How to Plant, Grow, and Save Seeds from Cauliflower (Brassica oleracea)
Cauliflower belongs to the species Brassica oleracea, which also includes broccoli, kale, Brussels sprouts, and cabbage. Like other Brassica crops, cauliflower requires a generous amount of space in the garden to grow, especially in its second year of growth.
Figuring out the best time to start cauliflower plants can be challenging. Plants prefer consistent, cool weather (60 °F is ideal) and will not produce a full head if temperatures are too high. Days to maturity can also vary greatly from 55-100 days.
Cauliflower plants are regularly started in flats and subsequently transplanted to the garden. Start seedlings indoors at least 4-6 weeks before your expected transplant date. Sow cauliflower seeds ¼” deep. Seeds will germinate in 3-10 days. Space cauliflower 24” apart in the garden.
Northern gardeners may transplant seedlings to the garden in the early spring after danger of hard frost has passed, or try a late summer planting for a fall harvest. Southern gardeners will find success growing plants anytime in the fall and winter when hard frost can be avoided and temperatures are consistently cool.
Cabbage butterfly, cabbage looper, and flea beetles are common garden pests for cauliflower. Cauliflower can also suffer from downy mildew, black rot, and several other diseases. Cauliflower, like broccoli and other Brassica crops, can be protected with row cover to prevent early damage from pests such as flea beetles.
Cut cauliflower heads from the plant when they are large and firm. If left too long on the plant, cauliflower heads can become off-colored and mushy. Blanching, or wrapping the developing head with the plant’s own leaves, can help prevent discoloration.
Eating and Storing
Cauliflower can be enjoyed fresh, steamed, roasted, stir fried, and pureed. It is an incredibly versatile vegetable that is also great to blanch, freeze, and store for winter. Fresh cauliflower heads will store in the refrigerator for several weeks after harvest.
Cauliflower is a biennial plant. Biennials typically do not flower in their first growing season. They must first experience an extended period of cold weather before they flower, set seed, and die in their second growing season.
To ensure viable cauliflower, save seeds from at least five plants. To maintain a variety over time, save seeds from between 20-50 plants.
If your region does not regularly experience temperatures below 35 °F, try overwintering cauliflower outside in the ground. In this case, time planting so that plants have only formed small, loose heads when the growing season ends.
When plants cannot be successfully overwintered in the garden, they can be vernalized in storage. First, time planting so that plants have fully formed heads at the time of lifting. Take care to dig up the entire plant, roots and all. Then, trim off loose leaves, but be sure to leave the heads intact. Trimmed plants should be replanted into containers filled with slightly moist potting mix or sand for storage.
The optimum storage conditions for cauliflower vernalization ranges from 34-39 °F and 80-95% relative humidity. A traditional root cellar is ideal for this but garages, sheds, and other unheated structures work well in some climates.
In the spring, when the soil can be worked, replant cauliflower in your garden, taking care to give them a lot of room to resume growing and to flower. In their second year, increase Brassica spacing to 18-24” in rows that are at least 36” apart. Staking the plants is recommended.
After flowering in their second year of growth, mature seed pods become dry and turn brown as the seeds inside also mature and brown. As with many of the Brassica crops, the window of time for an optimal harvest may be short as mature pods will begin to shatter and bird predation can become a problem.
Seeds can be gathered by cutting entire branches or by harvesting whole plants. Because of this species’ tendency to shatter, the harvested material should be placed on drop cloths or in containers to prevent seed loss.
Branches of mature fruits can be threshed by rubbing the pods between one’s hands or by hitting the brittle pods against any surface that will cause fruits to break open. If the pods are dry, they will release their seeds easily when threshed.
Store cauliflower seeds in cool, dark, and dry places and always keep them in an airtight container to keep out moisture and humidity. Properly stored cauliflower seeds will remain viable for several years.