Wednesday, June 29, 2011

New Crown Vetch Infestation

A little foray through the field turned bad when I found a Crown Vetch blossom in my path. Crown Vetch was once planted on steep banks and other hard to maintain areas for erosion control and wildlife habitat. Having had some little success in that role, it went out on its own and made a name for itself as a non-native invasive species. It’s not a plant I want growing at Blue Jay Barrens.

It starts innocently enough with a few shoots coming up through the existing vegetation. Its sprawling growth habit will soon cover and then smother the neighboring plants. The takeover is not rapid, so it may be several years before it becomes obvious that the plant is a problem. By that time it’s so well established that its removal becomes a very complicated process.

The most troubling facet of this new infestation is its location. The new plants are growing right in the middle of the field. There are other patches of Crown Vetch growing at Blue Jay Barrens, but they are all near the road where they had been seeded in an attempt to stabilize steep road banks. The embarrassing thing about that is the fact that the agency I work for funded the seeding through a cooperative agreement with the County. It all happened over 30 years ago and it’s not something we would do today, but the locations of Crown Vetch infestations moving into my fields match exactly those of the seeded road banks. I guess that’s the cost of an education.

Crown Vetch is a legume with a flower cluster resembling that of White Clover. Its ability to utilize atmospheric nitrogen gives it an advantage on poor soils. The plants that it kills fall to the ground and decompose to release nutrients that are used by the vetch. It flourishes under these conditions. A solid mat of vetch plants eventually develops and little else will be found growing there.

There were few enough plants in this spot that I could probably have pulled them all and eliminated the stand. I would have done that, but I was afraid the plants had produced seed in earlier years. Crown Vetch is a prolific seed producer and seeds in the ground will germinate and continue the infestation. I chose to spray the patch with glyphosate. This will kill all plants growing on the site and will produce a bare spot that will make it easy to spot any emerging Crown Vetch seedlings. The dead spot will be small enough that neighboring plants will quickly fill it in. While that’s happening I can keep an eye on things and make sure that it is clean of vetch.

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