Gadenin日本語Get the appPlan backwards from cool weather at heading
Cabbage packs a firm head at daytime temperatures around 59F to 68F (15C to 20C) and does it badly above 77F (25C). Everything else in the calendar follows from that. Work out when your cool weather falls, count back the days to harvest for the type you are growing, 60 days for an early cabbage and up to 100 for a late storage one, and that is your planting date. Then count back another four to five weeks for the sowing date.
In most climates that gives you two workable crops rather than one: a spring planting that heads before summer heat arrives, and a late summer planting that heads as the weather cools. Trying to head a cabbage through the hottest part of the year is the commonest reason a crop disappoints, and no amount of feeding or watering compensates.
| Crop | Sow | Heads during |
|---|---|---|
| Spring crop | Late winter, under cover | Late spring, before the heat |
| Autumn crop | Midsummer | Autumn, as nights cool |
| Overwintering crop | Late summer | Late winter into early spring |
The five stages
A cabbage crop runs through five distinct stages, and each one has a single decision that matters more than everything else in it. Knowing which stage you are in tells you what to be looking at, and just as usefully what to leave alone.
The stage most gardeners get wrong is the fourth. Once the head starts to cup, the job changes completely: you stop feeding, you keep the water even, and you start checking firmness. Continuing to treat a heading cabbage the way you treated it during frame building is what produces a loose, open head.
| Stage | Duration | The one thing that matters |
|---|---|---|
| Raising seedlings | Four to five weeks | Full light from the day the seed leaves open |
| Planting and establishment | Two weeks | Firm planting and mesh on the same day |
| Building the frame | Four to six weeks | Feed and water hard, protect every outer leaf |
| Heading | Three to six weeks | Stop nitrogen, keep moisture even |
| Harvest | Two to four weeks | Cut when firm, before rain splits it |
Frame building: this is when you feed
From about two weeks after planting until the center starts to cup, the plant is producing the large outer leaves that will later be turned into a head. This is the only window in which feeding really pays. Give a balanced feed roughly every two to three weeks, applied in a ring six to eight inches (15 to 20 cm) out from the stem where the feeding roots actually are, and water it in.
Water matters as much as feed here. Cabbage has a shallow root plate and large leaves, so it runs short quickly in dry weather, and a plant checked by drought at this stage makes fewer and smaller leaves and therefore a smaller head. Mulch the bed once the plants are established and water thoroughly when the top two inches (5 cm) of soil are dry rather than sprinkling daily.
- Feed every two to three weeks A balanced granular feed in a ring around the plant, watered in. Keep it off the leaves and away from the stem.
- Water deeply, not often Push a finger into the soil. Dry at two inches (5 cm) means water thoroughly at the base. Light daily sprinkling keeps the roots at the surface.
- Weed while the ground is still open Get the bed clean before the leaves close over the soil. Once the plants meet in the row you cannot weed without breaking leaves.
- Protect every outer leaf Do not tidy up leaves that look tatty. Head weight comes directly from outer leaf area, and each one you remove costs you.
Heading: change what you are doing
When the inner leaves start cupping inwards, stop feeding nitrogen. From this point the plant should be packing the leaves it has, and more nitrogen simply produces new soft leaf that pushes the wrap open. Keep the water even and mulched, because the swings between dry and wet at this stage are what split heads.
Check the head every week with the flat of your hand and note when it first feels solid. In a hot spell put shade cloth over the row, as several degrees cooler makes a visible difference to how tightly the head packs. This is also when to keep the mesh sealed, because a caterpillar that gets in now bores straight into the head.
- Last feed before the center cups Once you can see the inner leaves curling in, that was your last nitrogen application of the season.
- Press-test weekly Press the top of the head with your palm every week and note when it stops giving. That is the start of your harvest window.
- Cut before heavy rain A solid head plus a downpour equals a split head. If rain is forecast and the head is firm, cut it.
End of season: clear the ground properly
When the last head is cut, lift the stumps and roots out of the ground rather than digging them in. Brassica stumps left in the soil over winter are where cabbage root fly pupae and clubroot spores carry through to the next crop, and a bed cleared properly is worth more than any treatment you can apply in spring.
Look at the roots as you pull them. Clean white roots mean the ground is fine to use again in rotation. Knobbly galls mean clubroot and that bed needs liming and a long break from every brassica, including radish and turnip. Then write the bed layout down for next season, because a rotation you keep in your head is a rotation you will break.
Record for each bed: the sowing date, the planting date, the date the head first cupped, the cut date and the weight. That handful of numbers is what turns next year's cabbage from a guess into a plan.