Of Invasive Weeds: Crown Vetch and Yellow Rattle


Crown vetch


Yellow rattle

Two obnoxious weeds are trying to take over our farm. Crown vetch and yellow rattle were both accidentally introduced to our land several years ago.

Crown vetch (Securigera varia) is a perennial legume native to Africa, Asia and Europe that was brought to the US in the 1950s for erosion control.  Since then it has shouldered its way into most of the nation, pushing out native flora and making a general pest of itself.

The weed is toxic to horses and most know better than to eat it.  There are no natural predators of crown vetch here.  It can grow unmolested in prolific abundance.  The only ways to eliminate it are hand pulling of the tough underground rhizomes, assiduous mowing several times per year, or poisoning with weed killer.

The State of Maine Department of Transportation introduced crown vetch to our land when they reconstructed the road and seeded the sides.  This occurred twenty-six years ago.  Most of those years, the vetch behaved itself and stayed by the road.  Then a few tractor breakdowns and late mowings allowed the weed to spread, sending rhizomes and seeds into our orchard.  Once seeds are dropped by this weed, they are viable for years in the environment.  Since we have an organic farm, I won’t use chemical weed killer.  The vetch invaded about a half-acre of orchard, too much to hand-pull.

Luckily, this year we have a brand new weapon, a 2013 New Holland Workmaster 55 four-wheel drive tractor that starts and runs when you need it. b1Unlike our last tractor.  The lethal Woods Rotary Mowing Machine, with a six-foot cutting swath, attaches neatly to the three-point hitch on the back of the tractor. At 2540 rpm, nothing argues with the spinning blades of the mower.b6

I mowed the crown vetch in the orchard, getting accustomed to my new rig, and discovering that any serious orchard mowing will require removal of the bucket assembly.  Luckily, the vetch grows mostly in open areas where I don’t have to do fancy maneuvering between the apple trees.

This nasty weed must be cut, at the least, in June and August, and also probably in July and September, killing it before it can bloom.  The invasive plant experts say that after several years of dedicated mowing, crown vetch can be controlled.  Fingers crossed.  If the vetch continues to march down the hill and takes root in my pasture, disaster.  It kills all other plants and forms a mono-culture.  Horses won’t eat it, so my animals would not be able to graze their pasture if crown vetch took over.

Yellow rattle (Rhinanthus minor) is a native annual plant, a relative of snapdragon, that prefers open, sunny locations such as my hayfield.  There was no rattle in my field for most of my life.  Then, a few years ago, I found a clump growing near the entrance to the field.  Seeds probably fell from the haying equipment of the farmer who cuts our field.  Unfortunately, I didn’t grasp the danger of those few little yellow-flowered weeds and let them stay.

Yellow rattle forms seeds in each of the large, round, flatish pods below the flower.  When the seeds mature, they rattle in their pods, hence the name.  b5Cute and kind of fun to shake, until the full extent of the catastrophe becomes obvious.  As it did a few days ago. I took a tour of my growing hayfield and discovered yellow rattle had taken over at least three-quarters of the area.  The weed discourages grass growth by sending parasitic roots into grass roots and stealing nutrients.  Where the hay should be tall and ready to bloom, rattle bloomed instead, in yellow excess.

The first crop of hay is ruined.  Since yellow rattle is an annual, stopping it from seeding should kill it.  The seed can remain viable for at least three years.  The weed was able to spread because my field isn’t hayed until July or later, after the rattle blooms. Haying only spread the seeds far over the area.

I spent most of this week destroying my first crop of hay.  Making repeated passes with the mowing machine nearly dragging on the ground to cut every last one of the dirty little rattles.  I am hoping for a strong second crop of hay so I don’t have to buy all my horse fodder this year.  Usually we make the hay the horses need from that field.  Since we have no haying equipment, we depend on another farmer’s schedule for hay cutting.  I can only rotary mow, which destroys the hay.  The destruction of the first crop will likely need to continue for the next two years to eliminate the rattle.

As I mowed the hayfield, I discovered a pair of bobolinks nesting.  Bobolinks prefer grassland and build their nests low, on the ground.  The poor birds were having a fit as the tractor neared their area.  I was having a fit, as well, because I needed to mow all the yellow rattle, yet I certainly didn’t want to destroy the birds’ nest.  Bobolinks are beautiful, with a lovely song, and their numbers are declining.  I stopped mowing where they were and hoped I hadn’t already gotten the nest.  As luck would have it, the location the birds chose was one of the few spots with no rattle.  I was able to leave two large plots of standing grasses for bobolink habitat.  The birds are still there two days after the mowing, so I must have avoided the nest.  I shudder to think of all the bird nests that are destroyed this time of year as farmers hay their fields.

So now we shall see if my efforts of the past week are successful.  I have learned a hard lesson, especially about yellow rattle.  When something new appears in the landscape, learn about it.  Early knowledge can prevent much later misery.



2 thoughts on “Of Invasive Weeds: Crown Vetch and Yellow Rattle

  1. Your father decided to plant the crown vetch. I can remember his planting of it. It seemed a lovely ground cover. I am not familiar with yellow rattle. You sure have your work cut out getting rid of these weeds. I am so glad you have your tractor weapon to use on them. So glad the bobolinks are ok.

    • Yes, I think I recall him planting some crown vetch as well. The stuff I’m battling in the orchard was put there by the State. It was planted when they re-did the road, after we moved to the farm. They also sprayed the seed on the lower side of the lovely driveway mountain the State created for us. I’m able to keep that area of vetch in control.

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