How to grow cabbage

The most common cabbage disappointment is a row of small hard heads, and it is almost always a spacing problem. A cabbage builds its head out of what its leaves capture, so a plant with more room makes a bigger head — the relationship is that direct, and it means spacing is not a rule to follow but a choice about what you want.

Our calendar gives cabbage fifteen inches in the row with twenty-four between, which produces a good household-sized head. The 1912 table, hand-cultivation column, gives twelve to eighteen inches in rows twenty-four to thirty inches apart — near enough the same answer, a century earlier. Solomon, growing without irrigation, separates early savoys by about thirty inches and gives the big late ones four feet, or sixteen square feet each.

If you want small heads for a small household, plant closer deliberately and harvest younger. What does not work is planting close by accident and hoping.

The other half of the spacing question is firmness. Brassicas want ground that has settled, not ground freshly forked into a fluffy tilth — a loose-planted cabbage rocks in the wind, chafes its stem, and sulks. Firm each transplant in hard enough that a tugged leaf tears rather than the plant lifting.

Cabbage is a heavy feeder and it occupies its ground for a long time, so the fertility has to be there before you plant. Compost or well-rotted manure dug in ahead of the crop, plus a nitrogen-leaning feed once the plants are away, is the whole regime.

Lime matters more than the feeding does. The cabbage family prefers soil near neutral, and acidic soil — the maritime Northwest's default — both weakens the crop and encourages clubroot, which is the one cabbage problem you genuinely cannot undo. A soil test is the single most useful thing to know about a brassica bed and it need only be done once every few years.

Water steadily rather than heavily. Cabbage is not especially thirsty, but it is very sensitive to the pattern: a plant that dries out, forms a firm head, and then gets a soaking will split, because the inside starts growing again and the outside cannot stretch. That is the mechanism behind almost every split cabbage.

A young cabbage is a small plant sitting in a large amount of open ground, and that open ground grows weeds faster than it grows cabbage. Weeds compete for exactly the nitrogen and moisture the crop needs during the weeks it is building the frame that will later build the head — so weeding early is not tidiness, it is yield.

The two photographs below are the same block a short time apart, and they make the case better than any argument. In the first, weed pressure is building between plants still too small to shade the ground. In the second the weeds have been cleared by hand and left lying between the rows, which is worth noticing: pulled weeds left on the surface in dry weather dry out, die, and return their moisture and nutrients to the bed rather than being carted away.

Once the plants are large enough for their leaves to close over the soil, they suppress weeds themselves and the job is largely done. Everything before that point is the work.

Cabbage white caterpillars are the visible problem: they shred leaves and then work into the head, where they are very difficult to get out. Fine insect mesh over hoops from the day of planting prevents the butterfly laying at all, and is far more effective than anything done afterwards. Where they get in, hand-picking works on a small planting and Bacillus thuringiensis on a large one.

Cabbage root fly maggots attack the stem base and can kill a young transplant outright. A collar of card or roofing felt laid flat on the soil around each stem stops the fly laying where it needs to, costs nothing, and is one of the highest-return five minutes in the vegetable garden.

Cabbage aphids form dense grey colonies in the growing point and between the outer leaves. Catch them early; once they are inside a forming head you have lost that plant.

Slugs take young transplants, particularly in a wet spring, and mostly stop being a problem once the plant has half a dozen leaves.

And clubroot, which is in a category of its own because it is permanent. It distorts the roots, wilts the plant in sun, and once in a bed it stays for many years. There is no cure. The management is liming towards neutral, the longest rotation you can manage, raising plants in large pots so they go out big enough to outrun early infection, and — most importantly — never importing soil or brassica transplants from an infected garden.

Cut when the head feels solid to a firm squeeze. A head left past that point in wet or fast-growing weather will split, and a split head does not store and rots quickly in the field.

If you can see splitting coming — a firm head, and rain forecast after a dry spell — you can buy time by breaking some of the roots. Take hold of the plant and give it a sharp quarter-turn, or push a spade down on one side. It sounds brutal and it works: less water reaches the head, and growth slows enough to hold it for another week or two.

The trick most gardeners never learn: leave the stump in the ground. Cut the head off cleanly, leave the stalk and its outer leaves, and score a shallow cross in the top of the cut stump. Within a few weeks it will push out a cluster of small secondary heads — not a second full cabbage, but a genuinely useful crop of loose greens from a plant you had finished with.

For storage, cut with a few outer leaves left on, keep it cold and humid, and check regularly. Dense winter varieties and red cabbages keep for months in the right conditions; loose summer types keep for days.