late season invasives spraying

And so begins the Midwest’s Season of Gray & Brown. Most of the green in the landscape is gone, the pretty leaves have flown off the trees (yes, now even the oaks are reluctantly letting go).

Most, but not all.

Many of the invasive species in our area (which I’ve written about them previously) maintain their leaves longer into the fall. Perniciously, they also emerge extra early in the spring. As Michigan State U. extension says:

All of these honeysuckles are especially successful in dominating natural areas because of their ability to leaf out extremely early in the spring and remain green well into the fall. This means they have a leg up in these settings, essentially shading and out-competing native plants. These honeysuckles can eventually form dense thickets where little else can grow, including tree regeneration.

Land stewards can use this to our advantage, however. For a few weeks, it becomes very easy to spot populations of autumn olive and bush honeysuckle. “Wait… when did that population show up!?? Sigh…”

Not only are they green and visible, they are still photosynthesizing, unlike most of the other (dormant) plants. We can thus target them with herbicide from a backpack sprayer, and the plants move the chemical into their vascular system. On cold days this the plants are mostly shut down, but there are several warm days (~50 deg F or higher) where this is an effective strategy.

Even a single person with a backpack sprayer can make a lot of progress in a short time.

Blue dye is mixed with the herbicide to help the steward visualize where the chemical is applied.

One of the reasons this is effective is that it can be a great way to reduce collateral damage from overspray. Just “nuking” a wide swath around a single invasive plant is counter productive, because we are trying to get native species to occupy the same root space.

For example, in the photo below, the invasive Autumn Olive shrub is on the left, green and photosynthesizing. The location is a roadside ditch that has a substantial population of high quality native prairie wildflowers. On the right are the withered remnants of the leaves of the Prairie Dock. This perennial wildflower has abandoned this tissue for the year and survives overwinter as roots and buds, so it’s of little consequences if a few drops of herbicide land on the shriveled remains.

I was also hitting some invasive Poison Hemlock in the ditches, which is an increasing problem in the region. Then I came across the following:

There are some native Asters growing in and around the Hemlock. I could spray one without hitting the other. I skipped this one, knowing I could come back next spring and cut the flowering stalk of the Hemlock plant, interrupting it’s biennial lifecycle and giving the Aster the chance to spread.

These photos are all from Nov. 6. We’ve had a pretty hard freeze since then, so conditions have changed already. But there were still some goldenrods blooming, and insects foraging. The “growing season” is a simplification we use to make sense of our rhythms, but the reality is that many plants and creatures often live, move and have their being even in the cold. That’s a resilience we can aspire to!

One Reply to “late season invasives spraying”

  1. Mary

    Very helpful explanations of ecological work, Adam. These days when we begin to recognize “Integral Ecology”, this work helps us see and understand connectedness .


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