Perilla (Shiso)

Sow or set out shiso once frost has passed

Shiso can be direct seeded in the garden or set out as transplants in spring. Give it full sun to partial shade and allow about 2 feet per plant, since a single plant fills out to roughly 2 to 3 feet tall and wants the room. Shiso is a frost-tender warm-season annual in the mint family, so it has no reason to go in the ground until the soil and air have warmed, and it grows fast enough to catch up.

Feed lightly, and only to a soil test

Give shiso a moderate feeding at planting and leave it at that. Get a soil test for the bed and follow its lime and fertilizer recommendation rather than guessing; if you are cutting leaves hard all season, a light second feeding is reasonable. Herbs grown for leaf flavor need only moderate fertility, and pushing them with nitrogen buys you soft growth rather than better leaves.

Pinch off the flower spikes as they appear

As soon as the spike-like flower clusters start rising from the leaf axils in late summer, pinch them off. Keep after them every week or so until frost takes the plant. Pinching the flowers before they set seed both keeps the plant putting its energy into leaves and stops the wind-dispersed seed that lets shiso escape the bed.

Pull the plants before the seed drops, and check for volunteers

Pull or mow shiso down before the seed heads mature, and walk the surrounding ground the following spring for volunteer seedlings. Hand pulling while plants are young is the whole job; let one season of seed drop and you will be at it for years. Shiso self-seeds prolifically and the seed travels on wind, which is how it has naturalized along roadsides and woodland edges; it is listed as invasive in Virginia, West Virginia, Tennessee, and Kentucky.

⚠ Do not let this plant reach pasture or a fence line grazed by cattle. Perilla ketone in the plant causes atypical interstitial pneumonia, and the plant grows generally more toxic as it enters its reproductive phase, when it flowers roughly July through September. Do not assume livestock will simply leave it alone: in fall, when forage quality and quantity drop, cattle congregate in the shaded areas where perilla mint tends to infest, which puts them at greater risk of eating it.

Cut leaves through the season, best just before bloom

Pick leaves for fresh use as soon as the plants are established and keep picking all summer. For the strongest flavor, take stems individually, cutting about 6 inches below the flower buds, in the stretch just before the plant blooms. The essential oils that carry shiso's flavor peak in the foliage just prior to blooming, and cutting stems rather than stripping leaves keeps the plant branching.