Growing American Pokeweed in the UK
Phytolacca americana
By Ashley Walker
Copyright 20th January 2020
First a warning. All parts of this plant are poisonous to humans and most animals except birds. It is also invasive so its growing must be carefully controlled.
I had heard a lot about this controversial dye plant, but in the UK it’s still much of a novelty. So when I spotted some plants growing in a greenhouse nursery in Devon in 2018 I “obtained” a berry containing a few seeds. I grew them last year (2019) just to see for myself what all the fuss was about.
Horticulture
Three of my seeds sown in April germinated after about 2 weeks.
The three seedlings of American Pokeweed showing seed leaves and red stems
By June the plant in the greenhouse was already looking like a lush spinach plant.
The pink stemmed seedlings were very vigorous and had to be potted on after a few weeks. By the time I judged it was warm enough to plant out in May/June the plants were already around 10in high. My first observation was how similar they look to our native Deadly Nightshade (Atropa belladonna) despite belonging to a totally different plant family. Pokeweed is sometimes called American Nightshade and I think this is not just because of its toxic qualities.
Not taking any chances with late frosts I planted one of the plants in our greenhouse and the other two outside in the garden. The plant in the greenhouse grew with extraordinary rapidity, its reddish stem swelling out to more than 2 inches in diameter. By the Autumn it had escaped through the window in the greenhouse roof reaching 7ft. An extraordinary “triffid” of a plant! Outdoors the plants did not do so well only growing to about 4ft.
By October the plant had escaped though the greenhouse window and was threatening to take over the whole greenhouse.
The pink flower stems are quite attractive.
The berries of American Pokeweed start as green then turn pink and finally black at which point they are ready to be used to dye.
This photo shows the other variety of Pokeweed with short “club like” racemes of berries. Spotted growing at Bell House.
A slightly out of focus shot of the mature American pokeweed plant growing in the Horniman’s museum dye plant garden showing short upright racemes of ripe berries.
There are several cultivars of pokeweed available commercially – the chief difference between them appears to be the shape of the flower and berry racemes. In one type the racemes are short, upright and club-like (sometimes given a separate species name P. rigida) and in the more decorative type they are long, thin and pendulous. The plant is a herbaceous perennial native to North America which can reach 10ft in a single season before dying back to the ground during the winter.
Our variety is the one with long thin pendulous racemes. Later in the year we found plants of the other variety growing at the Horniman museum dye garden in Forest Hill, South London and in the gardens at Bell House, Dulwich. At Bell house it grows as a weed which demonstrates how invasive it can be.
Dyeing Method
Once the berries had ripened and turned black I picked a few racemes and test dyed on a small piece of alum mordanted wool yarn. Internet advice indicates that the best method is to make a dye bath from several times the weight of fibre to be dyed in berries, heated with the strongest acetic acid you can get hold of. I had some 10% acetic acid left which I bought to fumigate an old bee hive. At this strength the vapour alone can rust steel so caution is required. Distilled white vinegar is probably the next best thing. The yarn quickly took a very pleasing bright red colour (much quicker and easier than madder) but the big question was how long would it last? Some dyers say it can last years and others say it fades within a matter of weeks. I hung up my sample in the window with half of it covered in foil to keep the light out.
Light fastness
After about 80 days I took it down and had a good look at it. The wool exposed to the daylight had indeed faded with the side facing the outside more faded than the side facing inwards. What is more the red is fading to a disappointing brown (in the photo it looks more orange than it actually is). The window is incidentally a north facing one so it would presumably fade even quicker in direct sunlight. The covered part of the sample still shows a good red. From experience of other fugitive plant dyes I would guess that textiles dyed with pokeberry could be made to last a few years if kept in the dark and only worn intermittently indoors. But I’m not sure it’s worth it. When freshly dyed the colour is fabulous and I’m sure that when the native Americans used it to dye their ponies they made a glorious (and terrifying) sight. But coupled with the potential hazards of growing the plant I think that its continued inclusion in our dye garden is in the balance. Susan is all for eradicating it immediately so it’s on borrowed time!
The upper part of this wool yarn sample was exposed to light in a North facing window for 80 days. The lower part which was wrapped in foil remains a good red while the exposed part has faded to brown (in this photo brown looks more orange than it really is.
This photo (taken indoors shows the side of the yarn that was facing the window which has suffered the most fade.
This side of the wool yarn was facing inwards and has suffered less fade. The bottom part was covered in tin foil and has suffered little or no fade.
Conclusions
The plants growing outside managed to resist light frosts but have since died back to the ground. By January the plant protected from the frost in the greenhouse still has green leaves. Information on the web says that the plant mainly reproduces by seed (which can remain fertile for 50 years) but it can also shoot from the roots. There is no doubt that my greenhouse plant has produced many long side roots and the plant is clearly making a bid to take over the whole thing. No doubt the phenomenal growth uses up a lot of soil nutrients too.
On balance I think that where pokeweed grows wild (in North America) and berries can be obtained in quantity via foraging, it can be a fast, fugitive and fun plant dye, but as a dye plant in the UK it’s probably not worth planting it, not when a good permanent red can be got from madder.
Additional information on Pokeweed can be found here:
https://www.fs.fed.us/wildflowers/plant-of-the-week/phytolacca_americana.shtml
http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=220010427
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=27983
Horniman Museum Dye Garden:
The Horniman museum Dye Plant Garden is well worth a visit.
https://www.horniman.ac.uk/get_involved/blog/planting-our-dye-gardens
Bell House Gardens:
American Pokeweed berries beginning to ripen.