Shiso is a weed out here! I see the red form ( also known as Perilla crispa) growing by the roadsides and it can self seed like mad.
Shiso, Perilla frutescens, does have some quirks. The seed germinates better after the dry seed has been frozen for a while. Light is generally needed for germination, so press the seed into the soil’s surface and keep it misted. After a day or two in the sun, getting light, it can be barely covered. The light and cold deactivate germination inhibitors. Eventually, the inhibitors break down, but it might take a long time without the cold>light.
Shiso isn’t crazy about being transplanted, so sow the seeds where you want them and thin them to around 12-18 inches (30–45 cm) apart. A well-draining, rich soil that is SLIGHTLY acidic, pH 5.5–6.5 works best. The more you harvest, the more nitrogen-rich fertilizer it will need.
Shiso plants tend to be short-day; as the day length gets shorter, it’ll start going to seed, so plan on harvests while the days are long or grow it under strong plant lights.
