By Ashley Walker
Copyright (text and images) Nature’s Rainbow unless otherwise credited. 7th December 2023.
This year has been difficult with erratic weather plus numerous unplanned happenings distracting us. So it wasn’t until the end of October that we finally returned to the Groundswell site to see what had become of the Groundswell dye plot. This was started off for Groundswell 22 (see here) and (here) and extended for Groundswell 23. For nearly five months now the plot has fended for itself, but amazingly it looked pretty good at first sight. I had expected it to be overgrown with weeds and looking pretty sad but no!
Now before I get into the detail you might be wondering why I’m bothering to write another update on this plot. Like most gardeners I don’t get much experience of growing plants away from home. Our growing spaces include two allotments and a very small urban garden, which like most such growing spaces have rich soils and are generally in sheltered situations. Ours are located within a mile of each other and suit our car-free existence very well. But ecology, micro-climate and soil type can differ markedly between sites even a few miles apart, and plant growth can be very different indeed! If I am to advise others on dye plant gardening I need to broaden my experience as much as possible. The Groundswell plot is a terrific opportunity for this.
So to remind past readers and inform new ones, this plot was created at the edge of a fairly typical farmer’s field up on the chalky high ground of Hertfordshire. The thin well-drained chalk soil is full of flints and is humus/nutrient poor – the result of many years of conventional farming. The farmers here have a mission to restore the soil fertility using regenerative agricultural techniques but this is a work in progress. Prior to the growing of dye plants this tiny bit of land had not been ploughed for a few years and was being used to grow a “herbal lay” which includes grasses, clover, chicory, great burnet and some additional plants. The site is quite exposed to the weather and gets full sun. It is fenced off from the rest of the field which is used to host the annual Groundswell Regenerative Agricultural festival held in June and can be used as grazing during the remainder of the year.
The plot was created by stripping off the existing vegetation. About an inch of the top soil was removed in the process. The soil was then dug over by hand with an ordinary garden spade and a few bags of animal manure compost were added in before planting. The sowed seed and transplants were watered a few times prior to the Groundswell event but not at all afterwards. I should point out that apart from a hot and dry June the rest of the Summer and Autumn of 2023 have been wetter than usual.
Dyer’s Coreopsis (Coreopsis tinctoria)
This North American prairie plant was grown in 2022 from directly sowed seed but not all of the seedlings subsequently flowered. Some remained as juvenile rosettes throughout the hot and parched summer of 2022 and the subsequent cold winter. This was a surprise to me as in previous years all of the plants grown in our main dye garden have flowered and died in the same year. These long-lived plants at the Groundswell plot went on to produce much larger specimen plants than usual which flowered this year (2023). In the photo you can see the thick stems of these plants. I’m not certain why these few plants remained in the rosette stage. It could be they were stressed either by the extremely hot summer of 2022 or by the poor soil quality. But now I see that some of the Dyer’s Coreopsis plants are doing the same thing this year which gives me the idea that this is actual a fairly normal growing strategy with a few plants going through the winter to flower the following year, as a sort of insurance against seed failure. This begs the question: why don’t the plants in our main dye garden do this? Possibly the allotment soil is too rich or, perhaps more likely, the varieties of Dyer’s Coreopsis I’ve been growing are different. The varieties planted at the dye garden allotment have been highly bred for decorative qualities and are not as hardy as the Dyer’s Coreopsis at Groundswell which was originally purchased from a commercial supplier of bulk wild flower seeds. I also notice that the plants grown from the wildflower mix produce larger seed heads with more seed, so they are definitely different.
The Dyer’s Coreopsis seed we will be selling in late 2023/24 will be seed saved from the hardy stock.
Japanese Indigo (Persicaria tinctoria)
This was the big surprise. The plants had grown well despite all the neglect and lack of any watering. I had grown three varieties Senbon, Kojyoko and Chijimiba. All were now in flower, although the Chijimiba had been flowering a lot longer than the Senbon. This confirms my speculation that these plants are perfectly capable of being grown in the UK on a field scale without maintenance. The poor performance of the Woad plants demonstrates that there are places in the UK where Japanese Indigo would generate a higher indigo yield.
