Tom's Blog

Tuesday, April 26, 2011

Post-burn spraying of new shoots of invasive plants

Now that burn season is over, it is time to turn to early control of invasive plants. One of the main advantages of burning a natural area is that it creates a barren landscape where new shoots can be readily seen. Although most of the "bad guys" (sweet clover, wild parsnip, etc.) are not up enough yet to find, some species are already visible. Among these is the strongly clonal Arnoglossum atriplicifolium (pale Indian Plantain, which we are calling PIP), which is already widespread at Pleasant Valley Conservancy. Although we don't have garlic mustard, we do have this annoying invader.

Those who have been following this blog will remember that last summer I discovered that PIP forms extensive rhizome systems and forms root suckers throughout. In our sort of savannas, it is highly invasive. (The fact that this is a clonal species had been published over 25 years ago in an obscure botanical journal, but was not generally known in our area.) Last summer's clones were so large and dense that no other species was able to become established. We spent a lot of time getting rid of this species, but knew that we were not eliminating the underground rhizome system.

We therefore determined that this spring, in an effort to eradicate the rhizome system, we would start spraying new shoots as soon they were visible.

As it turned out, PIP was one of the first species to appear in areas where it was clonal, even before other cool-season forbs (such as shooting star, columbine, golden Alexanders, etc.) Since it grows in large colonies and has characteristic leaves, it has been easy to spot. The photo to the left shows a typical scene. Each shoot has arisen from a root sucker on one of the underground rhizomes. In a circular area about 20 feet in diameter, I estimated that there were around 1000 shoots! Because of the black background remaining from the burn, these shoots stand out well. Even the tiny ones (a few visible in this photo) could be spotted.

Fortunately, last fall we had made careful notes of where this plant was present, and were able to start spraying about a week ago. Amanda spent a couple of extra days on some of the densest stands, Kathie and I both took our turns, and the complete crew will endeavor to finish the job within the next week.

We elected to use a foliar concentration of glyphosate (2%), since this herbicide has no residual activity in soil and will not affect later-growing species.

However, we are planning to return to all sprayed sites in about 2 weeks and respray any newly appearing plants or those missed on the first pass. Any that we don't get in the second pass will be dealt sometime in early summer using the Garlon leaf spritz technique . (This species forms large basal leaves, making the leaf spritz technique especially effective.)

After we had finished our spraying for the day, Kathie dug up a few plants from one of the sandier savannas. In sand, the roots are easy to clean of soil, making it possible to see what these young suckers look like. As the photo shows, these tiny plants have massive root and rhizome systems. Also, at the base of each stem is a cluster of dormant buds (not visible in the photo). Obviously, you can't get rid of a plant like this by pulling it up, since you will never get all the rhizomes. Herbicide is the only way.


Blogger Mandie said...

How well did this method of control work?

August 8, 2011 at 11:46 AM  
Blogger Mandie said...

How well did this method of control work?

August 8, 2011 at 11:46 AM  
Blogger Tom's Blog said...

This method worked very well. The invasive clone was virtually completely eliminated. We returned in June to spray the few stragglers that appeared after the spraying had been done.

August 8, 2011 at 12:41 PM  

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