Gadenin日本語Get the appThe crop runs in weeks, so think in successions
From sowing to a full-size plant is thirty to fifty days depending on temperature, and a salad cutting is ready in three weeks. Nothing about this crop is planned a season ahead. The useful unit is a small sowing every two to three weeks, each one a fraction of a bed, so that something is always at cutting size and nothing stands past its best.
The other consequence of the speed is that it fits into gaps. Komatsuna will occupy a bed between two slower crops, fill the space between rows of something that has not yet closed over, or take over a container as soon as a summer crop is pulled out. It is worth keeping seed permanently to hand for that reason.
The only real constraint is that it is a brassica, so it must not follow another brassica in the same ground. When you are slotting quick sowings into gaps this is easy to forget, and clubroot is the punishment.
Season by season
The table works from soil and air conditions rather than months so it reads the same in either hemisphere. The autumn sowing is the one to prioritize if you only make one: growth is steady, pests are declining, bolting is not a risk, and frost improves the flavor.
| Season | Conditions to sow into | Time to harvest | What to watch |
|---|---|---|---|
| Early spring | Soil above 50F (10C), under cloche or row cover | 6 to 8 weeks | Slugs; slow patchy germination in cold soil |
| Late spring | Soil 59 to 68F (15 to 20C) | 4 to 5 weeks | Flea beetle arriving; lengthening days push bolting |
| Summer | Shaded ground, sown late in the day | 3 to 4 weeks | Heat, caterpillars, bolting; grow for baby leaf only |
| Early autumn | Soil 59 to 72F (15 to 22C), cooling | 5 to 6 weeks | The best sowing of the year; cover against late caterpillars |
| Late autumn | Soil above 50F (10C), under cover | 8 to 10 weeks | Slow steady growth; frost sweetens the leaf |
| Winter | Under a cloche, tunnel or cold frame only | 10 weeks or more | Almost no growth in the shortest weeks; keep it dry-ish |
Komatsuna survives frost down to around 15F (minus 9C) under a cloche and shrugs off light frost unprotected. A standing crop through the cold months is a genuine option, not an experiment.
Running a succession without a spreadsheet
The mechanism that works is simple and needs no planning further ahead than the next fortnight. It relies on sowing small, which is the part most people get wrong.
- Sow a strip, not a bed A row three feet (1 m) long, or one pot. That is more komatsuna than it sounds, and a small sowing is one you will actually eat before it goes over.
- Sow the next one when the last one germinates Use emergence as the trigger rather than a date. That naturally stretches the interval in cold weather, when everything is slower, and shortens it in warm weather, which is exactly what you want.
- Stop the spring successions when the days get long and hot Sowings made into rising heat and long days bolt before they size up. Skip the hottest weeks for full-size plants and sow only shaded baby leaf, then restart properly as the nights begin to cool.
- Make the biggest sowing as the season turns cool This is the crop that will stand. Sow enough to pick from for two months, thin it wide to six inches (15 cm), and put a cloche or row cover over it before the first hard frost.
- Move each sowing to different ground Keep a rough map of where the brassicas have been. With sowings this frequent it is easy to end up planting komatsuna after komatsuna in the same square foot without noticing.
What changes as the days lengthen
Komatsuna runs to flower under a combination of lengthening days and warmth, and it is markedly slower to do so than most of the leafy brassicas, which is its main virtue. It will still bolt eventually. The signal is the center of the plant elongating and the new leaves coming out narrow and pointed instead of broad and rounded.
A plant that has been checked, by drying out, by root damage during thinning, or by a spell of cold after a warm start, bolts sooner than one that has grown steadily. This is why the fast even growth that comes from adequate water and proper spacing is not just about size; it is what keeps the crop in leaf.
Once a plant has begun to flower there is no reversing it. Take the flowering shoots while the buds are tight and eat them, then clear the row. Do not leave a bolted brassica standing in the bed unless you deliberately want the seed, because it becomes an aphid nursery.
The four things worth writing down
Keep a simple record and after one full year you will stop guessing. Note the sowing date and which bed or pot it went into, because that is your rotation record. Note the emergence date, because the gap between sowing and emergence tells you how cold the soil really was. Note the date of the first cut, which gives you the true days-to-harvest for your garden in that season. And note the first date you saw each pest, along with whether the row was covered.
Add one line about how the crop turned out, in ordinary words: bolted early, went tough, best row of the year. Those notes are what let you decide next season whether to move a sowing earlier or later, and they are far more reliable than any general schedule because they are measured in your own soil, your own light and your own weather.