, often on the lower leaves of the plants. This discoloration can affect large portions of individual leaves. Leaves become curled and distorted. On the underside of the leaves a grayish sporulation of the fungus may be seen.

Eventually the affected parts of leaves turn brown and shrivel. Plants can be entirely defoliated and killed.

This disease is a serious problem for cultivation of some Hebes in the landscape in the U.K. In western Oregon, it is generally not a problem for landscape shrubs in the Willamette Valley, assuming they are given sufficient light and air circulation. The only time it seems to occur in this area is if a Hebe is grown in too much shade in a moist environment. On the Oregon Coast, persistent summer fog can induce the problem in nursery or landscape situations.

Root rot

Both Phytophthora sp. and Fusarium oxysporum and been implicated in root rot problems of HebePhytophthora tends to be more of a problem in cold soil, while Fusarium is more common in warm soils. The disease is usually first noticed by the flagging of individual stems, often in mid-summer. Leaves on these stems turn yellow then brown. Entire sections or sides of the shrub may become affected quite rapidly, looking almost as though it were burned.

Plants may be stunted. Roots below affected branches are rotted. The entire plant may die, or it may persist for months in this state. Phytophthora in particular is more likely to be an issue in heavy-textured soil or poorly-drained sites. Amending these soils with organic matter and other amendments will improve soil aeration and reduce the likelihood of disease. Ensure the site is well-drained and water regularly but not to excess. Most established Hebes growing in good soil require water only 1-2 times per week for a few minutes from a typical irrigation system.

Drought tolerance

Hebes are often referred to as “drought-tolerant” shrubs and may be sold by retailers as such. However, even in the Pacific Northwest, summers are warm and dry enough to stress virtually all Hebes if regular summer water is not provided. This is particularly true of summer and fall-blooming cultivars, which bloom on new growth, and require regular water to continue growing, without which they will stop producing flowers.

How Hebes came to be regarded as “drought-tolerant” is a bit of a mystery, unless there is a tendency to associate evergreen plants in general with drought tolerance. The term “drought-tolerant” can mean a lot of different things, but if we use the definition, “a plant which will survive in the PNW entirely on rainfall without added summer irrigation”, then few Hebes will perform well under these conditions. The PNW is a Mediterranean-type climate, with a pronounced dry period of 3-4 months, and summer temperatures will exceed 90°F in the Willamette Valley on 14-21 days each summer. Almost all Hebes are from New Zealand, and therefore originate in a relatively mild, cool climate with at least some summer rainfall.

Kristensen (1989) classified Hebe species as to their origin in wet or dry habitats. About 1/4 of the listed species evolved in dry habitats. This includes familiar species like H. pinguifoliaH. carnosulaH. rakaiensisH. decumbensH. pimelioides and H. cupressoides. However, even the “dry” habitats received up to 60cm of rain per year. As a result, most of the available cultivars share this need for at least occasional summer water, depending on conditions. It is almost impossible to say what the water requirement of a particular cultivar will be, because many are of unknown parentage. Instead it will simply have to be planted and evaluated in the conditions characteristic of that site.

Symptoms of drought stress are expressed in a variety of ways. The first signs are typical of most plants and involve drooping of leaves and even shoot tips.

This is reversible if water is immediately provided. Repeated events like this will cause the leaf color in many Hebes to change from a glossy green to a pale, dull appearance, particularly on the older leaves.

 

Prolonged stress will cause yellowing of the foliage, and brown, necrotic areas will develop on the leaves, especially on the midrib.

 

The older leaves on the bottom and interior parts of the canopy will start die and fall off, in many cases giving the plant a “leggy” appearance.

 

Continued lack of water will cause dieback of portions of the canopy and eventually the entire plant.

Factors which will determine how much water a given Hebe will require are many:

Cultivar

Some Hebes do survive and grow well with limited water. Although evidence is scant, and based primarily on casual observation, in general blue-leaved Hebes seem to tolerate dryer garden conditions in the PNW than whipcord or large-leaved cultivars. Even these plants will still prefer a good watering every 7-10 days in the warmest part of summer and should not be planted with truly drought-tolerant Mediterranean plants like CeanothusCistus or Rosemary, which are best without summer water.

Site

The site will have a major impact on water requirement. Hebes planted in full sun naturally require more water than those in some shade. Plants on the south or west side of buildings will be particularly stressed from the added heat from the building. If protection from mid- to late-afternoon sun is provided, then water requirement will be reduced. Do not plant in full shade as this will result in poor growth and possibly foliar disease problems.

Soil

Soil is another important factor and all Hebes prefer a well-amended, well-drained soil for best growth. Heavy, compacted soils do not allow for good root growth of fibrous-rooted plants like Hebes and this will increase drought stress. Amendment of these soils with organic matter prior to planting is a good start. Mulching following planting, and avoiding foot traffic on the soil afterward, will help good structure to develop and improve conditions for root growth and water storage in the soil. For more information on soil amendment and mulching, see EC 1561, Improving garden soils with organic matter, or EC 1629-E, Mulching woody ornamentals with organic materials. Both are available from OSU Extension publications: http://extension.oregonstate.edu/catalog/.

Website creator

Neil Bell
Community Horticulturist
OSU Extension Service
Marion and Polk Counties
3180 Center Street NE #1361
Salem, OR 97301
Phone: 503-361-2671

References

Kristensen, L. 1989. The Genus Hebe-A botanical report. Danish Research Service for Plant and Soil Science. Report #S-2034.

Books and websites 

There are now several excellent texts on Hebes, which are essential for those concerned with correct naming of species and cultivars, as well as being sources of information on culture of these plants:

Bayly, M and A. Kellow. An illustrated guide to New Zealand Hebes. Te Papa Press.

Chalk, D. 1988, Hebes and Parahebes. Timber Press, Portland, OR. 152 pp. (out of print)

Hutchins, G. 1997. Hebes here and there. Hutchins and Davies, Reading, Berks. 320 pp.

Metcalf, L.J. 2001. International Register of Hebe cultivars. Royal New Zealand Institute of Horticulture. 232 pp.

Metcalf, L. 2006. Hebes: a guide to species, hybrids and allied genera. Timber Press, Portland, OR. 260 pp.

Wheeler, Chris and Valerie. 2002. Gardening with Hebes. Guild of Master Craftsman Publications. 160 pp.

Another fundamental source of information on Hebes is The Hebe Society, whose website has a wealth of information and links. http://www.hebesoc.org