This blog post is about growing and harvesting Persicaria tinctoria. I bought some dye plants online in Italy while I was on holiday last year. The reason for this is that I couldn’t get hold of the seeds or cuttings online in the UK. If I do it does cost quite a lot. Then I found some online suppliers online called Erika Caldera. The website and communication are in Italian. I got the order using google translate on my computer. Delivery was fast and efficient to an Italian address. Among them were madder root and Polygonum tinctoria. It is also known as Indigo tinctoria, Japanese indigo, Dyer’s knotweed, and Polygonum tinctoria. It is believed to give more stable blue color than woad ((Isatis tinctoria). This dye plant grows in Japan, uses a lot in traditional Japanese indigo shibori fabric dyeing design. It is easy to grow and produces deep shades of blue similar to those from Indigofera species. It is a temperate climate-friendly as great news to grow in the UK.
Growing and harvesting Persicaria tinctoria
As it is my first attempt in growing this dye plant I bought a young plant in August. I have not to experience growing it from seed. However, I found out the seeds are only viable for a year. Personally, if I could I would just buy cuttings as they are just so easy to root. I grew this young plant in a pot as I would like to bring it indoors come fall to let it flower and seed. This dye plant is not frost friendly. Even there is no viable seed at least I would have a plant that produces young shoots easily.
For this Japanese indigo to produce more leaves once the leaves are harvested just bent the branches over and cover it with compost. It will then produce more young shoots. I grew in a pot of well-drained mixture of manure and coconut compost. It doesn’t need much care except watering and it is relatively disease free.
Once the leaves mature come end of summer and fall harvest the leaves for dyeing every two weeks. The leaves can be used fresh or dried. i will write another blog post on how to extract blue dye from Persicaria tinctoria.