Of all the cool-season vegetables, few are as variable and satisfying to grow as cole crops (Brassica oleracea), also called “brassicas”. Tasty favorites like kale, cabbage, broccoli, and cauliflower yield big harvests and are easily grown the organic way, even in the face of lots of pests. It all starts with healthy plants and good care.
Where summers are hot, cole crops are best grown in spring or fall, but in my community garden my spring crops yield better. This is largely due to plentiful foragers, like rabbits, groundhogs, voles, and deer. By summer’s end, mammalian garden pests are in larger numbers and always take a toll on my fall crops—particularly my brassicas. Fencing and smelly organic animal repellants like 100% natural Plantskydd will help, but it’s always a battle.
In spring, it pays to plant large, robust seedling starts for quick establishment and good success. If growing from seed, I begin planting early indoors—generally in late February to early March. By the time my plantlets are 4-inches tall, they are ready to harden off and plant outdoors. Starts are also sold at local nurseries, though they offer less selection. Seed catalogs always have newer, more interesting varieties. This year I chose seeds for the small-headed savoy cabbage ‘Alcosa’, broad-leaved ‘Galega de Folhas Lisas’ kale, bolt-resistant ‘Packman’ broccoli, and bright purple ‘Graffiti’ cauliflower.
Brassicas require full sun for best growth. Deep, fertile soil with a slightly acid to neutral pH (6-7) is ideal. Be sure to amend the soil with Fafard® Sphagnum Peat Moss and Premium Natural & Organic Compost —being sure to till amendments in deeply—and fortify with a fertilizer formulated for vegetables. These vegetables have high macronutrient requirements (NPK 14-14-14) and specific micronutrient needs (high calcium and boron). At planting time, I recommend fertilizing with an OMRI-Listed (certified by the Organic Materials Review Institute) vegetable fertilizer, bone meal, and borax, at the recommended doses.
Set plants out after hard frosts have ended but cool days and light frosts are still expected. Most cole crops can withstand freezing temperatures down to 20° F but grow best at temperatures between 70° and 85° F. Late March to early April is the best planting window where I live in the Mid-Atlantic.
Each brassica grows a little differently and may require slightly different care. Here are the growing basics for my spring standbys:
Broccoli varieties vary widely. Some produce enormous central clusters and others smaller clusters with ample side shoots; some have large, loose beads (buds) while others have small beads produced in tight, dense clusters. Gardeners can expect plants to bear heads 50 to 70 days after planting. ‘Packman’, ‘Diplomat’, and ‘Early Purple’ are three high-performing varieties that produce big heads, have good side shoot production, and grow beautifully in spring.
Broccoli seedlings look like nondescript leafy sprouts, but in a matter of months they will produce big budding heads of broccoli. Space your broccoli plants about 1 to 1.5 feet apart at planting time, and plant a minimum of six plants for good yields. Don’t allow newly planted seedlings to dry out, and ensure established plants always get ample water. Once nice broccoli heads are set, harvest them and wait for more to develop. Broccoli is a cut-and-come-again crop that should not be allowed to flower and set seed. I generally harvest mine with garden shears or a garden knife.
There are a couple of troubles specific to broccoli. Boron deficiency causes florets to turn brown prematurely and stems to become hollow. Additionally, insufficient water will keep plants from setting florets, and heat in excess of 86 ° F may encourage plants to bolt quickly and taste bitter.
There are lots of fun cabbage varieties offering different flavors, looks and characteristics. Heads may be conical, flattened, rounded, large or small, and can have smooth or savoyed leaves. Four varieties for connoisseurs are the blue-green and purple-pink blushed ‘San Michele’, dwarf conical ‘Caraflex’, giant sweet savoyed ‘Drumhead’, and elongated purple ‘Kalibos.’ Days to harvest vary from variety to variety , but on average you can expect heads to develop 63 to 88 days after planting.
Seedlings should be planted outside when they are around 4 to 6 inches tall. Compact varieties may be spaced as close as 10 inches apart and large varieties between 18 and 24 inches apart. Once healthy heads develop, cut them at the base with a garden knife and remove any large, ratty lower leaves. Cabbage will store for a long time, if refrigerated or kept in a cool dry place.
There are several common cabbage nutrient deficiencies. Potassium deficiency is common and results in heads with leaves that become yellow then dry and papery along the edges. If comparable yellowing is seen between the leaves, then magnesium deficiency is likely the problem. Heads with weak or hollow stems are suffering from boron deficiency.
Cauliflower comes in a myriad of sizes (tiny to giant) and colors (white, green, purple and orange). Fun, interesting varieties include the dwarf heirloom ‘Snowball’, bright purple ‘Graffiti’, electric orange ‘Cheddar’, and very large ‘Giant Naples.’
The sooner you can get your cauliflower into spring ground, the bigger the heads will be, but it’s important to note that this brassica is not as frost-tolerant as cabbages, broccoli and kale. Seedlings should be planted 18 to 20 inches apart. Be sure to give plants ample water when cauliflower heads begin to develop. Layers of leaves cover and protect developing heads from sun and pests. Once the leaves unfurl and heads look curdy and fully developed, they can be cut from beneath and harvested.
Nutrient deficiencies and heat troubles that plague broccoli are also a problem with cauliflower. Excessive heat and ill-timed harvest can cause heads to elongate and taste bitter.
Some of the best kale varieties for eating are the popular ‘Nero di Toscana’ (aka. dinosaur kale), heat-tolerant Portuguese ‘Tronchuda Beira’, and frilly, tender ‘Red Ursa’. Young leaves can be eaten fresh in salads and more mature leaves are great for cooking.
Kales are cold hardy and can be planted along with broccoli and cabbage starts. Spacing varies from variety to variety, but on average 12 to 18 inches apart is a good planting range. Leaves can be harvested as soon as plants reach a reasonable size and have ample foliage. Harvest leaves as needed using clean shears.
Unlike the other cole crops mentioned, kales can survive hot summers with care. Be sure to water them well through the hot months while protecting them from summer pests, namely harlequin bugs and cabbage loopers.
Lots of pests predate on brassicas. Slugs and cabbage loopers (Trichoplusia ni) commonly attack cabbage heads, eating their way through the layers of leaves. Harlequin bugs (Murgantia histrionica) are aggressive sucking insects known to lay waste to summer kales, and cabbage maggots (Delia radicum) will de-root and gut spring plants in no time.
There are several organic methods to tackling these pests. Sluggo® is a non-toxic, OMRI-Listed pesticide that will quickly take care of slugs. Cabbage loopers are best tackled with a product containing BT (Bacillus thuringiensis); OMRI-Listed Safer® Caterpillar Killer is a great choice. Harlequin beetles are eradicated at all stages with products containing neem oil, a popular organic pesticide, and applying a sprinkling of wood ashes around the base your brassicas will deter cabbage root maggots.
It also pays to recognize and destroy the pest eggs on sight: Small, pearly cabbage looper eggs are laid singly or in small, open clusters (5-7 eggs) on leaf surfaces; harlequin bug eggs look like black and white bulls-eyed barrels laid in tight clusters (~12 eggs) along leaf undersides; cabbage maggot flies lay eggs near the base of plants, so it can be helpful to sink 3” plastic bottle collars (1” below ground, 2” above) to keep hatched maggots from reaching seedlings.
With good care, any gardener can grow broccoli, cabbage, cauliflower and kale organically. Once the harvest begins, it will make all the work worth it.