Caring for Perilla Grown for Seed: Water, Feed and Support

Water steadily, then ease off as the seed fills

Perilla has shallow roots and large thin leaves, and it wilts dramatically on a hot afternoon. Through spring and early summer, while you are building the branch framework, keep the soil evenly damp: a deep soak every two to three days in the ground, daily in a container once the plant fills its pot. A plant that is repeatedly allowed to wilt hard makes short internodes and fewer usable shoots.

The pattern changes once the spikes form. From flowering onward reduce watering to roughly half, enough that the plant does not wilt but not enough to keep the head of the plant permanently damp. Wet spikes in a still, humid autumn go moldy, and mold in a ripening head cannot be undone.

Judge by the soil rather than the calendar. Push a finger in to the second knuckle; if it comes out damp, wait. Afternoon wilting on a hot day when the soil below the surface is still wet is heat stress, not thirst, and watering into that is how you end up with root problems.

Feed early, taper before flowering

Nitrogen builds leaves and shoots, which is exactly what you want in the first half of the season. Work a general-purpose granular feed into the bed before planting, then give a balanced liquid feed every two to three weeks while you are pinching. In a container the same feed goes on weekly at half strength, because you are watering the nutrients straight out of the bottom.

Stop the nitrogen once you have made the last pinch. A plant still being pushed with high-nitrogen feed at flowering makes soft, dark, floppy growth, sets seed poorly, and is far more attractive to aphids. If you feed at all from that point, switch to something low in nitrogen and higher in potassium, at half rate, no more than twice.

Perilla is not a hungry crop and it is easy to overdo. If the leaves are deep green, the stems are thick and soft, and the plant is putting on height without branching, you are feeding too much. Stop, water plainly for a fortnight, and it will settle.

Do not feed a dry plant. Water first, feed into damp soil an hour later. Liquid feed on dry roots scorches the fine root hairs and the plant checks for a week.

Support the plant before it needs it

This is the step most people skip and regret. A perilla pinched twice is a broad, top-heavy bush, and once twenty or thirty spikes fill with seed the whole plant becomes a sail. The first autumn gale lays it flat on wet ground, where the heads pick up soil, mold, and slugs within days. Flattened spikes rarely ripen usable seed.

Put the support in while the spikes are still forming and light. Two canes either side of the plant with a loop of soft string at about two-thirds of the plant's height is enough for a single plant. For a row, run canes at each end and every four feet (1.2 m) along, with two lines of string on each side of the row at eighteen inches (45 cm) and thirty inches (75 cm).

Standing a flattened plant back up afterwards is only half a rescue. The stem cracks at the base when it goes over, and even tied up again the plant never moves water properly to the heads. Ten minutes with canes in late summer is worth more than any amount of tidying afterwards.

1. Get canes in before flowering Push them in while the roots are still small enough not to mind. Driving a cane through the root plate of a mature plant does real damage at exactly the wrong moment.
2. Use soft, wide ties String or fabric tape, never wire or a thin cable tie. Perilla stems are hollow-ish and square, and a thin tie cuts straight into them as the stem swells.
3. Check ties after every storm Look at where the string crosses the stem. A tie that has bitten in leaves a constriction, and everything above it ripens badly.

What to write down while the plant is growing

A seed crop is judged on timing more than on anything else, and timing repeats closely from year to year in the same garden. Keeping a handful of dates turns next season from guesswork into a schedule you can follow, and it takes under a minute each time.

The dates worth having are: when you sowed, when you set the plants out, each pinch, the day you first saw a flower spike, the day the lowest flowers on a spike opened, and the day the first seed felt hard between finger and thumb. The gap between the last three is usually two to three weeks in total, and knowing it is the difference between picking spikes at the right stage and finding them a week past.

Alongside the dates, note the position of each plant and where any self-sown seedlings came up. The position matters because you will want to know which plant shattered before you cut it, and because perilla should not be grown in the same spot year after year while its own volunteers are coming up around it.