Archive
Wool Aliens
20/11/2025
No, I am not talking about knitted little green men! I first came across this term during field work research for my doctorate on a lowland heath, and was reminded of it recently during a Worcestershire ramble along the margins of some disturbed ground near the River Severn. There I spotted a plant I had not seen before which turned out to be green nightshade (pictured), a known wool alien. (It is a neophyte and not native to Britain[1].)
In botany, plants are termed wool aliens when their appearance at a site is a result of using or processing wool in one way or another and people transporting it. To aid their dispersal far and wide, many plants have evolved sticky hairs, hooks and burs on their seeds and propagules through natural selection. These attach themselves readily to a sheep before it is sheered, then travel with the wool after sheering to somewhere that the wool is processed or used, often far away. Ultimately, woollen mills may discard wastes locally or they may be used as mulches or soil improvers on agricultural land or orchards where seeds can germinate. No doubt this was the case on the crop field margin where I saw the green nightshade.
[1] Such species are also known as adventives, i.e. not native and not fully established (although may be locally naturalised).
The occurrence of wool aliens increased greatly in the nineteenth century when Britain became the largest importer of raw wool in the world, especially from New Zealand, Australia, and South Africa. With the wool came dozens of plant species. An early census of wool aliens in Britain by J. E. Lousley can be found in the archives of the Botanical Society of the British Isles[1]. There are many such plants to look out for, particularly among the nightshades, like S. nitidibaccatum illustrated in this note, as well as in families such as the brassicas, amaranths, daisies, geraniums and grasses as well as many others. Some have become rather invasive such as the pirri-pirri-bur Acaena novae-zelandiae and it is still important to be aware of the consequences for native biodiversity from introduced alien plants.
Betts Ecology are always keen to have records of unusual plants. Do email us of anything interesting you find, with a photo and details of its location.
[1] https://archive.bsbi.org.uk › Proc4p221.pdf
