Gadenin日本語Get the appThe shape of the mizuna year
Mizuna is a cool season crop that grows best between about 40F and 70F (4C to 21C) and is very cold hardy: established plants shrug off frost and survive down to around 15F (minus 9C) unprotected, often lower under a cloche. Heat is the enemy, not cold. Above roughly 77F (25C) growth slows, the flavor sharpens, and the plant starts thinking about flowering.
That gives a year with two sowing windows either side of summer and one long harvest that stretches from autumn through winter. The autumn window is by far the more productive of the two, because the crop grows into improving conditions rather than towards heat.
Nothing below is tied to a calendar date. Work from soil temperature and from your own frost dates, and the same sequence applies in either hemisphere.
| Stage | Trigger | Main jobs |
|---|---|---|
| Late winter to early spring | Soil workable, above 40F (4C) | First sowings under cover or mesh; thin |
| Spring | Soil 50 to 60F (10 to 15C) | Main spring sowings; feed; watch flea beetles |
| Late spring | Days over 70F (21C) | Last spring sowing; harvest hard before bolting |
| Summer | Consistently over 77F (25C) | Rest the ground, or grow in shade only |
| Late summer | Heat breaking | Start the autumn sowings; this is the main crop |
| Autumn | Nights cooling | Successional sowings; feed; harvest steadily |
| Winter | Frosts arriving | Cloche or row cover; harvest through the cold |
The spring crop is a race against heat
Sow as soon as the soil is workable and above 40F (4C). Growth is slow at first but the plants establish while pests are still scarce, and a cloche or a layer of row cover over the row brings the first cut forward by two or three weeks. Keep sowing short rows every fortnight until daytime temperatures start reaching 70F (21C).
After that point every sowing is on borrowed time. Long days combined with warmth push the plants into flower, and a spring stand can go from perfect to bolted in under a week. The right response is to pick hard rather than to hope: cut everything usable while the leaves are still good and accept the end of the crop.
Note the date the spring sowings bolt each year. That date, not the packet, tells you when your last worthwhile spring sowing should go in.
The autumn and winter crop is the real one
Start sowing again as soon as the worst of the summer heat breaks, and keep going every two to three weeks until about eight weeks before your first hard frost. Plants from these sowings grow into cooling weather with shortening days, which suppresses flowering entirely, and the leaves stay tender and mild in a way spring plants rarely manage.
Frost improves them. Cold weather converts starches to sugars in the leaves, so mizuna picked after a hard frost is noticeably sweeter and less harsh than the same plant picked in autumn. A stand that has been frozen and thawed several times will look wretched at dawn and be perfectly fine by midday.
Growth effectively stops when day length drops below about ten hours, whatever the temperature. Plants hold rather than grow, and you are harvesting from what is already there. Plan for that by having the plants at full size before the light goes, not half-grown.
- Cover before the first hard frost A cloche, low tunnel or double layer of row cover takes the crop from surviving to producing. Under cover mizuna keeps making usable leaves through most of the winter in a mild region.
- Pick at midday in freezing weather Frozen leaves bruise and go to mush when handled. Wait until they have thawed in the sun before cutting, and they will be crisp.
- Stop feeding a month before hard frost Soft new growth going into a freeze is the growth that rots. Let the plants harden off and they take the cold far better.
Summer, and what to do with the gap
In most gardens there is a stretch of high summer where mizuna is simply not worth sowing. Seed germinates erratically above 85F (29C), flea beetles are at their peak, and anything that does come up bolts within weeks. Trying to force a crop through it wastes seed and gives you hot, stringy leaves.
If you want to try, give the row afternoon shade, sow into soil you have watered and cooled first, and pick everything as baby leaf within a month. Otherwise use the gap: clear the bed, add compost, and have it ready so the autumn sowings go in the day the weather turns.
A plant that has begun to bolt is not wasted. The flowering shoots are edible, sweeter than the mature leaves, and good raw or briefly cooked. Pick them before the buds open. Leave one plant to set seed and you will have more mizuna seed than you can use.
The records that make next year easier
Four dates per season are enough to plan properly the following year: the date of each sowing, the date of the first cut from it, the date the spring stand bolted, and the date the winter stand stopped regrowing. Add the position of each row and the spacing you used.
Those numbers turn general advice into your own calendar. You will know how many days from sowing to first cut in your soil at each time of year, exactly how late you can sow in autumn and still get a full-size plant before the light goes, and which bed keeps producing longest through the cold.