Grow petchoas in full sun (at least six to eight hours of direct light a day). They can tolerate some partial shade, but they won't bloom as well and are more likely to get lanky, unattractive stems without enough sun. Like most flowering annuals (including petunias and calibrachoas, to which they're related), petchoas prefer moist, well-drained soil rich in organic matter if you grow them in gardens. Water them regularly to keep them from wilting ,but take care not to overwater. The soil should never stay wet or soggy, otherwise the roots could rot.
Fertilize petchoas regularly during the growing season or make it easy on yourself and use a slow-release fertilizer at planting time. Slow-release fertilizers deliver a little bit of nutrients to the soil each time you water and you only need to apply them once a season.
You typically don't need to worry about pinching or pruning petchoas to keep them pretty, through you can if you'd like to encourage more compact growth.