Just to skip back to 2022 where I grew Japanese indigo in the same location. The weather that year was hot and parched and the plants were stunted due to lack of water but they did survive and although the crop would have been poor there still would have been a crop which is more than could be said for some plants! Clearly the East of England on an exposed chalk hillside is not the best place to grow Japanese Indigo but if it’s possible to grow it here then it can be grown to great advantage in wetter, fertile soils elsewhere in the UK.
The Chijimiba has shown itself as an early and prolific flowerer. Looking at the soil surface under the plants I could see flower heads lying on the ground where mice had cut through the stems to eat at the seed on the ground.
African Marigold (Tagetes erecta)
By late October these plants were almost over. As the previous year had shown these plants, despite their attractiveness to slugs (which infest this plot), are still capable of putting on a good show when left to their own devices. As long as the seedlings are grown to a sufficient size (about 15cm high) before being planted out they will generally be able to survive. Admitedly some of the plants had been chewed to death. I suggest these had become sacrificial allowing the others to survive. For maximum chance of survival it is best to plant a lot in the same area, rather than dotting them about individually.
I put one of these annual plants in on a whim and did not expect much from it. I should have read the label! This one has not grown as tall as the plants we have in the main dye garden but it has still managed to get up to a couple of metres. With the shelter of the dye garden some of our plants have reached between 3 to 4 metres. Native to Southern South America Tagetes minuta is naturalised in many parts of the world including Mexico. It has some very interesting properties indeed and is grown as a crop in some parts of the world. It has a very pungent smell which appears to discourage aphids if the leaves are placed in contact with an aphid infected plant. I have tried this on brassicas in a polytunnel and it does indeed work. A spray made from the leaves may be worth trying. It is also said to release chemicals from its roots which reduce the growth of bindweed and ground elder.
So far the mild frosts we have been having have not damaged the plants. Tagetes minuta flowers very late in the year (November in the UK) and produces a yellow or yellow brownish dye and is an excellent source of tannin. But think twice before growing this giant! It could become invasive in a warmer climate and is considered a problem plant in parts of China.
Woad (Isatis tinctoria)
Last year I planted two square metres of ground with woad. The first m2 was filled with transplants and the second with seed. Neither did particularly well in the hot dry conditions but the transplants were the best. Most of the plants grown from directly sown seed were dwarfed and feeble. This continued to be the case in the following year despite the addition of some fertiliser. The plants simply didn’t get any larger. In addition very few of these plants produced flowers, remaining in their juvenile state at the end of October, 18 months later. Why?
At the moment I can only speculate.
- The seed was sown too thickly and the plants struggled in competition with each other for the sparse nutrients. This theory is prompted by the fact that transplants (with good spacing) grew better. This is certainly a factor but it does not explain all of the poor growth. I have sown many plots thickly before at the dye garden and although each individual plant is smaller overall, the plants are capable of doing well even in crowded conditions.
- The soil structure prevented Woad’s tap roots from going deep. This is entirely possible. Years of ploughing may have produced a “hard pan” about 30-40cm below the soil surface which hinders root growth. This theory is also backed up by some other evidence. Those plants which did flower during the Spring, when pulled out, had clearly put most of their energy into producing shallow side roots. Regrettably the only way for me to test this theory would be to double dig a further patch and break up any pan below the surface.
- The soil was nutrient poor. This theory I can dismiss easily as I had dug in a good quantity of fertiliser before sowing and the Japanese Indigo, which is also a nutrient hungry plant, did not have any trouble.
For 2023 I sowed a further m2 with seed but despite the wetter weather this remains very disappointing indeed. Also I would have expected there to be a lot of self-seeded Woad plants on the plot by now as I have not removed the seed heads from earlier in the year but there were remarkably few.
If I were to only take the evidence provided by this one plot, I would without hesitation decide to grow Japanese Indigo rather than Woad as my main source of indigo dye.
Chinese Woad (Isatis indigotica)
Out of curiosity I also planted a couple of Chinese Woad plants in amongst the Common Woad. These plants grew about as well as the other Woad transplants and one was in the process of flowering when we looked at the plot in October.
Weld (Reseda luteola)
Another disappointing result! In 2022 one m2 was planted out with weld seedlings (grown in modules to minimise root disturbance when transplanted). These plants initially grew well but most flowered in the first year and failed to reach the sort of size that I’ve come to expect. Seed from these plants scattered on the ground and I expected self-sown plants to appear in the Autumn of that year but less than a handful made an appearance and these appeared to have been eaten during the winter. In spring of 2023 I planted up 2m2 with weld and sprinkled a further m2 with seed – none of which came up. The transplants also grew well to begin with but also flowered early and by October 23 had died leaving only a handful of self-seeded baby plants behind.
