Persicaria tinctoria / Polygonum tinctorium likes a neutral, well-drained soil, full sun, and weekly watering. This is the first of two posts on how I start and transplant indigo. It is not the only way – seeds could be started in flats or directly in planters/pots, etc. There’s really no right or wrong so long as your indigo gets lots of sun, enough water and fertilizer.
Start seeds in greenhouse 5-6 weeks before last frost date for earliest outdoor planting – late March for us.
The soil is tilled and mixed with composted manure, green sand, and a balanced organic fertilizer.
You want to level the surface of the seedling bed to keep water (and seeds) from pooling in one spot. Make your bed narrow enough so that you can easily weed it.
Broadcast seed densely on soil, sprinkling on top of bed. You want about 1 seed per 1/4″ square.
Cover with about 1/8″-1/4″ sand – enough to hold the seeds in place – and tamp/pat down firmly. Spreading sand over the seeds to hold them in place & help keep them moist for sprouting. The sand also makes it easier to pull up the seedlings for bare-root transplanting.
Cover the bed with seedling cloth (like agribon AG-19) to keep frost/wind/bugs out and moisture in. While this isn’t necessary, it helps for growing healthy starts.
The seeds are watered in well and then watered once a day until transplanting.
The plants are kept covered until they are big enough for transplanting. In order to not stunt or deform them, the seedling sheet must be loosened from time to time to make more room for the growing plants.