How to grow shiso in Australia

Shiso is frost-tender and germinates best in warm soil, so the window opens once the last frost has passed and the ground has warmed to at least 18°C.

Tropical and subtropical (Darwin, Brisbane): Plant through the warmer months, roughly August to March. It grows fast here and will self-seed readily, so give it room.

Warm temperate (Sydney, Perth, Adelaide): Sow from September through summer. This is an easy climate for shiso and you can get two or three sowings across the season.

Cool temperate (Melbourne, Ballarat): Wait until the frost risk has cleared, usually October, and sow through to January. Starting seed indoors four weeks earlier gives you a head start.

Cold (Hobart, Canberra, alpine): A short-season crop here. Start seed indoors in early spring and transplant out only once nights are reliably above about 10°C.

Arid (Alice Springs): Plant in the milder shoulder seasons, spring and early autumn, and give it afternoon shade through the hottest part of summer.

Shiso seed needs light to germinate, so surface-sow it and press it gently into the mix rather than burying it. Keep the surface consistently moist until seedlings appear, which usually takes one to two weeks. Germination can be slow and patchy, so sow more than you think you need.

Start in trays or sow direct once the soil is warm. Thin or transplant seedlings to about 30cm apart. Pinch the growing tips once plants reach 15 to 20cm to encourage a bushy shape and more leaf. Rich, moisture-retentive soil with plenty of compost gives the best leaf production.

Shiso is a good container herb and does well in a medium pot on a balcony or by the kitchen door, which also makes it easy to keep the self-seeding in check. Use a quality potting mix and keep the water up in summer.

In garden beds it grows into a soft bush around 40 to 60cm tall. Give it a spot with rich soil and it will reward you with months of leaf. Just be aware that any flowers you let set seed will produce seedlings the following season, so pull the flower spikes early if you do not want it spreading.

Part sun to full sun suits shiso, with around four to six hours of direct light a day being plenty. In hot inland gardens it actually prefers some afternoon shade, which keeps the leaves tender and slows bolting.

Water consistently. Shiso wilts quickly when dry and the leaves toughen if it is stressed, so aim for evenly moist soil and mulch to hold moisture through summer.

Start picking leaves once the plant is established, usually around eight to ten weeks from sowing. Harvest from the top down, taking the younger leaves and pinching just above a leaf pair to keep the plant branching. Regular picking keeps it productive and delays flowering.

As the season shortens the plant will send up flower spikes. The flower buds and seed heads are edible and used as a garnish, but once it flowers heavily the leaf quality drops, so this is the point to either let a plant or two set seed for next year or pull it out.

Shiso is largely trouble-free. The main issues are slugs and snails on young seedlings, and aphids on soft new growth, both of which are easy to manage. In very hot weather plants bolt to flower early, which you slow by picking often and providing afternoon shade.

One thing to be aware of beyond the garden: the plant contains perilla ketone, which is toxic to grazing animals such as cattle and horses, and is best kept away from pets that may chew large amounts of foliage. This does not affect normal culinary use by people.

Shiso sits well alongside tomatoes and other summer vegetables, and its aromatic foliage is thought to help confuse leaf-eating pests. It also works near brassicas like cabbage. There are no strong plants to avoid, though like most herbs it does best with a little space rather than crowded in among vigorous neighbours.

Is shiso hard to grow?

No. The only tricky part is germination, since the seed needs light and can be slow. Surface-sow it, keep it moist, and once it is up it is an easy, fast-growing herb.

Why has my shiso started flowering?

Shiso flowers as the days shorten in late summer and autumn, and sooner if it is heat-stressed. Pick leaves regularly and give afternoon shade to delay it. Once it flowers heavily the leaves lose quality.

Does shiso come back every year?

The plant itself is an annual and dies off after flowering, but it self-seeds so readily that it often reappears in the same spot the following spring if you let a few seed heads mature.