Crescent cup liverwort is a fairly common liverwort species in Oregon nurseries. I've observed this plant in several nurseries. However, it is much less common than the more familiar Marchantia polymorpha. Of all the liverwort I've seen, L. cruciata makes up less than 2% (just my personal observation). I don't consider this to be an economically important weed, nonetheless, it does occur in container production so proper identification is useful..
The conditions in which it grows are similar to Marchantia. According to Sven Svenson, chemical control of this species is easier than Marchantia, which might explain why I see it less often.
I have only observed the thallus of this species, I have never seen its sex organs (mostly because I rarely see it). The thallus is readily distinguishable from Marchantia.
|Lunularia cruciata||Marchantia polymorpha|
|L. cruciata forms much smaller thalli (leaf structures) than Marchantia. In the image above, Osmocote prills serve as a visual scale. Notice that this species co-habitates with pearlwort (Sagina procumbens), which is to say it prefers moist substrates with high fertility.||Thalli of Marchantia are much larger than that of L. cruciata, growing an inch or more in diameter.|
|Gemmae cups of L. cruciata are crescent shaped (hence its common name). In this image, and the one for Marchantia, notice the little spherical bodies inside the gemmae cups. These are the gemmae, which are diaspore, clonal fragments that splash from the mother plant to form an new plant.||Gemmae of Marchantia are circular and complete, looking like little volcanoes.|
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