Overwintering Cauliflower for Spring Harvest (1978-1979)

Several of the coastal and marine-influenced valleys of the Pacific Northwest appear to have a suitable climate for overwintering cauliflower for spring harvest. Research on variety adaptability and cultural methods has been limited and commercial production has been primarily restricted to a few acres in the northern Willamette Valley, the Puget Sound area, and the Skagit Valley. The single greatest limiting factor has been a lack of proven cold-hardy varieties with acceptable curd quality. Research on overwintered cauliflower at the North Willamette Station commenced in 1977 and has focused on three areas: 1) finding adapted varieties, 2) determining the proper planting dates, and 3) determining proper fertilizer rates.


Methods employed varied with specific experiments, but the following fertilizers and pesticides were used in most trials and have proven acceptable. Most trials were transplanted into fields with a soil pH of about 6.0 and which had received a broadcast application of 700 to 1,000 pounds/acre of 10-20-10, 1,000 pounds/acre of dolomite, and one pound/acre of born. The only herbicide used was trifluralin at 0.75 pounds/acre; the most common soil insecticide program was fonofos incorporated at two pounds/acre followed by diazinon drenches if necessary for cabbage maggot control. No other insecticides were found necessary and fungicides were not used. Most plots were planted at three foot by 1.5 foot spacing. All treatments were randomized.

Further spring applications of nitrogen were made as discussed below. Plots were harvested at least twice a week from maturity of the first head.

Results and Discussion

I. Variety Evaluation
At least limited variety trials have been conducted each year since 1977. In general, the varieties heading in April were the most successful. The varieties Armado April and Armado Quick were superior in yield, quality, and hardiness. Subsequent trials have tended to reaffirm their superiority. In addition, the variety Preminda (or Primo) has also proven well-adapted to the Willamette Valley. Late varieties, which are exposed to higher temperatures, greater light intensity, and greater insect and disease pressures, have lower curd quality and smaller heads than the earlier varieties. Heads were not tied in these trials and discoloration of curd on late varieties may be prevented by this practice. Curd color of the early varieties is excellent but depth and density of the head is low. However, at least one Willamette Valley processor has found the quality acceptable for processing. Fresh market potential of the early varieties appears to be excellent.

II. Planting date
One of the major advantages of winter cauliflower is the suitability for double cropping. In the Station research program we were interested in varieties and planting dates which would allow for a second crop both before planting and after harvest. Planting date affects yield and quality in two ways: winter hardiness and size of plant at time of head formation. Early planting dates produce larger plants capable of producing high yields but early plantings are also more susceptible to winterkill (Table 8). Total yield of Armado April was highest at the second planting date since the larger plants from the first planting date suffered greater freezing and ice damage. Subsequent trials indicate that a transplant date near September 1 is optimal at the Station. Earlier dates may be better in areas with milder winter temperatures. The proper planting window will have to be determined for each potential growing area.

Planting date has relatively little effect on date of maturity. Trials separated by as much as one month at transplant have reached peak maturity no more than one week apart.

III. Winterkill
Most of the common winter cauliflower varieties have been considered hardy to about 18°F. However, many of the more recent F-1 hybrids have survived temperatures of 10°F at the Station. Planting in areas with expected winter low temperatures below 10°F risks losing the entire crop. For example, with the variety April, the following mortality rates were observed in the Willamette Valley in 1979: Station, 11°F, 10%; 4 miles SW of Station, 9°, 25%; 12 miles S of Station, 0°, 80%.

IV. Spring Nitrogen Application
Winter cauliflower has consistently responded to spring nitrogen application with increased yield, greater head size, and better foliage cover of the curd. Greatest yields have been obtained with sidedress application of 100 pounds/acre of N in early February and again in early March.


Winter cauliflower appears to have potential as a significant crop west of the Cascades. Areas normally free of ice storms, heavy snowfall, and with expected winter lows above 10°F are suitable. The potential exists for double cropping winter cauliflower with other early maturing crops with compatible pesticide and herbicide programs. Production costs for winter cauliflower should be lower than for autumn-harvested since insect problems are minimal and irrigation is unnecessary after plants are well established.

  Table 8. Effect of Transplant Date on Yield, Mean Head Weight, and   Winterkill of Cauliflower, 1978-79                                  Transplant                 Yield    Head Weight     Percent dead  date       Cultivar     (tons/acre)   (pounds)         plants       8/21/78    Armado April     8.2         1.5              31   8/21       Armado Quick     8.5         1.3              16   9/12       Armado April    11.7         1.4               5   9/12       Armado Quick     6.5         1.0               8  9/26       Armado April     8.7         1.2               8   9/26       Armado Ouick     6.8         0.9              13