Gadenin日本語Get the appSow in late summer so the plants meet winter half grown
Flowering brassica shoots are grown for the flower stem itself, picked while the buds are still shut. That reverses the whole logic of every other leafy brassica you grow, where a flower stem means the crop has failed. Here the flower stem is the crop, and the sowing date exists to line the plant up so it runs to bud in late winter and early spring rather than in the middle of summer heat.
The main sowing goes in from the point where the worst summer heat breaks until about ten weeks before your first hard frost. That gives the plant enough warm weeks to build a fist-sized rosette and a real root system, and then the cold arrives and holds it there. A plant that goes into winter at that size will push its first shoot as soon as days lengthen. A plant sown four weeks late goes into winter as a thumb-sized seedling, sits all winter doing nothing visible, and produces a thin, short-lived flush a month behind everyone else's.
Seed germinates from about 45F to 85F (7C to 29C) and comes up in four to seven days at 60F (15C). Late-summer soil is usually warmer than that, so expect three or four days and be ready with water. Sow a quarter to a half inch (5 to 12 mm) deep. Deeper than that and the seedlings emerge weak and stretched, which matters because a stretched seedling makes a floppy crown that catches water and rots over winter.
| Soil temperature | Days to emerge | What to expect |
|---|---|---|
| 45F (7C) | 10 to 14 | Slow and uneven; only worth it for a spring sowing |
| 55F (13C) | 6 to 8 | Even stands, stocky seedlings |
| 65F (18C) | 4 to 5 | The usual late-summer case; best balance |
| 80F (27C) | 3 | Fast but leggy; shade the drill and water twice a day |
| Above 85F (29C) | Erratic | Patchy germination and flea beetle damage; wait a week |
Spacing decides how many side shoots you get
Every plant gives you one main shoot and then, after that shoot is cut, a run of side shoots from the leaf joints below the cut. The number of side shoots depends almost entirely on how many leaf joints the plant built before it ran to bud, and that depends on spacing. A crowded plant makes a narrow stem with five or six usable joints. A plant with room makes a stocky stem with twelve or more, and keeps cutting for three or four weeks longer.
Give each plant ten to fifteen inches (25 to 38 cm) each way for the main crop. That looks absurdly generous in autumn when the plants are the size of a hand, and correct in late winter when they have doubled. Rows eighteen inches (45 cm) apart give you somewhere to walk during the harvest, which matters more than it sounds, because you will be in this bed every two or three days for over a month.
There is a second, entirely different way to grow it: sow thickly in a band, do not thin, and take a single tender shoot from each crowded plant as a one-off cut. That gives a fast, dense crop from a small area but no second flush. Decide which you want before the seed goes in, because you cannot convert one into the other later.
| Growing style | Final spacing | Shoots per plant | Harvest window |
|---|---|---|---|
| Main crop, overwintered | 10 to 15 in (25 to 38 cm) | Main shoot plus 10 to 15 sides | Four to seven weeks |
| Close spaced | 6 in (15 cm) | Main shoot plus 4 to 6 sides | Two to three weeks |
| Dense band, no thinning | 2 in (5 cm) | One shoot only | One cut, then clear |
Direct sowing versus modules
Direct sowing works and gives the strongest taproot, which is worth having for a plant that has to stand through a winter. Sow three seeds every ten inches (25 cm) along the drill and thin to the best one at the first true leaf. Thin by snipping at soil level rather than pulling, because the roots knit together at that stage and pulling one lifts its neighbors.
Modules are the better choice if your late-summer beds are still full of the previous crop, which is usually the case. Sow two seeds per cell in a small module, thin to one, and plant out at four true leaves, which takes about three weeks. Do not let a module plant sit past five true leaves. Root-bound brassica transplants make a permanently stunted crown and never build the leaf joints that the side shoots come from.
Whichever route you take, firm the soil around the transplant hard with your knuckles. A plant that rocks in winter wind opens a funnel around its stem, water collects in it, and the crown rots at exactly the point where all your side shoots were going to come from.
If flea beetles are shredding your seedlings, cover the bed with fine insect mesh from the day you sow until the plants have six true leaves. After that the leaves are tough enough that the damage is cosmetic and you can take the mesh off.
Write down the sowing date and the plant positions
The single most useful record for this crop is the gap between sowing date and the day you cut the first main shoot. It is usually somewhere between twenty and thirty weeks for an autumn sowing, and it is remarkably consistent in a given garden. Once you have two seasons of it, you can shift the sowing date by a fortnight and know exactly where the harvest will land.
Also note where each plant stood and how many shoots it gave. Plants at the end of a row, or against a wall, routinely out-produce the ones in the middle by a wide margin, and after one season you will know whether that is wind, drainage or warmth in your particular plot. Record the date the first bud cluster becomes visible in the crown as well, because that is the signal to start feeding and to start checking the bed every other day.