Weld has a deserved reputation for being a tricky plant to grow. At times it seems the plant will only grow when and where it wants to. Weld produces hundreds and thousands of small black seeds which implies that it expects to lose the great majority to predation or being crowded out by other plants. When sown in seed trays or modules there is typically around 100% germination. So clearly when directly or self-sown the great majority of seeds fail.
So what could be done to increase the success?
I have previously successfully sown Weld seed directly on waste ground where the vegetation had been removed leaving a bare surface. However, a great many seed are still needed to obtain just a few plants. The time of sowing is fairly critical. Sowing early in the spring gives the plants plenty of time to produce flowers in the first year, which is not such a good idea if you want to get large plants. At the Groundswell site I was constrained by the need to produce a good display in June 2023, so I had to start the plants off very early and they did flower from plants in the same year. The best time to sow for large plants in the second year is probably late Summer. As for predation of small direct sown seedlings there is nothing much that can be done other than making sure the ground is clear of all other vegetation and relatively slug and snail free. It has been suggested that Weld plants could be grown with cereal crops but I doubt this would work. Every time I have planted weld seed or transplants mixed in with other types of plant the Weld has died. So to sum up, growing Weld on a field scale is not going to be easy!
These make up the bulk of plants in the dye garden.
We have three species of Golden Rod growing in the plot.
Solidago Canadensis (Canadian Golden Rod)
Planted in 2022 this North American native was growing very well indeed and had expanded into a large mature plant. This is unsurprising as this species has become invasive in the local area and can often be seen growing on waste ground and as a garden escape. It has shown itself to be highly robust needing no maintenance whatsoever. Probably the best of the Solidago species for dye.
Solidago Speciosa (Showy Golden Rod)
Taller than the Canadian species with larger flowers, this species has also matured into a large plant. The longer flower stems are prone to falling over so not as well behaved. Otherwise it is also very robust and needs no maintenance other than a bit of support when flowering.
Solidago virgaurea (European Golden Rod)
This is a new species to us but one I’m encouraging others to grow because it’s native to this country. The plants shown above were grown from seed in modules and transplanted to the plot in late May where they have thrived. One was even flowering in October in its first year. Virgaurea is a much smaller Golden Rod but has the same large flowers as Speciosa. It may make a pleasing garden plant, as this again appears to be very robust. However, as a much smaller plant it could be crowded out by its cousins from across the water. We have not grown this plant long enough to take a harvest to test out its dye value.
Dyer’s Greenweed (Genista tinctoria)
Planted in 2022, this Dyer’s Greenweed has gone from strength to strength despite some animal damage in its first year. This is another low maintenance dyeplant with one caveat. The small seedlings need to be grows out of reach of voracious slugs and snails before being planted out. I am beginning to think that for large scale field trials, Genista tinctoria may be a lot less hassle than Weld. Coupled with the fact that it’s a nitrogen fixing member of the Fabaceae it could make a useful addition to an agroforestry system. Note: Genista tinctoria is often described as a low growing shrub growing to a maximum of 60cm high. The variety we grow can get to 1.5m and may be a subspecies called virgata. We recommend that if you grow for dye then you need the larger variety.
Dyer’s Chamomile (Cota tinctoria)
I described this earlier in the year as the ‘star of the show’ for its ability to grow well even in hot dry weather. This was the only dye plant that thrived in last year’s drought. This year it has continued to grow well and most of the plants show every sign of going on to a third year without dying. In our main dye garden these plants usually die in the mid-summer of their second year.
Normally a good self-seeder I decided to set aside a 1m2 area for sowing seed direct. But a month after sowing, nothing had appeared so I planted some other dye plants. Chamomile, like Weld, normally produces a very fertile seed. Therefore the problem with direct sowing is something to do with the conditions and not the seeds. There are a few self-seeded Dyer’s Chamomile plants growing here and there on the plot, but not anywhere near as many as I expected. I put this down to slugs eating the small baby plants.
