Brassica Growing Basics

What counts as a brassica?

The group includes broccoli, cabbage, cauliflower, kale, collards, kohlrabi, Brussels sprouts and related crops. They share needs and share pests, so treat them as one family when planning rotation.

Do not plant brassicas where relatives grew in recent seasons. Ask your extension office how long to wait, since rotation helps manage disease that builds up in soil.

Brassicas need a firm seedbed, so avoid planting into soil that was just tilled fluffy. Walk the bed or press it down lightly before transplanting, and firm each plant in well so the roots contact soil.

When should I plant brassicas?

Most do best when they mature in cool weather. Transplants go in a few weeks before the last spring frost for many types, and again in mid to late summer for a fall crop. Ask your extension office for dates based on local frost data.

Heat can cause broccoli to bud early and cauliflower to turn out poorly. Count days to maturity back from the weather you want to avoid. A cold spring can push plants to bolt, so protect transplants with row cover on frosty nights and remove it on warm days so heat does not build up underneath.

Cutworms can clip young transplants at the soil line. A paper or cardboard collar around each stem at planting is a simple, low-cost protection, and checking plants in the evening helps you catch damage early.

• Spring crop: early transplants
• Fall crop: start in summer
• Check days to maturity
• Hardy kale: extends into fall

Should I start seed or buy transplants?

Transplants are easier for most gardeners. Choose stocky plants with healthy leaves, and avoid plants with roots circling heavily or yellow leaves. Harden off plants over several days before planting.

If you start seed, provide strong light and cool conditions indoors so seedlings do not grow thin and leggy.

Clubroot is a soil disease that can ruin brassicas and persist in soil for years. If you see swollen, distorted roots, ask your extension office before planting brassicas there again and do not move soil from affected areas.

• Stocky plants with healthy leaves
• No yellowing or spots
• Roots not tightly circling
• Hardened off before planting

How do I prepare soil and space plants?

Brassicas like fertile, well-drained, firm soil with near-neutral pH. A soil test shows whether you need to adjust pH, and liming decisions should be based on the test. Spacing varies by crop, so follow the packet.

Crowded plants make small heads and trap moisture. Set transplants a little deeper for cabbage family crops and firm soil around roots.

Plan the budget in categories: transplants or seed, row cover, soil test and amendments, and supports. Row cover is reusable for several seasons if handled gently, so it is one of the best long-term values.

• Firm soil with good drainage
• Test soil pH before liming
• Follow spacing on the label
• Plant slightly deeper at transplant

How much water and feeding do they need?

Steady moisture matters, especially as heads form. Uneven water can split cabbage heads. Mulch to hold moisture and cool soil.

Brassicas are heavy feeders, so a side-dressing partway through the season is common. Follow your soil test and the label, since too much nitrogen can reduce quality.

Fall brassicas often taste sweeter after light frost. Ask your extension office for the typical first frost date and how much cold each crop tolerates, then decide when to cover or harvest.

What pests should I expect?

Cabbage worms, aphids, flea beetles, root maggots and slugs are common. Floating row cover set at planting protects plants and is one of the most effective measures. Check undersides of leaves weekly.

Hand-pick caterpillars, and ask your extension office about any control product, following the label strictly.

• Green caterpillars on leaves
• Tiny holes from flea beetles
• Aphids in head crevices
• Slugs on lower leaves
• Wilted plants with swollen roots

When and how do I harvest?

Cut broccoli heads while the buds are tight and before yellow flowers show, and side shoots often follow. Harvest cabbage when heads are firm. Cauliflower may need leaves tied over the head to keep it white, depending on variety.

Kale leaves can be picked from the bottom up through fall. Refrigerate promptly. Remove plant debris after harvest to reduce overwintering pests. Leave a few plants in the ground after the main harvest if your extension office says they are hardy locally, since many produce side shoots or tender leaves well into fall.

Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.