Overwinter Leek Variety Trial, 1984-1985

Extremely high quality leeks are being produced on a small scale in the Willamette Valley with good yields. The crop is usually seeded in early spring, matures in autumn, and can be held through the winter for harvest the following spring. Very few varieties are grown commercially and the highest quality plants have been transplanted and grown in trench culture. The most lucrative market is the restaurant trade, which demands long, thick, blanched stems. Healthy foliage can also be used decoratively in presentation of restaurant dishes. This trial had two purposes, to evaluate a number of varieties in a late spring planting for overwinter harvest, and to evaluate several winter hardy varieties in a late planting for overwinter harvest. Growers would benefit if planting of the overwinter crop could be delayed, allowing the possibility of double cropping with a short season crop and reduced weed control problems. This report includes data from two harvests each of spring and summer plantings made in 1984 and harvested in the spring of 1985.


Nine leek varieties were seeded in flats on a greenhouse bench on March 23, 1984, and seven were seeded on June 6. The plot area received a broadcast application of 1,000 pounds/acre of 10-20-10, followed by formation of raised beds with 18-inch tops, 40 inches furrow to furrow, and about 7-inch height. Seedlings were transplanted on May 31 and July 31, respectively, into holes dibbled approximately 4 inches deep on 6-inch spacing, with two rows/bed. A single plot consisted of 20 feet of bed (80 plants). Treatments (varieties) were replicated 3 times in randomized complete block design. Propachlor herbicide was applied at 4 pounds/acre after planting and was reapplied on June 29, July 31, and October 8. The plots were also hand-hoed twice during the summer. An additional 25 pounds N/acre as nitroform was applied on July 6 and again on August 31. Twenty plants were harvested from each plot of the early planting on August 24 and on October 8. Harvested plants were topped 2 inches above the growing point (base of leaves).

An additional 50 pounds N/acre as nitroform was applied on February 13, 1985, along with propachlor, chlorpropham and fluazifop-butyl herbicides. Both plantings were harvested on March 8, 1985. The late planting was harvested a second time on May 7.


At the first harvest in August 1984, all plants were somewhat immature and did not differ significantly in weight/plant, blanched stem length, or stem width (Table 1). Often there appeared to be more variation between blocks than between varieties. Stem length did vary significantly with variety, with Conqueror and Acadia the shortest and Tivi the longest. All stems were slightly bulbed at the root end; color was light blue-green for all varieties.

At the second harvest of the early planting, all varieties had produced mature, marketable plants. Mean leek weight did not vary greatly with variety, except that Conqueror was lighter and Argenta heavier than most other varieties (Table 2). Stem length varied considerably among varieties, with Tivi, Bluvetia, and Kilima producing longer stems and Conqueror and Electra shorter stems. Blanch length did not vary significantly and appeared to be mostly controlled by transplanting depth. Stem width also varied little with variety, with great variability within a variety.

Differences in growth habit and foliage color were very evident by the second harvest. Acadia and Conqueror had the darkest blue foliage; Argenta, Bluvetia, Kilima, and Tivi had pale, green foliage, with the other three varieties intermediate in color. Tivi plants were tall and upright; Electra and Kilima plants were taller than average but with less upright foliage. Alaska and Conqueror had the shortest leaves. All varieties were judged of acceptable quality, with the blue-foliage plants more attractive.


Table 29. Leek size on August 24, 1984, 85 days after transplanting, early planting  Variety        Stem wt.     Stem lengthZ    Blanched lengthY   Stem widthX  _______________________________________________________________________________________________________________                  ounces      ----------------------inches----------------- 	  Acadia           4.3             3.3              2.2             1.2  Alaska           3.6             3.5              2.3             1.0  Alberta          4.4             4.0              2.8             1.2  Argenta          4.7             3.8              2.8             1.2  Bluvetia         4.6             4.0              2.2             1.2  Conqueror        4.0             3.2              2.0             1.0  Electra          4.9             3.5              2.0             1.3  Kilima           4.8             3.7              2.1             1.3  Tivi             5.1             4.3              2.5             1.3     LSD(0.05)      NS             0.7               NS              NS                ZMeasured from base of bulb to point of leaf branching.   YMeasured from base of bulb to mean extent of white area.   XMeasured just above the bulb.      Table 30. Leek size on October 8, 1984, 130 days after transplanting, early planting  Variety       Stem wt.       Stem length       Blanched length        Stem width                    ounces         ----------------------inches-----------------------  Acadia         7.9               4.7                 2.5                   1.5  Alaska         7.4               3.9                 2.4                   1.4  Alberta        8.4               3.9                 2.6                   1.4  Argenta        9.9               4.5                 2.9                   1.6  Bluvetia       8.2               5.2                 2.1                   1.4  Conqueror      6.4               3.3                 2.5                   1.4  Electra        7.6               3.5                 2.5                   1.5  Kilima         9.0               5.1                 2.1                   1.6  Tivi           8.4               5.2                 2.6                   1.4    LSD (0.05)   2.5               0.6                  NS                    NS           Table 31. Leek size on March 28, 1985                                                                    Early planting                          Late planting             Variety   Stem wt.   Stem length   Stem width   Stem wt.   Stem length   Stem width             ounces    ---------inches---------    ounces    ---------inches---------  Acadia      12.2         4.2           2.0         3.2         3.7           1.0  Alaska      11.7         4.3           1.8         3.2         3.3           1.0  Alberta     12.5         4.6           1.9         2.7         3.7           0.9  Argenta     14.0         5.0           1.9         4.2         4.0           1.1  Bluvetia    13.0         5.3           1.9          -           -             -  Conqueror   11.9         4.0           1.8         3.5         3.0           1.1  Electra     14.7         5.2           1.9         3.8         2.8           1.1  Kilima      15.0         7.3           1.9          -           -             -  Tivi        14.2         7.2           1.8          -           -             -    LSD(0.05)  NS          1.2            NS          NS         0.8            NS          Table 32. Leek size on May 7, 1985, late planting                             Variety      Stem wt.   Stem length   Stem width   Comments                                 ounces    ---------inches---------	  Acadia          5.1       4.2             1.3      bulbed, bolting  Alaska          4.7       3.8             1.3      pronounced bulb, bolting  Alberta         4.8       3.7             1.2      bulbed, bolting  Argenta         5.3       4.7             1.3      slightly bulbed, bolting  Conqueror       4.8       3.7             1.2      bulbed, bolting  Electra         5.4       3.7             1.3      slightly bulbed, bolting     LSD(0.05)     NS       0.3              NS                                 

The early planting overwintered nicely. All varieties had excellent size when evaluated on March 28, had not yet bolted, and the stems were not woody. Mean stem weight increased by 50 percent or more, because of increased diameter and length (Table 3). Kilima and Tivi had the longest stems, but were not significantly heavier than the other varieties. These two varieties also had a less desirable light blue-green color.

Only varieties suggested by the seed companies to be very winter hardy and bolting-resistant were included in the late planting. At first harvest on March 28, 1985, most varieties had longer stems than the industry standard, Electra, but were not heavier or thicker. All varieties were somewhat immature at this harvest.

At the May harvest of the late planting, all varieties had bolted, even though the stems were still somewhat small. This indicates that the July 31 transplanting date was too late. To successfully overwinter, plants must be set out early enough that mature stems are formed in the fall.

This trial indicates that of the several varieties available, none significantly outperforms the popular variety Electra. Transplanting should probably occur no later than June for either fall or overwintered harvest. The dibble planting method was acceptable, but did not produce blanch length equal to that of trench culture.