May is a Good Time for Invasive Shrub Control in Prairies and Savannas

At Black Earth Rettenmund Prairie we have three burn units, and burn each on a rotation of two out of each three years. Thus, each year we have one unburned unit and two burned ones. Each year a different unit is left unburned.

The unburned unit is the one in which we do invasive shrub control.

Invasive shrub control focuses on the unit which is in its “off” burn year. Invasive brush in that unit is easy to find, because the above-ground buds are alive and leaf out. They are thus easy to find during a stroll through the unit and are easy to kill because they are not very large.

How to kill the invasive shrubs?

• If it is a single isolated plant: cut each stem of that plant with a hand clippers and treat the cut stem with herbicide (Garlon 4 at 20% concentration in bark oil)
• Or: don’t cut but treat the stem near the base (basal bark) with Garlon
• If it is a large clone such as one often finds with aspen, hazel, buckthorn, or sumac: cut the whole clone with a power brushcutter and treat each cut stem with Garlon
• For isolated stems of a straight-growing plant like aspen: swipe up from the base of each stem with a sponge stick loaded with Garlon in oil

This “one-out-of-three” approach makes a lot of sense, because you only have to do invasive shrubs in one-third of the prairie.

Hopefully, there are no invasive shrubs in the two units that were burned this spring. However, any straggling invasive shrubs that might be present would have been top-killed so they do not leaf out.

However, if there are still invasive shrubs in the units that have been burned, they can be dealt with later in the summer when they have resprouted and are tall enough to find. Or even better, wait until late fall, after all the native vegetation has senesced, and the invasive shrubs can be found more easily. Then use one of the treatment methods listed above.

Note that invasive brush can also be worked on all winter, even when there are no leaves. Again, any of the methods listed above can be used.

An important point: you can’t eradicate invasive brush in a single year. It is essential to return year after year, since there will be resprouts or root suckers or new seedlings which will turn into shrubs. Keep at it.

Black Earth Rettenmund Prairie looking south across the Saddle Unit from the North Unit. The brown patch in the background is the unburned South Unit, where brush control will be carried out.