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Sunday - July 20, 2008

From: Houston, TX
Region: Southwest
Topic: Container Gardens
Title: Failure of potted verbena to bloom
Answered by: Barbara Medford


I have a trailing purple verbena that won't bloom. It is in a container, not in the ground, and gets lots of sun. What is the problem?


In our Native Plant Database, there are 36 species with the name "verbena" in the name of the plant, most members of the genus Glandularia. Probably the most-used native verbena is Glandularia bipinnatifida (Dakota mock vervain). We are pretty sure that what you have is some sort of a hybrid, with different colors, as that is what is usually available in commercial nurseries. Since we don't know, and you were probably not given any indication, what hybrid this would be, we can only deal with your question on a general basis. This website from GardenGuides.com Verbena can give you some more care information, regardless of the species. In cooler climates, verbena are considered annuals, but in Houston, you should be able to get it to perennialize. You said it was in a container, so you need to make sure the container drains very well. The verbena needs moist soil until it is pretty well-established, but cannot tolerate soil that does not drain well, and may develop disease because of the poor drainage. The native verbena mentioned above blooms from March to October. Although our webpage on the verbena says it needs part shade, which we define as 2-6 hours of sun a day, other websites say that verbena needs full sun, up to 8 to 10 hours a day of sun. A plant that needs lots of sun to bloom is not going to do well in a more shaded location. If blooms seem to slow during the summer, you might trim the whole plant back by about 1/4, and hopefully it will recover its vigor and bloom again. Dedheading is important on this plant but, again, just trimming across the top to take off spent blooms should suffice, instead of snipping off each individual blossom. If your plant has lush foliage and no flowers, we suspect the plant food you are giving it is heavy on nitrogen, which promotes green leaves. Switch to one that has a higher phosphorus content, the number in the middle of fertilizer designations, and see if that will inspire your plant to bloom.


From the Image Gallery

Prairie verbena
Glandularia bipinnatifida

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