Asiatic Day Flower
Commelina communis L. is the correct and accepted scientific name for the Day Flower. It was named and described as such by Carl von Linnaeus in the first edition of Species Plantarum in 1753.
Accepted infraspecific names: Commelina communis var. communis, Commelina communis var. ludens (Miq.) C.B.Clarke
The genus, Commelina Plum. ex L., was described by Carl von Linnaeus in the first edition of Species Plantarum in 1753. It was first named by Charles Plumier then later described by Mr. Linnaeus. Plants of the World Online list 195 accepted species in the Commelina genus as of when I am updating this page on 1-26-20. That number could change. A few months earlier there were 200.
The above map from Plants of the World Online, by permission, shows where Commelina communis is native in green and purple where it has been introduced. The species could be in other areas but may not have been reported. The USDA Plants Database shows a similar map of the United States but also includes the state of Washington.
Please check the links at the bottom of the page for further reading and positive ID.
2019 was a great year for identifying wildflowers on the farm. I took photos of Dayflowers in 2018 but I was just barely getting started identifying the wildflowers here. In 2019, I decided to ID as many as I could but I got fairly busy at a friend’s farm. It wasn’t until the end of August that I took the first photos of Commelina erecta and I didn’t see any C. communis until September 1.
The Commelina erecta were in a very large colony along kind of ditch where the pasture drains into that leads to the pond. At first, I was checking their flowers sterile anthers for reddish-brown dots which is a characteristic of C. communis. There was a strange problem… The spath-like bracts the flowers emerge from of Commelina erecta are supposed to be closed while the bracts of C. communis are supposed to be open. However, all the flowers in this colony were open instead of closed… The flowers had light blue petals and no reddish-brown dots like C. erects… So why were their bracts open instead of closed?
Finally, on September 1 as I was leaving the area, I looked down on the left side of where I went in and spotted a few plants with darker blue flowers. I took a closer look and low and behold the sterile anthers had reddish-brown spots. I had found Commelina communis! But, something was weird! Their bracts were fused together where they should have been open! I thought maybe I had them backward even though I was sure I knew what I was looking for. After I took several photos, I went back inside to check. Sure enough, Commelina communis are supposed to have open bracts. That is one of the feature characteristics that sperate it from C. erects, besides having the reddish-brown spots.
Flowers emerge from a heart-shaped bract called a spathe (spathelike bract) which is attached to the stem by a peduncle. One to three flowers will be produced inside the spathe. Normally the flowers will open in succession but I have seen two at the same with the C. erecta.
The two upper petals of C. communis are a darker, true-blue.
The above photo shows the difference between Comellina communis on the left and Commelina erecta on the right. The three sterile anthers AND the three lower fertile anthers of the C. communis have reddish-brown spots.
The above photo shows the closed bracts on the C. communis on the left and open bracts of the C. erecta on the right. C. communis bracts are supposed to be open and C. erecta bracts are supposed to be closed… Hmmm…
On September 18 I noticed a few Commelina communis near the swampy area in the southeast corner of the farm. These flowers had open bracts like they are supposed to. There were no other Commelina species in the area.
I have read that Commelina species compete for pollinators so it is rare two species grow in the same area. Although there are both C. communis and C. erecta growing fairly close to one another in the one lot, they are not growing among each other. I am wondering is they have adapted in that area and somehow C. erecta thinks open bracts attracts more pollinators and C. communis thinks it is better off with closed bracts. Hmmm…
Good photo of the three sterile anthers and three fertile anthers with the reddish-brown spots on the staminodes.
According to Plants of the World Online, besides Commelina communis, there are two accepted infraspecific names (varieties). I didn’t see anything online that talks about C. communis var. communis or C. communis var. ludens. I thought maybe one of them may have open bracts rather than closed. So, I decided to go back to the library and get Steyermark’s Flora of Missouri AGAIN to see if there was any information.
Above photo showing two spent flowers and visible ovaries which will turn into fruit that produce the seeds.
While I cannot quote what Steyermark’s says, I can get close. 🙂 The interesting thing it says is that Commelina communis has NO reddish-brown spots on the staminodes. Ummm… How can that be when every website says that the spots are one of the distinguishing features and I have them right in front of my face?
Like a couple of babies…
I never really understood how a species can have a variety with the same name such as Commelina communis var communis. Steyermark’s refers to this variety as the “common var. communis” and says their upper petals are 10-15 mm long, has glabrous leaf sheaths, its anthers, false anthers and staminodes are all yellow. Hmmm… Commelina communis has basically the same description with 8-16 mm upper petals. Oh yeah, it says their flowers are blue OR less commonly purple…
As far as the other variety, Commelina communis var. ludens, is concerned… Steyermark’s says this variety has “purple” upper petals, 8-10 mm long, PLUS the anthers and false anthers have purplish-brown spots in the middle of the staminodes.
In 2020I will take more photos of the Commelina communis. I was so carried away taking flower photos I didn’t get any of their leaves and stems but I can give a basic description.
Commelina communis is considered an annual plant with slender, fibrous roots. Stems are fairly erect until they get longer then they become descending or decumbent (sprawly) and they can root at the leaf nodes. The sheaths on the leaf nodes can be glaucous and have white hairs near the tips. Leaves are kind of lance-shaped (lanceolate) to narrowly ovate. The spathelike bracts the flowers emerge from are “supposed to be” open, like a taco. They are folded so the lower edge is actually the midrib. If they were unfolded they would be heart-shaped.
The flowers… Well, as I mentioned, they are normally blue and purple is quite rare. All websites say one of the distinguishing features of “the species” is the reddish-brown spots in the center of the staminodes on the anthers and false anthers. But, in light of what Steyermark’s says, that may not always be the case. So, we look to the spathelike bracts which are supposed to be open the entire length. But, as with plants here on my farm, that is not always the case either. GEEZ!
So, for argument’s sake and to make it simple, let’s assume that Commelina communis have two upper blue petals and a smaller white lower petal, reddish-brown spots on the staminodes of the anthers and false anthers, and the spathelike bracts are supposed to be open the entire length.
If you find flowers that are purple, congratulations and you should report them. If you find flowers that are light blue with no dark spots and fused spathelike bracts, it is likely you have found Commelina erecta. If you have found Dayflowers with three blue petals, they are likely Commelina caroliniana, Commelina diffusa, or perhaps Commelina virginica…
I have enjoyed photographing and learning about the many wildflowers growing on the farm and other areas. I have grown over 500 different plants and most have pages listed on the right side of the blog. I am not an expert, botanist, or horticulturalist. I just like growing, photographing and writing about my experience. I rely on several websites for ID and a horticulturalist I contact if I cannot figure them out. Wildflowers can be somewhat variable from location to location, so sometimes it gets a bit confusing. If you see I have made an error, please let me know so I can correct what I have written.
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