Variety Trials 5: Results after 2 years

It is now close to 2 years since we sowed the first seeds of our variety trials in April 2024, and almost one and a half years since my last report, there is therefore much to write about.

 Woad 

Starting with the woad, we left off having made our cold-water extractions to test colour content differences between the 21 varieties. The results were interesting on 3 points; firstly a few varieties gave very good colour from the July harvest, but much poorer results from the August harvest. Second, productivity in terms of biomass harvested appears to correlate with paler colour samples, thereby begging the question whether some varieties would produce more pigment per acre even it produces less pigment per kilo of leaf. 

Above: Picture of woad samples organised by bluest to least blue from the August samples. Red numbers indicate good colour anomaly between harvests. Green numbers are most productive in July and Purple most productive in August

The third interesting results came from the silk samples we sent for laboratory analysis, the readings of which appear to indicate a lessening of dye content over 3 consecutive harvests - July, August and September - in the Isatis tinctoria. Whereas the Isatis indigotica samples appear to have a tendency to increase in ‘blueness’ as the season progressed.

By the end of the growing season 2025 and with our productivity, dye content and suitability for seed production in the Irish climate results for the woad in hand, we have decided on 2 strategies going forward.

The first is to develop what is commonly known as an ‘Evolutionary Population’, where we grouped the 5 best varieties in a new location in order to enable them to cross pollinate. Thereby, creating a very large genetic pool, that will be a new, resilient and adaptable population, from which new varieties can be bred. 

The second strategy we are pursuing involves developing and improving variety 23, which consistently gave us the best dye results in our initial trials. This strategy has involved further researching the provenance and history of this specific variety, in order to obtain seed of the same variety from different sources. This is to enable us to recombine them as a variety, to reinvigorate it and negate any possible inbreeding depression due to possible genetic bottle necks, in this varieties' production and conservation over the years. Our research yielded 3 separate sources of seed guaranteed to be from the same original source. 

It is interesting to note that this variety came from France, which has such a long history of woad production and dyeing practices. 

To achieve the improvement of this variety we are growing larger amounts of plants, in order to select for health and advantageous phenotypic traits, over a number of generations.

We are carrying out this next phase in our new garden, where we can grow larger quantities. From these larger grow outs we are also able to experiment with scaling up pigment extraction.

Weld

The initial phase of the Weld trials finally yielded results this summer, once the true biennial variety went to flower and we were finally able to harvest and extract colour from all 7 varieties. We carried out an initial extraction to compare each of the varieties, but had to extract them in 2 lots, which means that these results could not be conclusive. However, it gave us preliminary results.

Weld varieties dye samples

To obtain reliable results, we sent samples of the dried material to be tested under laboratory conditions. This revealed that all the annual weld varieties yielded good dye content, with a couple of them yielding better than average colour.  

In the meantime, we also grew a larger population of the annual weld in 2025, and were very happy to see that this variety was very productive in flower spikes for dye material, as well as producing good quality seed.

Biennial Weld in flower                            Annual Weld in flower

Our goal with the weld, will be to make both the annual and the biennial seed available in our shop, while continuing research on the annual variety, by having it grown at more southern latitudes, to see whether it is a biennial there.

Persicaria

The goals of this research have been to reveal productivity, colour content and suitability for seed production in the Irish climate. While it has proven very useful for the woad and the weld, both of which produce seed easily in the Irish climate. The last goal has proven essential for Persicaria, because it has become clear that only the earliest flowering variety is suitable for producing seed in Ireland outdoors. Out of the 7 varieties we tested, there was a significant 6 week difference in the appearance of the first flower. The first flower on the earliest flowering variety opened on the 13^th September, whereas the latest flowering variety only started flowering on the 22^nd of October. This was very important information, as even the earliest flowering variety will not reliably produce seed every year; depending on the first frost on any given year.

Persicaria 05 seed crop in the new garden August 2025 

I grew the latest flowering variety in the tunnel this growing season because it appears the seed longevity of this variety is considerably longer than most other varieties. However, I was rather astonished that even in the tunnel, it did not produce any seed, even though I managed to protect it from the early frosts. Though it produced plenty of flowers, it produced no seed at all. This leads me to believe that, because it flowers so late in the year, there are no longer enough of the correct pollinators active, to achieve fertilisation. However, despite the early frosts, we managed to save some seed from the earliest flowering variety outdoors, and this is available in our shop, if in small quantities only. 

A great coincidence from the persicaria varieties tested, number 05 in the picture above gives both the best colour content as well as being the earliest flowering variety, which makes it suitable for seed production in the Irish climate.

Madder

For the Madder, the biggest difference is still the growing habit of clumping or spreading. After 2 years, with the second year of that growth being in the new garden, there are only 3 varieties that are showing the clumping habit. Two of the three clumping varieties have considerable variability for this trait within the variety, while 1 seems most reliable.

While most of the plants flowered in their first year, there was nearly no seed produced by any of the varieties. This year, there was significantly more healthy large seed produced by some of the varieties, though; similar to the clumping habit there appears to be significant variability both between and within varieties. I expect clearer results for these traits by the end of next year, as well as finally being able to harvest the roots, through which we will finally be able to evaluate this trial for productivity and colour content.

Madder varieties before transplanting                 Madder varieties in the new garden