Restoring Bottomland Prairie: Controlling Crown Vetch, Promoting Canada Milkvetch

Agricultural "experts" imported Crown Vetch from the Mediterranean, other "experts" recommended it for erosion control, and it's been an invasive in North American landscapes ever since.

Once established, Crown Vetch

forms a tangled mat.   

One of those know-it-alls told Bird Runner's previous owner to plant it along McDowell Creek--so we've had to battle it ever since 1999, when we created a 4.7-acre native-plant riparian buffer between our Creek Field and the creek.

Therefore, for 16 years we've been locked in struggle with Crown Vetch (along with other exotic invasives, such as Poison Hemlock & Garlic Mustard).  

Golden Alexanders claim territory on the riparian buffer 

  from which Crown Vetch has been removed.   

That's  a Gorgone Checkerspot nectaring on the blossom.  

But look what's lurking in the background!  

The Crown Vetch has retreated into a thicket, just waiting to

expand again.   

Native plants are claiming more and more of the  riparian buffer, so every year there's less & less uprooting or spot-spraying of exotic invasives that needs to be done.

But the invasives are still there, and they're still ambitious!

Since we re-seeded the entire Creek Field back to native in 2013, we've been determined to keep the invasives on the riparian buffer from ever getting into the Creek Field!

In that effort, as always, our greatest allies have been the native plants themselves.

In particular, we've had help from a native vetch, Canada Milkvetch (Astragalus canadensis).  

Here are the lovely white blossoms of Canada Milkvetch, in
front of two blooming yellow Plains Coreopsis.
 Canada Milkvetch does not form a mat as does Crown Vetch.
With Canada Milkvetch, you can always distinguish one
individual plant from another.  Also, the leaves have a blue-
green cast (but not always) unlike the bright-green of Crown
Vetch.

Who can get rid of a bad guy with roots?   A good guy with roots!

Canada Milkvetch germinated the first year, multiplied the second year, and this year has even spread from the Creek Field into the riparian buffer!

But now we human helpers of native plants have a new problem:  how to tell the sprouts of Crown Vetch from those of Canada Milkvetch. We don't want to destroy the latter when we're after the former!

The seedpods of Canada Milkvetch
are unmistakeable.

In maturity, the species are easy to tell apart.

 But when they first come up, either species can be erect or sprawling, and both have similarly shaped leaves with odd-numbered leaflets.

Canada Milkvetch Leaf

Crown Vetch Leaves
(Plant Bug, Lygus sp., upper left)

To the rescue:  Mike Haddock's marvelous book, Kansas Wildflowers & Weeds.   From his book I learned that Canada Milkvetch, unlike Crown Vetch, has tiny hairs pressed into the surface of the leaflets.

Under magnification, the tiny hairs are visible on the leaflets of Canada Milkvetch.

At first I couldn't see this feature with the naked eye--but now that I have photographed the leaves of both species, and magnified the photos, I know what to look for.

Now that I have seen them in photos,  I can see those hairs in the field, even with eyes unaided.

Thank you, Mike!

Your book is helping the native plants re-take the field.