Thursday, May 2, 2013

Plant Story: The dreadful field bindweed

sprouting field bindweed
Sprouting field bindweed
April 28, 2013. Bindweed!  The bindweed in my yard is up!

field bindweed, Convolvulus arvensis
field bindweed, Convolvulus arvensis
   Bindweed is the bane of gardeners along the Rocky Mountain Front Range, more than crab grass, more than dandelions. 

     Field bindweed, Convolulus arvensis, is a deep-rooted perennial vine. 

      It spreads. 

      It comes back after being pulled up. 

    I wage a war against bindweed all summer, every summer. No bindweed flowers are allowed to produce seeds in my yard. And I pull up the vines when I see them. Over and over.

    I want to believe that I have made some progress. Only two or three small plants remain in my front yard. The back yard has a lot farther to go to be bindweed-free, however, and a quick look on the 28th found dozens of new shoots just breaking the soil. It snowed all day May 1, perhaps 10” and the snow was still deep on May 2. The cold will slow them, but the war with the bindweed is on again for 2013.
snow May 1
May 1 snow

    I try to give every plant its due. Generally I let one grow somewhere in my yard and weed out all the rest of the seedlings of that species. For example, one maple seedling is turning into a nice tree, one mullein is allowed in a secluded corner, one invading sumac can have a spot by the fence. Not bindweed. After considering letting them decorate the wood pile, I decided that they could grow throughout the rest of Colorado, but not in my yard. 



    Field bindweed grows in very large numbers across the high plains of Colorado and adjacent states. Professor Jane Bock of the University of Colorado Boulder suggested that bindweed was actually Colorado’s state flower, since there was so much of it. Not really of course but there IS a lot of it.
Field of field bindweed
Field of field bindweed
   Bindweed is in the morning glory family, Convolvulaceae, along with morning glories such as heavenly blue and scarlet o’hara and the sweet potato. Actually, it might be better to say morning glories are in the bindweed family, because the family name, Convolvulaceae, is based on the genus of bindweed, Convolvulus. Convolvulus is from the Latin convolva, to twine around, as in the English convoluted. The second word, arvensis, means of cultivated fields. 
    Field bindweed is native around the Mediterranean but currently can be found all over the world, almost always as an unwelcome weed. In England, in 1633, Gerard wrote in his Herball, “...Bindweeds are not fit for medicine but are unprofitable weeds, and hurtfull unto each thing that groweth next unto them.” ( p. 864). The first record of field bindweed in North America was in 1739 in Virginia. It probably arrived in the ballast of ships but may have also been a contaminant of imported seeds.  

    For most of the next 100 years it was found here and there in North America but not seen as a problem. About 1800, the flowers were considered attractive and you could buy seeds for your garden. Field bindweed can be used as medicine: it has purgative properties and was considered helpful in healing wounds. 

    Often when a plant reaches distant shores, it arrives without the insects, fungi, bacteria and viruses that traditionally ate it. It will also have left behind small and large animals that considered it tasty. So in the new environment, it is less troubled by pests and grows better than it did at home. For many plants, a few more seeds per year surviving to grow into plants takes them from common to irritatingly common. Field bindweed is not so incredibly abundant in southern Europe.

   Field bindweed spread westward across the 1800s, probably moving with settlement. The first report in Kansas was in 1877. By 1900 it was in all the western states of the U.S. and across Canada. During the 20th century, its abundance increased. It is currently rated as a noxious weed in at least 22 states.

    Part of the reason field bindweed is so hated is that it is a vine. Vines grow from one plant to another in an agricultural field, tangling them. In this way bindweed is very like its relatives, the weedy morning glories (see blog on morning glories)

    Another reason field bindweed is hated is because it is a perennial that regrows from a deep taproot. The taproot sends out other roots (called rhizomes) at or below the soil surface. They easily run six feet (2 meters)--under rocks or logs or ground cover fabric. The rhizomes have been found at least as deep as 23 inches (60 cm) below soil surface, which is why pulling up a piece, even a big piece, is unlikely to eradicate it.  

