Gadenin日本語Get the appFast growth is the whole strategy
Kailan is eaten as a stem, and stem quality is entirely a function of growth rate. A plant that grows without a check from sowing to cutting gives a stem that snaps cleanly and cooks tender. A plant that stalls, from drought, from cold, from starvation, or from a root disturbance, lays down fiber in the stem while it waits, and that fiber never softens again. You cannot rescue a woody stem with better treatment later.
Every decision therefore comes down to one question: does this keep the plant moving, or does it stop it for a few days? Water before the plant wilts rather than after. Feed before the leaves pale rather than after. Weed while the weeds are small rather than pulling large ones out from between the roots.
Water deeply twice a week, not a splash every day
Kailan has a shallow, wide root system, and it responds badly to the wet and dry swings that a daily sprinkle creates. Give it a good soak that wets the top 6 to 8 inches (15 to 20 cm) of soil twice a week, and more often in hot weather or on sand. That is roughly an inch (25 mm) of water a week, and up to an inch and a half (38 mm) once the stems are extending.
The critical period is the two to three weeks when the stem is elongating and the bud head is forming. Drought at that point produces a hollow, pithy center in an otherwise decent stem.
Check by pushing a finger into the soil next to a plant. If it is dry at two inches (5 cm), water. Watering by the calendar rather than by the soil is why crops get overwatered in a wet season and underwatered in a dry one.
- Water the soil, not the leaves Aim the can or hose at the base of each plant. Wet foliage in warm still weather is an invitation to downy mildew, and water sitting in the crown of leaves does nothing for the roots.
- Mulch once the plants are 4 inches (10 cm) tall An inch (2.5 cm) of compost or grass clippings around the plants halves the watering frequency, keeps the soil cool in heat, and suppresses the weeds that would otherwise compete at exactly the wrong time.
- Water in the morning Morning watering means the plant has a full reservoir going into the heat of the day and the surface dries before nightfall, which keeps slug damage down.
Wilting at midday in strong sun is normal and not a signal to water. Wilting first thing in the morning is a real drought signal and needs a soak the same day.
One nitrogen feed does most of the work
Kailan is a leaf and stem crop, so nitrogen is what it wants, and there is no head to spoil by pushing it. Work in well rotted compost or manure before sowing at a bucketful per square yard (square meter), then give a single nitrogen top dressing about three weeks after thinning, when the plants have six to eight true leaves and are starting to stand up.
A high nitrogen liquid feed, a diluted comfrey brew, or a light scatter of granular fertilizer raked into the surface all do the job. Apply along the row six inches (15 cm) from the stems and water it in; fertilizer touching the stem base scorches it.
After the first cut, feed again. The side shoot flush is a second crop and it draws on the same reserves. A plant that is cut and then left unfed produces two or three thin shoots and gives up; a plant that is cut and fed produces shoots for weeks.
| Stage | What to give | Why |
|---|---|---|
| Before sowing | Compost or rotted manure, a bucket per square yard (square meter) | Holds water and releases nitrogen slowly through the crop |
| Three weeks after final thin | High nitrogen liquid feed or a light granular top dressing | Drives leaf area, which is what builds a thick stem |
| As buds first appear | Nothing new, just keep water steady | The stem is elongating and needs water more than feed |
| Straight after the first cut | High nitrogen liquid feed | Fuels the side shoots that follow the main stem |
| Every two to three weeks while cutting shoots | Half strength liquid feed | Keeps the shoot flush going instead of petering out |
Read the plant rather than the schedule
Kailan tells you what it is short of quite clearly, and the signals are worth learning because the crop moves fast enough that a fortnight of the wrong treatment costs you the whole planting. Look at the oldest leaves first, since a plant short of nitrogen strips it out of the old leaves to build new ones.
Note that purple tinting on a kailan stem in cold weather is normal and is not a phosphorus problem. It is the same pigment response that colors many brassicas in a cold snap and it disappears when the weather warms.
| What you see | Most likely cause | What to do |
|---|---|---|
| Oldest leaves pale, whole plant light green | Nitrogen shortage | Liquid feed now and again in ten days |
| Leaves small, plant short and hard, stem thin | Crowding or drought earlier in the crop | Too late to fix; cut as baby stems and sow again wider |
| Wilting in the morning | Real water shortage | Soak to 8 inches (20 cm) and mulch |
| Yellow blotches on top of the leaf, gray felt beneath | Downy mildew from wet foliage | Improve airflow, water at the base only, remove worst leaves |
| Purple flush on stems in cold weather | Normal cold response | Nothing; it fades as temperatures rise |
| Fast lush growth then a floppy, soft stem | Too much nitrogen too late | Stop feeding, keep water even, cut slightly earlier |
Heat and cold: this brassica handles both
Kailan is the most heat tolerant of the common brassicas and will keep producing usable stems at 85F (29C) when broccoli and cauliflower have long since bolted into uselessness. That does not mean heat is free. Above about 85F (29C) the stems come thinner, the flavor turns sharper, and the plants run to open flower faster, so the cutting window narrows from a few days to about two.
In summer, the two things that keep the crop honest are shade and water. Light shade over the middle of the day, from a shade cloth or from the shadow of a taller crop, keeps the stems tender, and so does deep mulch, which holds root temperature down more effectively than shading the leaves does. At the other end, mature kailan takes a light frost without complaint and the flavor sweetens noticeably after a cold night. Young seedlings are more vulnerable, and repeated cold below 50F (10C) at the seedling stage will make some plants flower prematurely on a short stem. Row cover the early sowings rather than gambling on a mild spell.
- Shade the bed above 85F (29C) Rig 30 percent shade cloth a foot (30 cm) above the plants for the middle of the day. It is worth more than any amount of extra watering once the air is that hot.
- Row cover seedlings through cold snaps Cover early sowings when nights drop under 50F (10C). Cold at the seedling stage is stored up and paid back later as premature flowering on short stems.
- Leave the last sowing out through the first frosts A mature plant takes light frost and eats better for it. Cut only after the stems have thawed in the morning, since frozen stems bruise when handled.
Keep a note of the feed dates and the weather
Write down the date of each feed, the date of the first cut, and the run of daytime temperatures in the fortnight before that cut. Kailan is fast enough that the link between a hot spell and a thin stem, or between a missed feed and a short side shoot flush, is visible within a single season rather than needing years of records.
The most valuable note is the one you make when something goes wrong. A row that gave woody stems is worth a line saying what happened to it: a week of missed watering, a late thinning, a cold snap at two leaves. Next year that line tells you which of your habits to change instead of leaving you guessing.