Pinching Perilla Grown for Seed: What to Cut and What to Leave

Every pinch buys you spikes, so start at four pairs of leaves

Perilla carries one flower spike on the end of every shoot. A plant with four shoots gives you four spikes; a plant with twenty-four shoots gives you twenty-four. Pinching is not cosmetic here, it is the whole yield calculation, and it is the single most useful thing you do to the plant all season.

Make the first pinch when the plant has four pairs of true leaves, usually at six to eight inches (15 to 20 cm) tall. Take out the growing tip just above the second or third pair, using your fingernails or snips. Within ten days each of the leaf joints below the cut pushes out a side shoot, and where you had one tip you now have four or six.

1. Count the pairs, not the height A plant stretched on a windowsill may be tall at two pairs of leaves and is not ready. Wait until four pairs have fully opened, so there are at least two good joints left below your cut to break into shoots.
2. Cut just above a leaf pair Leave a quarter of an inch (5 mm) of stem above the joint. A long stub above the leaves dies back and can rot down into the joint in wet weather; a cut flush against the leaves damages the buds you are trying to release.
3. Feed lightly a few days later A balanced liquid feed once the side shoots are visible pushes them away fast. Do not pour on high-nitrogen feed at this stage, or you get soft, sappy shoots that lodge as soon as the spikes fill.

Do not pinch in the first week after transplanting. The plant needs to get roots moving before it can push new shoots, and a pinch made on a wilting transplant just sits there for a fortnight.

Two or three rounds, then stop

Repeat the pinch on each new shoot when it has made three to four pairs of its own leaves, roughly every two to three weeks. Two rounds is enough for most gardens; a third is worth it on a plant that was sown early and has time in hand.

The rounds have diminishing returns, and there is a hard deadline. Every pinch delays the shoot behind it by ten to fourteen days, and a shoot that is still short and soft when daylength trips the plant produces a stunted spike or none at all. Stop pinching six weeks before your normal flowering time, which is to say around midsummer for most gardens.

The pinched tips are usable. They are the tenderest growth on the plant and worth keeping rather than dropping on the path, but that is a side benefit and not a reason to keep pinching past the cut-off.

Once the spikes appear, leave them alone

This is where a seed crop and a leaf crop part company completely. A gardener growing perilla for leaves pinches out every flower spike the moment it shows, because flowering turns the leaves small, tough and bitter, and the plant stops making new ones. All of that is still true here, and none of it matters, because the spike is the crop.

From late summer, when you see a tight green cluster forming at the end of a shoot, that is a spike starting. Leave it. Leave the ones below it. Resist the habit of tidying, because every spike you snap off in passing is one you will not pick, and unlike a leaf the plant will not make another in its place.

What you can still remove at this stage is anything below the spikes that is doing nothing: yellowing lower leaves, a shoot that has been shaded out and stayed thin, or a branch broken by wind. Taking those out moves air through the plant while the seed ripens, which matters more in a damp autumn than it does earlier in the year.

1. Stop tidying the tops Put the snips down as soon as the first spike shows. If you need to shape the plant, do it below the level where spikes are forming, never at the tips.
2. Strip yellow lower leaves Pull off any leaf in the bottom quarter of the plant that has gone yellow or is lying on wet soil. It contributes nothing at this stage and is where leaf spot starts.
3. Stake before the heads fill A well-pinched plant is wide and gets heavy. Put a cane in on each side and run a loop of string round the plant while the spikes are still light, not after the first storm has flattened it.

Record the date you saw the first spike each year. It varies very little from one season to the next in the same garden, and once you have two years of it you know exactly when to stop pinching and when to start checking the heads.

Rescuing a plant you never pinched

An unpinched perilla grows as a single upright stem with short side branches near the top, and it will give you one good terminal spike and a handful of small ones. If you catch it before midsummer there is still time to fix it, and the fix is drastic: cut the main stem back by a third to a half, to just above a strong pair of leaves.

It looks like vandalism and the plant sulks for a week, but it breaks from every joint below the cut and rebuilds as a bush. What you cannot do is leave it and hope. A single stem that reaches flowering unpinched is finished as a seed crop, and the only remedy left is to sow earlier next year.