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 Old World diamond-flower, Hedyotis corymbosa

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Old World Diamondflower

Philip Busey

The little weed that could

Diamondflower is a little weed that is frequently misnamed.  Some people call this plant doveweed, but the two couldn't be farther apart biologically.  While doveweed is a monocot, diamondflower is a dicot, thus a broadleaf weed, and a member of the Rubiaceae.  The same family includes coffee as well as several other difficult turf weeds such as Florida buttonweed.
















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Old World diamondflower Hedyotis corymbosa (Oldenlandia) close up
Branch of Old World diamondflower.  The < 2 mm long flowers are somewhat campanulate, though the petals are not fused.  This image was taken from a scan.

Old World diamondflower was probably increasing in abundance on Florida golf courses during the late 1990s, although the plant was first pointed out to me in 1976 by the late Dr. Ev Burt, weed scientist at University of Florida - Fort Lauderdale.  My first attempt to key out this weed landed me in the genus Oldenlandia, the same genus in which Linnaeus placed it when he described it in Species Plantarum in 1753.  Since then, it has been transferred to the genus Hedyotis and its full handle is Hedyotis corymbosa.

Asked to describe their fall problem weed, most golf superintendents remark on the small whitish flowers, and the tenacity of a short, patchy, ground-hugging weed.  There may be a few other broadleaf weeds that come into play in the winter, such as the pigweeds, or Amaranthus, and even bur clover, but diamondflower is among the more important.  The Rubiaceae, or coffee family, has several distinctive features, such as interpetiolar stipules.  Looking at the point of attachment of the opposite leaves, there is a cup-like collar extending around the stem from one leaf to the other.  This cup-like structure is the fused stipules of the opposite leaves.

Old World diamondflower forms weak adventitious roots along the stolon nodes, but it is primarily taprooted.  This makes it relatively easy to pull up. In fact, the larger plants can be scooped up by hand or rolled into a small bale, then yanked up from the taproot.  A single acre can have hundreds of individual plants of various sizes, which could make hand pulling time intensive.  The seeds are relatively small, so that the plant can potentially repopulate an area.  It is not known if this can occur during a single season.

Unfortunately there is no known herbicide which will control Old World diamondflower.   Apparently the phenoxy herbicides are not effective.  New herbicides, including experimental products and recent registrations should be studied.

Other information on distribution and possible medicinal properties

Disclaimer:  This is a  preliminary report of research in progress, and may not be used for management decisions, including the use of particular products.  The information is made available to stimulate discussion and careful observation among turfgrass managers, chemical company representatives, and others interested, regarding possible future directions for weed control research.

Hedyotis corymbosa is found in most counties in Florida
http://www.usf.edu/~isb/projects/atlas/maps/hedycory.gif

It is also a weed in east Texas and western Australia.

Chemical properties in Hedyotis have been shown to reduce tumors:
http://www.cancerprev.org/Meetings/1998/Abstracts/PrimaryPrevention/520.shtml

In Taiwan it is reported to have anti-inflammatory and liver-protective properties:
http://www.ccmp.gov.tw/5e/81-4-7e.htm

It is used in Ayurvedic medicine:
http://www.ayush.com/herbs.html

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