Gadenin日本語Get the appAutumn: build leaf, not flower
From planting until the cold sets in, your only job is to grow as large and stocky a rosette as possible. Every leaf the plant makes in autumn becomes a leaf joint, and every leaf joint is a potential side shoot in spring. A plant that goes into winter with sixteen leaves will out-yield one with eight by far more than double, because the extra leaves are also the fuel supply for the whole harvest.
Feed for that with nitrogen, and be generous about it in autumn only. A balanced feed at planting plus one nitrogen-leaning liquid feed three weeks later is about right on decent ground. On thin or sandy soil, feed every two weeks until growth slows with the cold. The signal that you have enough is leaves that are dark green and held up firmly rather than pale and lax.
Stop the nitrogen once night temperatures are consistently below about 45F (7C). Soft, sappy growth going into hard frost is the main cause of winter losses in this crop. From that point the plant should be firm, slightly leathery and a little bluish, which is exactly how a well-hardened brassica should look.
Winter: protect the crown, not the leaves
These plants take real cold. Established plants shrug off temperatures well below freezing, and a hard frost that flattens the outer leaves is not a problem as long as the growing point in the center of the rosette survives. Judge your winter protection by what is happening at the crown, not by how ragged the outer leaves look.
Two things kill overwintered plants, and neither is cold on its own. The first is waterlogging: roots sitting in cold, airless mud rot, and the plant collapses on the first mild day. If your ground holds water, plant on a low ridge four inches (10 cm) high or grow in raised beds. The second is wind rock, which opens a gap around the stem. Walk the bed after every gale and firm any plant that has loosened.
A row cover or low tunnel is worth using where winters are severe, but leave the ends open on mild days. Sealed covers over wet winter foliage breed gray mold in the crowns faster than the cold would have damaged them. Pull off any leaf that has gone slimy and yellow, both to keep air moving and because those leaves are where slugs shelter.
| Winter symptom | Likely cause | What to do |
|---|---|---|
| Outer leaves limp and bleached after frost | Normal frost damage | Nothing; they will be shed |
| Whole plant flat and gray in mild weather | Root rot from waterlogging | Pull it; improve drainage before next season |
| Plant leaning, gap around stem | Wind rock | Firm the soil back with your heel |
| Slimy brown patches in the crown | Gray mold under a sealed cover | Ventilate; strip the affected leaves |
| Leaves nibbled to lace overnight | Slugs under leaf litter | Clear the litter and check at night |
The turn: feed the moment buds show
As days lengthen, the plant stops making leaves and starts to lift a stem out of the center of the rosette. You will see the change a week or two before the buds are obvious: the newest leaves stand more upright and the center of the plant looks crowded. That is the moment to feed, and it is the highest-value feed of the whole season.
Give a liquid feed with real nitrogen in it, then repeat every ten to fourteen days for as long as you are harvesting. Every cut you make asks the plant to build another shoot out of a leaf joint, and unfed plants simply run out of material: the fourth and fifth rounds of side shoots come thin, short and quick to open. Fed plants keep producing shoots of usable thickness for weeks longer.
Water matters just as much once shoots are moving. Buds are mostly water and the plant is growing fast in still-cool soil, so a dry fortnight in early spring shows up directly as thin shoots and buds that open early. An inch (25 mm) of water a week, from rain or from you, is the target. Mulch after the first feed to hold it.
- Watch for the crowded center The newest leaves stand up rather than out and the middle of the rosette looks congested. This is a week or two ahead of visible buds and is your cue that the plant has switched from leaf to flower.
- Feed as soon as you see it A nitrogen-leaning liquid feed at the recommended strength, watered onto damp soil around the plant rather than over the crown. Repeat every ten to fourteen days throughout the harvest.
- Mulch and keep the water even One to two inches (2.5 to 5 cm) of compost around each plant once the soil has warmed a little. Aim for an inch (25 mm) of water a week. Uneven water is the main cause of thin, quick-opening shoots.
- Clear the old outer leaves Strip yellowing lower leaves as the stem lifts. They contribute nothing by then, they hide slugs and aphids, and removing them makes the leaf joints visible so you can see where the next shoots will come from.
Keep a note of what carried the crop
Record the date you gave the first spring feed and the date the shoots visibly thinned out. In most gardens the gap is four to six weeks, and if yours is much shorter, the answer is nearly always feeding rather than variety or weather. Note your watering too, at least roughly, because the correlation between a dry fortnight and a sudden drop in shoot quality is easy to see once it is written down and impossible to remember otherwise.
It is also worth logging how each plant came through the winter: which ones rotted, where they stood, and what the ground was like there. Winter losses cluster in the same few square feet year after year, and the fix is drainage rather than luck.