Manage Temperature To Avoid Buttoning
Many gardeners experience "buttoning" of cauliflower heads in the spring. This is a failure of the cauliflower head to gain in size after it reaches about an inch or less in diameter. It is usually due to transplant stress or heat stress during the head formation period or a lack of fertility or water, or the use of transplants with poor root growth or rootbound transplants.
One approach to protecting the cauliflower from buttoning is to cover the seedlings with fleece as soon as they are planted outside. Fleece will buffer air temperature shifts and keep the plants warmer when the air temps go down towards 50 degrees. Take the fleece off when all chance of frost is gone and air temps are mid-sixties or higher.
Optional – Instead of leaving the plants uncovered, set up shade cloth a few inches above the cauliflower until they are harvested.
BLANCHING OR KEEPING CURDS WHITE
If cauliflower heads are left exposed to the sun during their growth they will turn color to a light brown; not as attractive on the dinner table. So to keep the curds nice and white, you will pull some leaves over the curds to shade them from the sun. This is called blanching. Blanching is not needed on green, purple or self blanching varieties cauliflower.
Wait until the head reaches about 2 inches (5 cm) in diameter and starts pushing through the inward-curving leaves that cover it. You can then tie the outer leaves loosely over the head with a rubber band, or better, simply bend four or five of the large, outside leaves over the crown, then tuck the leaf tip into the opposite side. If the leaves partially snap while bending, that's OK. Bend a few more leaves over the following week if the head needs more coverage as it expands. The head will reach harvestable size in 2 to 14 days, depending upon the temperature; cool weather may slow head development.
Roots of cauliflower are shallow, so irrigation should be more frequent but lighter than for deeper rooted crops; but too light. Wet down two to three inches. Water immediately after transplants are set and whenever the soil surface begins to look dry. An even moisture supply is needed for transplants to become established and to produce good heads. An organic mulch will help keep soils cool and moist, and feed the soil food web. Apply 1 to 1.5 inches of water per week between you and the rainfall.
Avoid over-irrigating, as poor drainage as well as lack of water is harmful.
Inadequate moisture may cause small cauliflower heads to form prematurely.
Cauliflower is a heavy feeder and requires a rich soil. It is wise to add some slow release organic granulated fertilizer to the site where you plan to set the cauliflower plants maybe a week or two before planting. Work the fertilizer down two or three inches into the soil
In midseason you should apply a side dressing of the same fertilizer; a light handful around the stem of each plant. The optimum pH range for cauliflower is between 6 and 6.5. Liming the soil will increase the pH of acid soils. Use a soil test to determine if any special fertilization or liming is required.
Cauliflower of all the vegetables needs a layer of organic mulch for the entire growing season. This plant prefers cool soil and organic mulch keeps the soil five or six degrees cooler than uncovered soil.
Month to Month Care for Cauliflower
Month of March – If you want to use seeds instead of seedlings from the garden center, start seeds indoors six to eight weeks before the last frost date.
Month of April - Seedlings should be at least four weeks old and have two to four leaves and a stem half as thick as a pencil. Plant them about two to three weeks before the expected last frost date for your area. Mix slow-acting granular fertilizer into the soil when you prepare the planting area. Dig holes in the planting bed about 15 to 18 inches apart--further if you want the largest possible Cauliflower heads.
While they can handle cool weather, it is best to protect them from a surprise late frost. Be prepared to cover the tender plants temporarily with white polyspun garden fleece, newspaper cloches, or a cold frame.
Month of May - Cauliflower needs to have 2 to 3 inches of organic mulch to help keep moisture in the soil and keep the soil cool.
Curds exposed to light while forming tend to yellow, but this does not affect eating quality. As cauliflower plants begin to mature and the head or curd starts to form, gather together and tie the leaves over the curd with soft twine or tape. This "blanching" is required to ensure the curd will be white and tender at harvest. There are some 'self-blanching' types available where the leaves curl naturally over the head when grown in cool weather. However, some tying of the leaves may still be necessary.
Optional – Cauliflower will benefit from being covered by shade cloth starting in mid-May.
Optional - consider feeding the plants with organic liquid fertilizer about three weeks after planting.
Month of June – If cauliflower must be stored for several weeks before using, leave a portion of the stalk and leaves to protect the curd. Cauliflower will keep fresh in the refrigerator for up to two weeks.
Optional - If temperatures reach the 80’s before you harvest all your Cauliflower, spread shade cloth over the Cauliflower plants to keep them a bit cooler and encourage more growth.
Optional Fall Crop - Plan to start harvesting at least a month before killing frost in your area, so start new seedlings in June or early July. Using shade cloth over the seedlings in the first 6 to 8 weeks helps produce stronger plants in the fall.
Month of July – If you want to grow a fall crop, early July is the time to start seedlings. See the procedure above in the planting section
Month of August - If you have a fall crop going, you will do well to protect your seedlings with shade cloth. See planting section above for details.
Month of September – Watch to be sure your fall cauliflower is getting a steady but not excessive amount of water; about an inch a week from you and the rain.
Month of October – Time to harvest.