Grow Shiso From Seed: Easy, Stunning Tips for Fresh Leaves

Grow shiso from seed for a steady supply of fragrant leaves in green or purple varieties. This warm-season annual, also called perilla, grows well in garden beds and containers. Its seeds can take time to sprout, but with warmth, moisture, and a little patience, you can raise healthy plants for fresh picking through summer.

Starting perilla from seed

Shiso seeds often germinate unevenly, especially when they are old or have dried out during storage. Fresh seed usually gives the best results. Check the packet for sowing directions, since treatments and germination times can vary by seed source.

Start seeds indoors about four to six weeks before your area’s last expected frost, or sow them outdoors once the soil has warmed and frost is no longer a concern. Shiso dislikes cold conditions, so wait until nighttime temperatures are reliably mild before setting out seedlings.

Fill a seed tray or small pots with moist seed-starting mix. Press the seeds onto the surface and cover them with only a thin layer of mix, since shallow sowing helps them receive light. Keep the mix evenly moist, not waterlogged, and place the container somewhere warm. A temperature around 70 to 75°F (21 to 24°C) is a reasonable target.

Shiso germination may take one to three weeks, and some seeds may sprout later. If seeds do not come up right away, keep the surface moist and give them more time before starting over. Once seedlings appear, provide bright light. A sunny window may work, but a grow light can help prevent young plants from becoming tall and weak.

When seedlings have several sets of true leaves, thin them or move them into individual pots. Handle the roots gently, and keep the young plants in a protected spot until it is time to transplant. Harden them off by setting them outdoors for gradually longer periods over about a week.

Choose a sunny, warm planting place

Shiso sunlight needs are straightforward: plants grow best with at least six hours of sun, though they can tolerate some afternoon shade in hot climates. Too much shade can lead to lanky growth and fewer leaves. Choose a spot with well-drained soil; standing water can damage the roots.

Work compost into poor soil before planting, but avoid adding excessive fertilizer. Rich soil can encourage leafy growth, while too much nitrogen may produce soft plants with less concentrated flavor. Water after transplanting and keep the soil from drying out completely as the plants establish.

For shiso plant spacing, leave about 12 to 18 inches between plants. A little more room improves airflow and makes it easier to pick leaves. If you are growing several plants in a row, leave enough space to reach between them without crushing stems.

Green shiso and purple shiso have similar growing needs. Green varieties are common in Japanese cooking, while purple forms bring color to gardens and dishes. Check seed descriptions for growth habit and mature size, since cultivars can vary.

Growing shiso in pots

Shiso pots are a good choice for patios, balconies, and small gardens. Use a container with drainage holes and enough room for the roots, ideally at least 10 to 12 inches wide and deep for one plant. A larger pot can hold more than one plant if you leave adequate space between them.

Fill the container with quality potting mix rather than garden soil, which can become dense in a pot. Place it where the plant will receive sun for much of the day. Containers dry out faster than garden beds, especially during hot weather, so check the soil regularly and water when the top inch feels dry. Empty any saucer beneath the pot after watering so the roots do not sit in water.

Potted plants may need occasional feeding if they are growing in the same mix for a long season. Use a balanced fertilizer according to its label, and avoid frequent or heavy applications.

Keep plants leafy with regular picking

Once a shiso plant is about 6 to 8 inches tall, you can begin harvesting individual leaves. Pick from several parts of the plant rather than stripping one stem bare. Regular harvesting encourages branching and keeps the plant compact.

For a larger harvest, cut leafy stems just above a pair of leaves. Avoid removing more than about one-third of the plant at a time, especially when it is young. Wash the leaves before use and store them loosely wrapped in the refrigerator. They are most fragrant when fresh, so pick what you expect to use soon.

If you want the plant to produce seed, allow some flower spikes to form late in the season. If you prefer a longer supply of tender leaves, pinch off flower buds as they appear. Flowering signals a shift toward seed production, and leaf growth may slow.

Prevent unwanted self-seeding

Shiso self seeding is common when flowers mature and drop seed. In a garden, a few volunteer seedlings can be useful, but they may appear in places where you do not want them. Remove flower heads before seeds ripen if you want to limit next year’s plants, and pull unwanted seedlings while they are small.

Perilla can spread beyond cultivated beds in some areas. Check local guidance before letting it set seed, particularly near natural areas or pasture. Keep plants away from livestock, since perilla can be harmful to grazing animals.

With warm soil, steady moisture, and regular picking, shiso is a rewarding plant to raise from seed. Start with fresh seed, give seedlings time to emerge, and choose a sunny bed or roomy container. Once established, the plants provide fresh leaves throughout the growing season and may return as volunteers if you allow a few to set seed.