By Ashley Walker
Copyright (text and images) Nature’s Rainbow unless otherwise credited. 25th April 2023.

I managed to return to the Groundswell dye plant plot last week (Friday 21^st April 2023) to see what state it was in after six months of neglect, the coldest winter and wettest spring we have had in a decade. What I found was very instructional with some surprises.

So, just to recap, this small dye garden plot was created in an exposed agricultural pasture field last year in early May for the Groundswell Regenerative Agricultural Show held at Weston in North Hertfordshire. Its purpose was twofold:-

• to try and interest farmers in growing dye plants on a large scale.
• to see which plants grew best on this exposed site.

A full report of the first years progress can be read here.

Woad (Isatis tinctoria)

Two 1m² beds were planted with Woad last year, one with plants and the other with seed. Neither did particularly well last year because of the drought. The seeded area was particularly poor and frankly the plants have not improved since. So small that you could easily mistake them for first year seedlings rather than 1 year old plants.

The patch with transplants on the other hand was looking about as you might expect from the time of year though the flower spikes are not as tall as the plants in our allotment dye garden.

What does this tell me about growing Woad?

This is a poor site for growing Woad! It’s true that the drought and extreme heat last year stopped the Woad in its tracks. Sowing in May was probably a bit too late but the main problem was lack of rain. The exposed pasture dried out too quickly so I conclude that any attempt to grow Woad here on a large scale would be very risky indeed. A farmer would probably need to irrigate to guarantee a decent crop as the chances of low rainfall would in most years prevent the Woad from growing to a harvestable point. In addition the chalk soil may be poor in nutrients leading to weaker growth (though perhaps only by garden standards). Having said that there will be a larger scale field trial at Groundswell this year and so far the rain has been with us.

Interestingly most of the plants grown from directly sown seed last year have remained in their first year “Rosette” state so there remains the possibility they will grow large enough to be harvested this year.

Weld (Reseda luteola)

This proved interesting on two scores.

First the two 1m² plots of weld were the most weedy parts of the whole garden and considering that each part of the garden was weeded exactly the same last year this is an indication that there is something about Weld that positively encourages weeds to grow. This is not too surprising when you remember that Weld is a pioneer plant of disturbed ground where it does not get much competition. However, although you would expect it to grow well where there is little or no competition, to then go a step further by saying it actually promotes the growth of other plants is a new thought for me.

There were a handful of surviving Weld plants nestled in the bare patches between tufts of grass but these were not looking so healthy. I was also expecting to see a lot of Weld seedlings in the bare patches as the Weld plants had been allowed to seed last year. A lot of that seed will have dropped on the plot but apart from 4 or 5 tiny seedlings there was no sign. This indicates that once again this pasture habitat is poor for Weld growing. I also believe that suggestions that Weld could be grown as a companion plant to barley are less feasible. Barley would most likely shade the small rosettes of Weld and kill them. The apparent ability to encourage weed growth may also make Weld difficult to grow even by itself.

Japanese Indigo (Persicaria tinctoria)

This had of course died at the end of last year during the first hard frosts but there were almost no weeds growing on this 1m² bed. This “weed suppressing” property of Japanese indigo matches our experience of growing this plant at home where we have noticed that the soil remains weed free long after the Japanese indigo has died, however, I was somewhat surprised to see the same thing happening here as the plants on this plot were unable to grow to a large size due to the drought last year. I had thought that the weed suppression was the result of the Indigo crowding out competition but it may be there is some other factor at work here – perhaps the plants produce a weed suppressant chemical? We do not know if this has been reported in the science literature but In a brief enquiry on social media a few other growers also report a similar effect. The production of “Bioherbicides” is not an unusual occurence and Anne Barwick from Edible Landscapes London forwarded me a link to a very useful review of the subject, see Here

As Japanese Indigo is capable of producing around four times the yield of Woad I am beginning to think that despite its need for water and sensitivity to frost this plant may be more profitably grown in the UK, particularly on flat damp flood plains in the wetter West of the country. If the effect is real then Japanese indigo may then be slotted into the sort of long crop rotation that regenerative farmers are seeking. This might give a yield of indigo one year which would then clear the way for a different crop the following year without the use of herbicide sprays.

Coreopsis (Coreopsis tinctoria)

We grew quite a lovely patch of this hardy annual from seed last year and because it rarely if ever self-seeds in our experience I was rather surprised to see quite a few plants remaining. Some of these may possibly be survivors from last year but some were also clearly self-seeded.  This is a native grassland plant from the North American plains so perhaps it’s not so surprising to see it survive here, but I was expecting it to have been eaten by the myriad of slugs which thrive in this field! Seemingly against all odds here it is.

Dyers Chamomile (Cota tinctoria)

This was last year’s star performer, continuing to grow well despite the lack of watering or rain to produce a really good display of golden daisy-like flowers. It’s a native of Eurasia from Siberia to Iran and surrounding areas so probably very much adapted to hot dry summers and if our climate here continues to warm could be a likely candidate for growing commercially.

Now in April of the following year it continues to impress producing a thick mass of growth as it builds itself up for another season of flowering. Usually described as a “weak perennial” this plant invariably dies in the summer of its second year. However in our dye garden at home many of the plants have gone on to a third year as a result of the hot weather last year. I am more and more impressed with this plant particularly as it will self-seed.

Rubiaceae family plants

Other Plants

I was pleased to see that all the other perennial plants on the plot are doing well. Saw-wort (Serratula tinctoria), two species of Golden Rod (Solidago canadensis and Solidago speciosa), Tansy (Tanacetum vulgare) and Dyer’s Greenweed (Genista tinctoria).

For this year’s Groundswell 23 I hope to be expanding the plot a little and growing some other dye plants.

References

Allelochemicals as Bioherbicides — Present and Perspectives