     Like many other species in the morning glory family, they have single-day flowers. The flowers open as the morning warms up, wilt in the early afternoon. I can glance at my flower beds at breakfast and see no bindweed, and about 10 am, be horrified to see a dozen little white flowers. If I don’t go out before noon, the flowers are hard to find and pull off because they have wilted and are much less obvious. Pulling off flowers stops seed production. It only slows the spread of field bindweed--but it does slow it.

field bindweed, Convolvulus arvensis
field bindweed, Convolvulus arvensis flower
   As far as I can tell, bindweed flowers do not self-pollinate, but require an insect to carry pollen between flowers for seeds to form. The little flowers are attractive to a variety of local insects-- small native bees, honey bees, butterflies, moths--so the plants easily produce a lot of seeds. 

     Each flower makes one to four seeds, which means over a summer a single plant can easily make 25-300 seeds. A study in Texas, not worried about how many plants there were but rather what the potential for more seeds was, estimated that the plants produced 250 seeds per square yard (approximately a square meter).  
     
     Bindweed seeds have been shown to be able to germinate after 25 years buried in the soil. Stored in a lab in Belgium, bindweed seeds were alive and able to grow after 50 years. 

      Bindweed has impressive potential for spreading and for reappearing on a site where has not been seen for years.

   (We don’t know a great deal about how long seeds can last because, to know that, someone had to set a large number of seeds on a laboratory shelf or, better, bury them in the ground. Most projects last 3-10 years, most research laboratories change their focus every decade or so, and the working lives of botanists are 30-40 years. It is the rare person or laboratory who keeps track of seeds for decades and cares to come back every 10 years or so to plant the seeds to see if they are still able to germinate and grow. Field bindweed seeds may have greater longevity than has been reported.)

    Although it may have medicinal value, field bindweed is mildly toxic. When a pasture is overrun by bindweed, there is danger that livestock, particularly horses, will eat enough to poison themselves. That is another reason why bindweed is unpopular along the Front Range. 
silk dyed with bindweed
silk dyed
with bindweed
yarn dyed with bindweed
wool yarn dyed
with bindweed
  Last summer Spike (see her blog) and I found a positive use for field bindweed. It makes a nice strong yellow dye on wool and silk. Gathering enough leaves for a dyepot can really set back the local population. 

   I feel I may have maligned the plant. The flowers are pretty and success ought to be admired. The problem is--field bindweed could easily overwhelm my yard and I'd have very little except bindweed. The flowers aren't that pretty! And so, weeding out bindweed shoots and removing every flower I see will continue this summer and beyond.

Comments and corrections welcome!

References
Austin, D. F. 2000. Bindweed (Convolvulus arvensis, Convolvulaceae) in North America--from medicine to menace. Journal of the Torrey Botanical Society. 127 (2): 172-177. 
Coombes, A. J. 1985. Dictionary of plant names. Timber Press, Portland OR. 
Gerard. J. 1975. The herbal or general history of plants. originally published 1633. Dover Publications, New York.
Todd, F. G., F. R. Stermitz, P. Schultheis, A. P. Knight and J. Traub-Dargatz. 1995. Tropane alkaloids and toxicity of Convolvulus arvensis. Phytochemistry. 39(2):301-303.
Weaver, S.E. and W R Riley. 1982. The biology of Canadian weeds: 53. Convolvulus arvensis L. Can J Plant Sci 62:461-472. 


field bindweed, Convolvulus arvensis
field bindweed, Convolvulus arvensis
Kathy Keeler, A Wandering Botanist

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3 comments:

  1. Wow! Thanks for the wonderful article on bindweed. I am pleased to hear it is useful as a natural dye.

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  2. How can you get rid of them!! They are rapidly spreading in my horse pasture!

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  3. Control will be hard in a horse pasture. Pulling them out/ digging them out works but only slowly because it is so hard to get the whole root. The biological control mites reduce bindweed but don't eliminate it, but they can help. Bindweed doesn't grow well in shade. You might keep your pasture grasses tall to inhibit the bindweed. Of course, pull off flowers and especially seeds so that it doesn't spread that way. USDA says cattle, goats and sheep can eat it, but not horses. Here's the article http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_053357.pdf

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