Pilea pumila (Dwarf Clearweed)
|Also known as:||Canadian Clearweed|
|Habitat:||part shade, shade; moist shaded woods, wetlands, wooded shores|
|Bloom season:||July - September|
|Plant height:||4 to 20 inches|
|Wetland Indicator Status:||GP: FAC MW: FACW NCNE: FACW|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Separate male and female flowers, both small and indistinct, green to pale yellow and densely packed in horizontally spreading, irregular panicles about 1 inch long arising from leaf axils in the upper half of the plant.
Leaves and stems:
Leaves are opposite, elliptical to egg-shaped, 1 to 5 inches long, the tip pointed, the base rounded to wedge-shaped, on a stalk about half as long as the leaf blade. Leaves are thin and somewhat translucent with three prominent veins from the base. Surfaces are shiny with scattered short hairs on the upper surface. Edges are toothed, sometimes double toothed. Stems are sometimes branched but usually not, very fleshy and translucent, somewhat squarish, very smooth and shiny.
Fruit is a flattened, teardrop shaped seed, up to 1/16 inch long and about half as wide as long.
Surfaces are patterned with random dark purple to black spots against light green, but rather variable in the amount of green to black.
Pilea pumila is one of two native clearweeds in Minnesota, the other is Black-fruited Clearweed (Pilea fontana). They are nearly impossible to distinguish but for the size and color of their fruit (achenes), and only when fruit is present. As described, P. pumila's fruit is smaller and proportionately narrower, with scattered dark pigment spots against light green. P. fontana's achene is larger, proportionately broader, solidly dark pigmented but for a narrow green edging. Typically the difference is distinguishable with the naked eye with the larger, darker fruit of P. fontana standing out while still in the panicle, though some more darkly pigmented P. pumila may be more easily confirmed by collecting some fruit into the palm of your hand for closer inspection.
Some references note differences in the degree of translucency between the two species, but these are not reliable traits to distinguish them in the field. Even when the two are side by side the differences are too subtle for a positive ID. Of note is that Flora of North America states the two are not often encountered together, even though their habitats and distribution ranges overlap considerably. The leaves of the two Pilea species are similar to other members of the Nettle family, most closely to False Nettle (Boehmeria cylindrica), which has more spike-like flower clusters and leaves more finely serrated with more than 3 prominent veins scattered along the midrib, and Wood Nettle (Laportea canadensis), which has stinging hairs and is a considerably larger plant.
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Photos courtesy Peter M. Dziuk taken in a private wooded garden in Anoka County and at Westwood Nature Center in Hennepin County. Seed photos courtesy Rick Haug.
Have you seen this plant in Minnesota, or have any other comments about it?
on: 2013-09-06 19:33:13
This is the first year I have noticed this clearweed in our garden and flower beds in the back yard.
on: 2014-09-01 16:01:37
We live in the Minnetonka area. This is the first year I've become aware of clearweed. I first removed a lot of buckthorn for several years, then garlic mustard moved in and I tried to control that. Now clear weed has covered the understory of the back woods previously covered by the two previous weeds. Am I winning or losing?
on: 2014-09-01 20:02:57
Bill, chances are clearweed was in your woods before the invasives arrived. It is native, after all, and moist woods is suitable habitat.
on: 2015-08-29 02:23:41
Thanks for the photos. I'd been wondering what this bright green plant was that soon carpeted the edges of trails that were widened or where we had removed dense garlic mustard stands.
on: 2017-07-22 15:18:15
We are getting tons of this the last few years. We have a very shady lot and it is running rampant in our flower beds...even in our lawn and areas where we're trying to cultivate moss. How can we get rid of it?
on: 2017-09-03 19:37:47
I too found that this plant seems to profit from the eradication of garlic mustard. It must be that the allelopathic effects from the garlic mustard at least benefit this one native species. It wasn't very common before the garlic mustard invasion, but after eliminating the garlic mustard, it now totally blankets the forest floor in my back yard. Glad to discover it's native at least! Hopefully the native microbiota in the soil will recover and other native species will return.
on: 2018-07-17 09:18:17
Just found this in my yard for the first time. It's also popping up for me in an area I cleared of garlic mustard and other noxious weeds about 3-4 years ago. Right next to my very bold (i.e., it picked a rather sunny spot) Jack in the Pulpit.
on: 2018-07-25 13:50:52
I've just started noticing clearweed, and its all over the place, mostly in overgrown areas. (And, actually, pretty lovely.) So, I wonder, why would this be called "native" since both the weediness and the rapid incursion speak rather loudly of "exotic".
on: 2018-09-24 01:35:43
There are thousands of Garlic Mustard plants throughout the wooded area behind my house leading to Bassett Creek. Have tried to eradicate it, but fear I'm loosing that battle. Now my 2/3 acre of perennial gardens are being overrun with what I see is identified as Clearweed. It seems no amount of pulling the plant keeps it away! How can it be controlled?
on: 2018-12-31 02:31:15
In damp wooded areas along the St. Louis River in Duluth.
on: 2019-06-20 10:12:57
I am a eco Dyer. I would like to know if clearweed is a plant that I can extract dye from.
on: 2019-07-12 15:00:24
Moi aussie! I'm in follow up stages of clearing a rather thick buckthorn infestation and battling a garlic mustard threat on 3+ acres of mostly oak now open woodland. There is lots of clear weed and hog peanut on recently bare ground.
My aesthetic is quite natural and, as long as I needn't concern myself about a new unnatural imbalance manifesting in a clear weed forest, I think the bright yellow green makes for a rather good looking ground cover. It compliments the darker and cooler greens of other plants around it quite well. Anyone have any idea where succession may lead?
on: 2019-08-02 15:48:54
Comforting to learn our sequential years of battling garlic mustard followed now by clearweed are not a unique experience. Not so comforting to read nothing telling me what to battle it with other than old fashioned pulling! At least it is shallow rooted and thornless.
on: 2019-11-04 17:17:56
Popped in en masse for first time this year in a very large monarch habitat native garden. Perhaps due to wet winter/spring/summer. Never have seen it before. Wondering if it is a host plant like other nettles, and if it is necessary to "battle" it, if it doesn't impede other natives from emerging.
on: 2020-08-31 11:01:03
Have been trying to eradicate Pilea Pumila (Clearweed) for several years now. This year- 2020 - it seems to be especially prolific. It's easy to pull out but you are forever weeding. Any suggestions as to how to get rid of it?
on: 2020-08-31 18:02:16
Karin, I have it in my yard, too. It just appeared under the deck a few years ago and seems pretty happy there. It's an annual so reproduces only by seed and you may have a seed bank to contend with for some years yet, but it's easy to pull up if you don't want it.