Am I embarrassed? You better believe it! I was all set to write this article praising Blue Mistflower, Conoclinium coelestinum, as a wonderful winter blossom. However, after doing research I have come to realize that the plant we have been calling Blue Mistflower is really the non-native Ageratum houstonianum.
Conoclinium coelestinum on left and Ageratum houstonianum on right
These two plants look almost identical: clusters of blue flowers, similar coarse triangular leaves; they grow up to two feet tall. This illustrates the problem you run into when you rely on matching the plant with a picture. Further research is always a good idea. If I had done my homework, I would have realized that Conoclinium coelestinum spreads mostly from creeping rhizomes and the plant in the garden (and my yard) doesn't have rhizomes. I would also have seen that the Ageratum has the reputation for reseeding itself to the point where it can become a pest, exactly like the plant in the garden.
Anyone who has "Blue Mistflower" in their yard, especially if you might have gotten it from me, check for rhizomes. If you find no rhizomes and want to get the native Conoclinium coelestinum, be aware this plant likes moist soil and does not do as well in dry areas.
UPDATE: We were able to successfully trade out our non-nativeAgeratum houstonianum for the native Conoclinium coelestinum! Our Blue Mistflower is now the real thing.
Wonder how to pronounce these scientific names? Go to http://www.beedictionary.com/meaning/Conoclinium_coelestinumand http://www.beedictionary.com/meaning/Ageratum_houstonianumMake sure your sound is on and click the speaker symbol..
References:
Online Atlas of Florida Vascular Plants, Conoclinium coelestinum http://www.florida.plantatlas.usf.edu/Plant.aspx?id=935
Online Atlas of Florida Vascular Plants, Ageratum houstonianum http://www.florida.plantatlas.usf.edu/Plant.aspx?id=286
Native for your Neighborhood, Blue Mistflower http://www.regionalconservation.org/beta/nfyn/plantdetail.asp?tx=Conocoel
Floridata, Conoclinium coelestinum, http://www.floridata.com/ref/c/cono_coe.cfm
Floridata, Ageratum houstonianum, http://www.floridata.com/ref/a/ager_hou.cfm