Madder (Rubia tinctorum)
Madder is usually slow to get going and the plants on this plot are no exception. I have seen Madder grow sufficiently to produce some good thick roots in only two years but only on fertile soil and under ideal conditions. Out here in crowded conditions on poor soil, expansion has been slow. The tops were in fairly bad shape by the end of October but that is no different to the plants we have in our main dye garden. What the roots are doing I don’t yet know. Origially the Madder, Dyer’s Woodruff and Lady’s Bedstraw were all planted very close together and now really need to be given more room. But otherwise all are growing well.
Wild Madder (Rubia peregrina)
I put one plant in and this is still alive but like saw-wort it’s a very slow grower and really needs to have its own bed. In its native habitat, on the coasts of South Wales and the south west of England, it seems to cope well growing amongst large shrubs and even small trees. It sends out long stems which scramble up other vegetation to get at the light.
Dyer’s Woodruff (Asperula tinctoria)
This has grown well despite the crowded planting and when I looked closer I discovered a good number of seeds on the now yellowing tops.
Lady’s Bedstraw (Galium verum)
As expected this native to the local area has expanded more than the Asperula tinctoria and Common Madder and looks set to expand out of the plot all together. A good number of seeds were produced so I expect to see some seedlings next year.
Lance Leaved Coreopsis (Coreopsis lanceolata)
Of all the perennial coreopsis species, I’ve found that Lanceolata is possibly the most hardy. Having said that, getting through the winter in this exposed position will be a test. In October 2023 the plants were still producing a few flowers and generally looking quite happy.
Sweet Mace (Tagetes lucida)
In its native Mexico this low growing plant is a perennial but here it does not get through the winter so it is best grown as an annual. I should have planted it around the edge of the plot because it has slowly been crowded out by larger plants. Still alive in October but now hardly noticeable squeezed amongst the other plants. It makes a fantastic bedding plant with a prolonged flowering period from Late June to September. It is a great culinary herb as well as a useful dye plant. Malu Colorin from Talu Earth visited the dye garden in 2022 and told us it grows wild in Mexico and used in a similar way to Weld in the European dye palette.
Saw-Wort (Serratula tinctoria)
This native relative of Knapweed continues to grow but it’s fairly clear that if left alone for much longer it will be crowded out altogether. I planted two plants last year and one this year. All plants are still alive but struggling as larger surrounding plants have crowded out their light. A few decades ago this species was on the endangered list. Its slow growing habit makes it highly vulnerable to traditional farming techniques and of less use than faster growing yellow dye plants. It is however very good for insects and makes an attractive garden perennial.
Murasaki (Lithospermum erythrorhizon)
As we expected, these plants have done very well on the plot. However, not long after planting we discovered that the best conditions for development of the purple dye in the roots is deep shade. So although it looks very happy in full sun, it’s not going to provide much if any dye in this position. Therefore this plant should be grown in woodland.
Tansy (Tanacetum vulgare)
The tops of Tansy die back quite early in the year so not much is left above ground at this time except for the dead flower stalks and a few surviving leaves. However, the plant has clearly done well and has started to spread via its underground shoots. It prefers a wetter climate than here but could still do well enough to become invasive. We will monitor this plant’s spread at this site.
Weeds and Pests
There are not many weeds on this plot because it is part of an arable field given over to a herbal lay. A few Sow Thistle seeds from the adjacent hedgerow have seeded in the plot. The brambles are also waving their tentacles menacingly but these can be cut back. The most invasive plant is clover from the herbal lay. Clover sends out runners which root very easily and hold on tenaciously.
Pest-wise the main danger continues to be slugs. The field is full of them and they take a toll particularly on young plants. Most of the dye plants can and do survive fairly well once they have grown to approximately 15cm high. So far there have been no signs of any insect attack but the mice clearly like eating the Japanese indigo seed. So far I’ve been unwilling to remove the fence around the plot, in case of herbivore attack. However but the plot had recently been visited by a large animal (see below), although I’m not entirely certain what. It had jumped over the fence, left track marks and scat but the prints were a little too old to provide definite identification. The good news is that none of the dye plants were eaten.
- A larger scale test crop of Japanese Indigo is now required.
- Weld may not be the best source of yellow dye in this location and further tests comparing Weld and Dyer’s Greenweed are required.
- A further investigation of why Woad has performed so poorly needs to take place which may involve double digging to remove any soil pan and giving individual plants more space.
- At some point I just need to bite the bullet and remove the fence all together.