Green gardening: Growing cauliflower

Of all Brassica genus vegetables, cauliflower is the most difficult to grow as it needs cool temperatures, a lot of moisture, and fertile soil. It does not withstand frost well yet it will not form a head in hot weather.

Soil requirements for cauliflower are much the same as for cabbage. If your soil is strongly acid, apply lime as far ahead of planting time as possible, preferably in the fall. Because a fertile soil is an absolute necessity for cauliflower, work in a five- to 10-centimetre (two- to four-inch) layer of mature compost or a three-centimetre (one-inch) layer of well-rotted manure.

The pure white colour of cauliflower that you are used to seeing is achieved by blanching — covering the head to shut out light that would turn the flower buds (called curds) to green. Blanching also preserves the cauliflower's delicate flavour.

Self-blanching varieties have tall leaves to shade the curd. Although most cauliflower is white, there are purple varieties that do not have to be blanched and are often recommended for home gardeners. They turn green when cooked and taste somewhat like broccoli.

New coloured varieties are appearing in nursery catalogues: Cheddar is orange-yellow, Graffiti is purple, and Veronica is green with spiky florets.

• Recommended early varieties of cauliflower: Snow Crown and Early Snowball
• Early or late crop: Violet Queen
• For late crops: Snowball and Self-Blanch Snowball

For spring plantings in most areas, start cauliflower seeds indoors, six to eight weeks before the last expected frost.

• Sow the seeds in individual pots, three or four seeds to a pot.
• When the seedlings emerge, snip off all but the strongest plant.
• Keep the seedlings in a sunny, cool spot.
• Two weeks before planting them outside, harden them off in a cold frame.

• Set out the seedlings at about the time of the last expected frost.
• Space the plants 40 to 60 centimetres (15 to 25 inches) apart, in rows 60 to 90 centimetres (25 to 35 inches) apart.
• To protect the young plants against cutworms, slip a cutworm collar around each plant. You can make the collars from paper cups with the bottoms removed.
• Cauliflower grows better in soil that is enriched regularly.
• Every three or four weeks, scatter an eight-centimetre (three-inch) band of complete fertilizer along each side of the row, being careful not to let it fall on the plants. Water thoroughly to soak the fertilizer into the soil.

Lots of water. Soil enrichment alone will not ensure a good crop. If cauliflower roots are deprived of water for even a short time, the plants will probably not form heads. Be sure that the bed receives a good soaking at least once a week, and mulch the ground with a thick layer of hay or half-rotted compost.

Blanching. As mentioned earlier, the head must be protected from the sun's rays to grow white. Watch for a small bud to appear at the centre of the plant. When the bud is 10 to 15 centimetres (four to six inches) in diameter, it is time to blanch the head. Draw the lower leaves of the plant loosely over the bud, and fasten them together with a piece of soft twine or a rubber band. Leave enough room inside this leafy bag for the head to grow to full size — 20 to 30 centimetres (eight to 12 inches) across.

The cauliflower head is ready to harvest when it is firm and compact.