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Mr. Smarty Plants - Non-native wedelia and dayflower in Lihue HI

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Thursday - September 03, 2009

From: Lihue, HI
Region: Hawaii
Topic: Non-Natives
Title: Non-native wedelia and dayflower in Lihue HI
Answered by: Barbara Medford

QUESTION:

I have wedelia as ground covering, day flower or commelinaceae takes over. What can I use or spray to rid myself of the day flower problem?

ANSWER:

That old devil "common names" has struck again, but this has to be the most confusing one yet. In our Native Plant Database, there is one member of the Wedelia genus, Wedelia texana (hairy wedelia) synonyms Wedelia hispida, Zexminia hispida. This plant is endemic to Texas, member of the Asteraceae family. Often called Zexminia, it is a small shrub, from 8 inches to 3 ft. tall, evergreen in southern parts of its range. Here are pictures from the University of Texas Archive of Central Texas Plants Pictures of Wedelia. Then we started hunting a little further for infomation on the plant, and found on the Internet material referred to as Wedelia paludosa, which is not in our Native Plant Database, but seems to be native to the tropical Americas. One of the first things we learned about that plant is how very invasive it is, how it loves lush, moist territory, like Hawaii. In particular, you might want to read the negative comments from this Dave's Garden Plant Files Wedelia paludosa. 

Just searching on the common name "wedelia" we found this website from the University of Florida Turfgrass Science by Dr. Phil Busey, where it was also named as a member of the family Asteraceae. and looked and sounded a lot like our Texas wedelia, except ours is adapted to the Edwards Plateau which is NOT a wet and lush environment. 

Hoping for more enlightenment on the two plants we're talking about, we went on to the genus Commelina, of which there are 7 species native to North America, but none to Hawaii. We chose Commelina erecta var. angustifolia (whitemouth dayflower) as example, because it is native to Texas, as well as 27 other states, and we are familiar with it. It is perennial, and blooms blue from March to October; we found no indication that it is considered invasive, but it is often considered a weed in Texas gardens.

So, here is our dilemma: At the Lady Bird Johnson Wildflower Center, we are committed to the use, propagation and protection of plants native not only to North America but to the area in which they are being grown. We are talking about two plants, neither of which is native to Hawaii, and you are asking us to give you elimination help with one of them. Our first thought is that the two plants apparently bloom a long time, much of it concurrent, and we think the yellow flowers of the Wedelia and the blue flowers of the dayflower would be rather attractive together. Second thought, you don't like the plant that is coming up? Pull it out, very direct, and much less environmental impact. 

But you asked for a spray. We recommend neither for nor again herbicides, so you will have to make your own decision on that. Dayflowers are in the plant class Liliopsida, or monocot. There are herbicides specifically for killing grassy weeds, also monocots, but we don't actually know if it would kill the dayflower. This article from the Seattle Times Before you begin spraying, know how weed killers do their job lays out the case for and against various kinds of weed killers.

Pictures of Wedelia paludosa from Google

From our Native Plant Image Gallery


Wedelia texana

Wedelia texana

Commelina erecta var. angustifolia

Commelina erecta var. angustifolia

 

 

 

 

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