Liverworts along with mosses, belong to a group of plants known as the Bryophytes and grow on the surface of soil where the drainage is poor. There are about 289 species found in Britain. Marchantia polymorpha shown here, is very common in gardens and greenhouses. Evidence from spores from about 470 million years ago suggests that similar life forms to the liverworts may have been the first 'plant' life to establish out of water as algae moved onto land, which shows how relatively primitive they are in structure. There are no roots, no organised tissues to conduct water and nutrients nor stomata to regulate water loss; the waxy surface gives some protection, but in dry conditions the whole plant will shrivel.
There are two types of liverwort, the Leafy and the Thallose. Leafy liverworts have tiny, overlapping scale-like "leaves" arranged along a very fine stem and some can resemble a miniture fern.
The thick dark green, flattened structure of the Thallose type has upward-facing male reproductive structures like toadstools called antheridial stalks and female, parasol-shaped hoods borne on a stalk (archegonial stalks), resembling a miniature palm tree. There can be dioicous species with male and female parts on separate plants or monoicous species with the sexual parts on different branches of the same plant. When ripe the elevated capsules on the undersides of the female structures burst open and if conditions are favourable a new plant will develop from spores that are released.
There are fine fibrous root-like structures called rhizoids about 5mm long, in a row below the midrib on each thallus, these are for anchorage and water uptake, and make removal quite difficult. Because of their appearance, it was once believed that following the Doctrine of Signatures that liverworts could cure diseases of the liver, hence the name.
If there is no mulch, use a hoe to keep the surface soil loose to about 3 to 4 cm deep. When a large area is covered the best solution is to slice off the Liverwort and apply fresh mulch.
Glyphosate will kill it, but should be applied with a few drops of detergent in the water to try to penetrate the waxy surface of the thallus. However, if it has been present for some time there will be gemmae present and it will return. Some say that using a weedkiller encourages Liverworts and Mosses to grow, but this could be that having removed all of the competition the ground is open for them to invade. Also if the ground has not been disturbed by uprooting the weeds the smooth compacted surface is more conducive to their establishment.
Liverwort thalli with sexual and asexual reproductive structures.
The small, green, seed-like gemmae falling out of the cupule.
See also the monographs on Dog Lichen, Blue-green Algae and Moss which may be found in similar locations.
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