Brassicas: How to Grow the Cabbage Family, From Kale to Radishes

Brassicas are the cabbage family (Brassicaceae), also sold as cole crops: broccoli, cabbage, cauliflower, kale, collards, Brussels sprouts, kohlrabi, turnips, rutabagas, radishes and arugula all belong to it. They share three things that shape how you grow them. They are cool-season crops: Penn State puts their comfort zone at 60 to 65 F, so they go in for spring and fall rather than midsummer. They share soil diseases, so they rotate as one group: rotation gaps in our sources run from skipping one year (Penn State) to 4 years (Minnesota), and 5 to 7 or more as a clubroot control (UMass, a grower fact sheet; Cornell, for commercial growers). And they share pests, chiefly flea beetles and cabbage worms.

For the fall crop, the best row covers open with a fabric made for light frost on fall greens.

What counts as a brassica

Penn State Extension calls the cole crops members of the family Brassicaceae, once named Cruciferae for its cross-shaped flowers; "cole" traces to the German word for cabbage. That is why the same plants turn up under four names: brassicas, crucifers, cole crops and the mustard or cabbage family.

• Grown for heads or flower buds: cabbage, Brussels sprouts, broccoli and cauliflower (Penn State).
• Grown for leaves: kale, which Penn State calls a cole crop that never forms a head, and collards, which Maryland lists among the cole crops.
• Grown for a swollen stem or root: kohlrabi, turnips and rutabagas, and radishes, which Maryland places in the cabbage family.
• Salad greens: arugula, which Cornell lists under Brassicaceae.

The family line matters more than the shape of the plant. A radish and a cabbage look nothing alike, but the cabbage worm hosts Maryland lists include both, and UMass names radish among the crops clubroot attacks.

What you'll need for brassicas

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  Most gardeners set out spring transplants, started indoors four to six weeks ahead.

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When to plant brassicas: a cool-season family

Plant brassicas so they grow through cool weather and finish before or after the summer heat: Penn State says they thrive at 60 to 65 F and calls them early spring and fall crops. Heat hurts the parts you eat. Minnesota says hot weather, 86 F in the day and above 77 F at night, can leave broccoli with no crown, and that cabbage seeded late in spring matures in the hottest weeks with poor quality.

• Spring: most gardeners set out transplants, says Penn State, because the seed is tiny and fiddly; Penn State looks for a stocky, hardened-off transplant of five or six weeks. Minnesota starts cabbage indoors four to six weeks ahead of setting it out.
• Fall: Minnesota sows fall cabbage in the garden in early July and starts fall broccoli during July, so heads form as the weather cools, and Penn State plants cauliflower in late July or early August to harvest before autumn frost. Those are each state's own calendars; your frost dates set yours, and each linked guide below turns its crop's timing into dates for four sample towns.
• Cold, wet soil slows them down (Penn State), so an early start gains little in a soggy bed.

How much frost brassicas take

Most brassicas ride out frost, but not equally. Oregon State lists kale, collards, cabbage, Brussels sprouts, kohlrabi, broccoli, turnip, rutabaga, radish, arugula and mustard greens among vegetables that withstand a heavy frost, below 28 F, while cauliflower and Chinese cabbage are semi-hardy, taking only light frost, 28 to 32 F. Penn State, for home gardens, says most cole crops withstand a frost but do poorly in warm weather, and that Brussels sprouts come through repeated frosts and even early snow. Minnesota has broccoli growing on after the first light fall frosts.

Each row keeps the scope its source states. Penn State adds that a fall frost improves the flavor of kale and Brussels sprouts.

Brassica crop rotation: how many years

Rotate the whole cabbage family as one crop. Our sources disagree on how long, and count differently: Penn State says not to plant a cole crop where any brassica grew the year before and prefers a three-year rotation; Minnesota says four years for the crops it names; UMass advises 5 to 7 years between brassica crops against clubroot, and Cornell says, as a clubroot control, that at least 7 years away from susceptible crucifers may work. Penn State's three-year rotation, in our reading, brings a brassica back in the third season, while Minnesota asks for four seasons without one. In our reading, a 3- to 4-year cycle is the home-garden baseline, and the longer gaps suit beds where clubroot has turned up.

Two practical points follow. Radishes and arugula count: they are in the family, so a spring radish row in last year's cabbage bed is not a break, in our reading of the sources above. And weeds count too: UMass says clubroot can also infect mustard-family weeds, and Cornell's long rotation only works with those weeds kept out. Use the flow below to place this year's brassicas.

Pests the cabbage family shares

The same few insects follow brassicas from crop to crop, and seedlings take the worst of it. Minnesota names flea beetles, the leaf-eating caterpillars of three moths and butterflies (imported cabbage worm, diamondback moth, cabbage looper), and cabbage maggots in the roots among the many insects that feed on its cabbage and broccoli; it adds swede midge as a new pest in that state.

