Shiso (Perilla frutescens), also called perilla, is an annual herb in the Lamiaceae, or mint, family, native to East Asia and grown in Kentucky gardens as a summer culinary crop rather than a perennial fixture. It's a staple in Japanese and Korean kitchens, used fresh in wraps and salads, pickled, or chopped as a garnish, and comes in both green and red-purple leafed forms with a flavor somewhere between basil, mint, and anise. Shiso is easy to grow and thrives in Kentucky's warm, humid summers, asking for little beyond a sunny spot and steady moisture. The main challenge isn't getting it to grow but keeping it from growing everywhere, since it self-seeds with real enthusiasm once a planting is a year or two old.
Sowing and planting
Start seed indoors 6 to 8 weeks before your last frost date, which in zone 6b falls around mid-April, pressing seed lightly into the surface of moist starting mix, since shiso needs light to germinate well. Germination can be slow and uneven, sometimes taking two to three weeks, and is improved by a period of cold stratification; refrigerating seed for a week or two before sowing often helps it along. Keep the mix consistently moist and warm, around 70°F (21°C), while seeds sprout.
Transplant outdoors after the last frost once the soil has warmed, typically mid to late May in Kentucky; shiso is frost-tender and sulks in cold, wet soil. Direct sowing outdoors is also possible once the soil is warm, though transplants give the season a head start. Space plants 12 inches (30 cm) apart in full sun to part shade, in rich, well-drained soil amended with compost. Water well at planting, and keep young plants consistently moist until they're established and visibly growing.
Growing on
Shiso wants steady moisture through the growing season; it wilts quickly in a dry spell and doesn't fully recover its best flavor even once watered again, so don't let the soil dry out for long between waterings. A light monthly feed with a balanced fertilizer keeps growth lush, though shiso isn't a heavy feeder in good garden soil. Pinch growing tips back regularly, especially early on, to encourage bushy, many-branched plants rather than a single tall stem, and keep picking leaves, which has the same effect.
Pinch off flower spikes as they appear if your goal is leaf production, since flowering slows new leaf growth and can turn the foliage more bitter. Left alone, shiso flowers and sets seed freely from mid to late summer onward, and this is where some care is worth taking: shiso is listed as a toxic pasture weed in Kentucky and can be dangerous to cattle if it establishes in grazing land. Grow it in a contained garden bed away from pasture or hay fields, and if you'd rather it not spread on its own, remove spent flower heads before they set seed.
Harvesting
Shiso doesn't have one single harvest date; instead you pick leaves continually through the season as the plant produces them, starting as soon as plants have enough foliage to spare, often within a few weeks of transplanting. Full-sized plants, reached at around 70 days, support the heaviest, most sustained picking, but individual leaves are usable well before that. Harvest in the morning when leaves are crisp, picking outer and lower leaves first to encourage the plant to keep branching and producing new growth from the center.
Leaves are best used fresh, since they wilt and discolor quickly once picked and don't dry particularly well for storage. For longer keeping, pickle leaves in salt or vinegar, or freeze them chopped in a little water or oil. The unopened flower spikes (known as hojiso in Japanese cooking) are also edible and traditionally used as a garnish or pickled whole; harvest them just as they begin to form, before the individual flowers open.
Problems and pests
Small, ragged holes in the leaves
Flea beetles chew tiny shot-holes in shiso foliage, particularly on young seedlings in late spring. Established plants generally outgrow the damage without treatment. On a young or heavily hit planting, a floating row cover laid over the bed at transplanting keeps beetles off until the plants are growing strongly.
Leaves chewed with large, irregular holes overnight
Slugs and snails target tender young shiso, especially in damp spring weather, often stripping seedlings before you notice the damage. Check under mulch and around the base of plants in the evening, and use shallow beer traps or iron phosphate bait if damage is heavy. Clearing nearby debris that gives slugs daytime cover also helps.
A white, powdery coating on leaves and stems
Powdery mildew develops readily in Kentucky's humid late summers, especially where plants are crowded or air movement is poor. It rarely kills the plant but can stall leaf production and make foliage unappealing to harvest. Space plants for airflow, avoid wetting foliage when watering, and remove badly affected leaves.
Plants bolting to flower early, with leaves turning bitter
Heat, long summer daylength, and drought stress all push shiso to flower earlier than you'd like, and flavor turns more bitter and less tender once a plant commits to blooming. Pinch flower spikes out promptly to delay this, and keep plants well watered through hot stretches, since drought stress is often the trigger.
Volunteer seedlings coming up everywhere the following spring
Shiso self-seeds extremely readily, and a bed left to flower and set seed the previous year can produce a thick carpet of volunteers the next spring, often well beyond where it was originally planted. This habit is also why shiso is considered a toxic pasture weed in Kentucky: established plants in grazing land are dangerous to cattle. Thin or weed out unwanted volunteers while they're small, keep plantings away from pasture or livestock areas, and remove flower heads before they set seed if you want to limit spread.
Varieties worth growing
- Green Shiso (Ao-Jiso) – the classic Japanese culinary type, with bright green, crinkled leaves used fresh in wraps, salads, and as a garnish.
- Red/Purple Shiso (Aka-Jiso) – deep burgundy leaves rich in anthocyanins, traditionally used to color and flavor pickled umeboshi plums; the color bleeds attractively into vinegar or syrup.
- Korean Perilla (Kkaennip) – a related culinary form grown for broader, more savory-flavored leaves, traditionally used whole as a wrap in Korean cooking.
- Crispa (frilled) types – ruffled-leaf forms grown as much for ornamental texture as for the kitchen.
- Britton – a compact, bicolor selection with green leaf tops and purple undersides, grown for ornamental borders as well as culinary use.