It's Virginia dayflower, Commelina virginica.

Neil,

How come not Asiatic Dayflower, Commelina communis, the weedy non-native? The picture I found of virginica had a third blue lower "petal," like a bottom lip. I didn't know it, but there's a lot of other Commelinas out there too.

David

David -- I think you're right.

Neil,

Actually, now I'm not completely sure. I know greenpointmary's picture looks just like the Asiatic Dayflower, C. communis, that grows all over here. But other species look similar, and the internet pictures of other species I've looked at seem to vary a lot (including in number of petals), suggesting inacurracy in the labeling of pictures. My field guides are not at hand, so I'll have to double check later; but my guess is C. communis.

It looked like a very common weed to me, too, and the first common weeds I learned were Pennsylvania smartweed and Asian dayflower, so naturally I searched for "Pennsylvania dayflower" and came up with a page discussing Virginia dayflower in Pennsylvania, so I said to myself, "Of course, idiot, Virginia dayflower." I think when I first really encountered it years ago, it may have been in tradescantia rather than commelina, and neither the common nor scientific name stuck all that well.

I think it's the non-native asiatic dayflower. It sure looks exactly like the thing that I'm fighting here. April

I guess one person's weed is another person's flower! Thanks for the I.D.!

Mary,

If you've follow this forum for a while, you will have the opportunity tio read many discussions about definitions: weed, invasive, wildflower, native, introduced. Fascinating stuff to me, but these discussions often get compliated (and sometimes heated).

While some think that a weed is just 'a flower out of place', the term 'weed' refers to plant that tend to colonize disturbed habitats -- which by definition includes all yards and gardens. It's not about appearance: a beautiful flowering plant can be a terrible weed.

If you think of it this way, it doesn't matter whether your plant is the native or non-native dayflower, it is weedy if it behaves like a weed. The non-native dayflower is definitely weedy (but not a major problem, to my knowledge). I don't know about the native species, but many there are many well-behaved native species that are closely related to non-native weeds. A good example is the native honeyuckles vs the Asian honeysuckles.

I can surely accept how something can be despised in the garden or yard. I let some bermuda grass get out of hand and it took over a bed in what seemd like a day! Now, if it was a good-looking weed, I wouldn't mind, as long as it wasn't strangling other plants. We have a ton of violets in the backyard, right where this dayflower is, which is perfectly fine by me. I know some people hate these violets because of the desire and effort to have a "grass only" yard.

Anyway, I found a guide book and am pretty sure it is of the Asiatic variety. Definitley not Virginian, although it also looks like it could be the slender dayflower variety, too. It isn't damp at all where this dayflower is growing, since we haven't had rain in ages. Also, since the asiatic dayflower is classified as an annual, how would it have gotten there? Lots of questions- I'm a newbie!