• Flea beetles chew small round holes, usually under 1/8 inch, and seedlings started from seed suffer more than transplants (Minnesota). For home gardens, Minnesota suggests row covers while seedlings grow, or an early-planted trap crop of a favored plant such as radish, which you then spray with a labeled pesticide once the beetles are feeding on it. Its separate advice for farms sows the trap crop ahead, typically by 7 to 14 days, and notes studies suggesting a trap of three brassica species beats one or two. By the 4- or 5-leaf stage in summer, plants are usually strong enough to survive the feeding.
• Imported cabbageworm, the green caterpillar of the small white butterfly, feeds on kale, collards, radish, turnip, cauliflower, Brussels sprouts, broccoli and cabbage (Maryland). Floating row cover stops the egg laying, hand-picking works on small plantings, and Maryland says the worms favor kale, turnip and rutabaga less than other hosts.
• Cabbage looper moves in from the south on storm fronts and builds up from May in Maryland; early-maturing plants take less damage, and Maryland suggests row cover where it is a yearly pest.
• Cabbage maggots feed on the roots and can kill plants (Minnesota).

Pollen-rich flowers draw in the predators that keep caterpillar numbers down (Maryland). For trap-crop pairings with these pests, see our companion planting chart.

Clubroot and other brassica diseases

Clubroot is the disease that makes brassica rotation matter. It swells roots into galls, so plants stunt, and they may yellow and wilt on warm days, and it lives in soil for years: UMass says its resting spores stay viable for up to eighteen years, and Cornell says 7 to 10 years or longer. It favors cold, wet soil with a pH under 7.0 (UMass) and travels mostly on infected transplants, soil on tools and boots, and runoff water; Cornell notes it is not carried on seed.

• Who gets it worst: in Cornell's Northeast grouping, cabbage, Chinese cabbage and Brussels sprouts are most susceptible, and broccoli, cauliflower, kale, collards, rutabaga and kohlrabi sit in the middle group. Turnips and radishes vary by variety: Cornell puts some turnips in the most susceptible group and some radishes among the very resistant.
• What growers do: keep transplants clean, improve drainage, keep mustard-family weeds out and raise soil pH with lime (UMass). Cornell's lime program targets pH 6.8 in infested fields and warns that limestone alone will not control the disease; those are farm-scale steps, so in our reading a home gardener should test the soil before liming a bed.
• Other diseases: Minnesota lists Alternaria leaf spot and black rot, which leaves yellow triangles at leaf edges, on cabbage and broccoli.

Brassica guides: the members of the cabbage family

Each linked crop below has a full guide of its own, with its own planting dates. The note beside each crop is our pick of one or two things to watch for, from the sources above; some are family traits and some are notes on that member alone.

Sources we used

We read each of these pages in October 2026. Where two disagree, both appear above with the scope each one states.

• "Penn State Extension: Cole Crops for the Home Vegetable Garden"
• "University of Minnesota Extension: Growing cabbage in home gardens"
• "University of Minnesota Extension: Growing broccoli"
• "University of Minnesota Extension: Flea beetles"
• "University of Maryland Extension: Imported Cabbageworm on Vegetables"
• "University of Maryland Extension: Cabbage Looper on Vegetables"
• "University of Maryland Extension: Growing Radishes in a Home Garden"
• "UMass Amherst Extension: Brassicas, Clubroot"
• "Cornell Vegetable Program: Clubroot of Crucifers"
• "Cornell Garden-Based Learning: Arugula growing guide"
• "Oregon State University Extension: Plant cold-hardy vegetables now for a spring harvest"

Related guides

• Fungus gnats, a pest of the seed trays that spring cabbage-family transplants start in
• Mint in pots, an herb with a cabbage moth reputation that field research has not borne out (WSU)
• Rosemary, among the herbs Penn State says can draw the wasps that parasitize diamondback moth larvae
• Kale growing guide
• Cauliflower growing guide
• Best grow lights for seedlings, for spring transplants started indoors
• Radish growing guide
• Arugula growing guide
• Turnip and rutabaga growing guide
• Companion planting chart

Frequently asked questions

What vegetables are brassicas?

Broccoli, cabbage, cauliflower, Brussels sprouts, kale, collards, kohlrabi, turnips, rutabagas, radishes, arugula and mustard greens. Penn State calls the family Brassicaceae, formerly Cruciferae, and calls its members cole crops.

How long should brassicas be rotated?

The sources range from skipping one year, with three years preferred (Penn State), to 4 years (Minnesota). Against clubroot, UMass (a grower fact sheet) lists 5 to 7 years among its prevention steps, and Cornell (for commercial growers) at least 7. In our reading, a 3- to 4-year cycle suits a home garden without clubroot.

Can brassicas take frost?

Most can. Oregon State lists kale, collards, cabbage, Brussels sprouts, broccoli, kohlrabi, turnips, rutabagas, radishes and arugula as taking heavy frost below 28 F; cauliflower takes only light frost, 28 to 32 F. That list is from Corvallis, Oregon. Penn State says most cole crops withstand a frost.

Why are there holes in my kale and cabbage leaves?

Many small round holes, under 1/8 inch, point to flea beetles (Minnesota); larger holes that keep growing, with green or brown droppings nearby, point to cabbage worms or loopers (Maryland). Row cover over young plants keeps both off.

What is clubroot?

A soil disease of the cabbage family that swells roots into galls and stunts the plant. It favors cold, wet, acid soil, spreads on infected transplants and soil, and its spores can last up to eighteen years (UMass), which is why rotation and clean transplants matter.