I return from many of my walks with pockets full of lichen windfall. One of the common finds under trees is two slightly different species of Hypogymnia, a good dye lichen.
Lichen windfall is perfect for dyeing, since it does no damage to just pick up the fallen lichens. I’m therefore writing a small series of posts on the different species of lichens typically found in windfall, and I’ve already written about Ramalina fastigiata.
This time, I’ll have a look at Hypogymnia physodes and Hypogymnia tubulosa, two common species that are closely related (that’s why part of the name is the same). Also, they do look alike – both are grey-green and foliose (flattened, leaf-like). Hypogymnia physodes, here seen covering a small branch, has flat lobes, sometimes with soredia on the outer part. Soredia is one of the way that lichens can reproduce, and break through the surface in lots of little dots, making the surface look grainy or powdery. In Hypogymnia species, the soredia are found on the bottom side, which folds up on the tips of the lobes, making the grainy lower surface visible:
Hypogymnia tubulosa looks a lot like Hypogymnia physodes, but has hollow lobes. In the right side of the image below, the hollowness is visible since I cut one of the lobes:
Both species are very common, and grow in many places, including on trees, stones, and wooden surfaces. They like growing on acidic substrates, and Dobson’s “Lichens, An Illustrated Guide to the British and Irish Species” mentions that Hypogymnia physodes is among the species least sensitive to sulfur dioxide pollution. Hypogymnia tubulosa is a bit more sensitive.
The dye content sometimes differs a lot even for species that are otherwise very similar. So I decided to test if the two species give the same color.
I used unmordanted yarn, since lichen colors are substantive. I made one dyebath with 9 g of Hypogymnia tubulosa, and put a 12-gram skein of Fenris (pure wool) and a 5-gram skein of Bestla (merino-silk) in. Another dyebath was 15 g of Hypogymnia physodes, and two 12-gram Fenris skeins and one 5-gram Bestla skein went into that one. So half the weight of lichen compared to fiber in both cases. I modified one of the Fenris skeins in an iron afterbath.
Both lichens give the same color – a fine, dusty yellow, the completely expected shade from bwm lichens. So in conclusion, no reason to sort Hypogymnia physodes and tubulosa. The merino-silk takes the color a little less well than the pure wool, and an iron afterbath does significantly darken/sadden the color at turn it green.