Shell’s Covert: Reducing Cool Season Sod-Forming Grasses Without Herbicides

On nearly every farm in our area, unless it is totally wooded, you will find cool season non-native sod-forming grasses like fescue and orchard grass. Ridding an area of these grasses can be one of the first and most important things a landowner can do to manage habitat for early-successional wildlife (if they are not needed for hay or stock grazing). I am encountering more and more landowners who wish to do this without herbicides. No soap box today. It can be done, but not without some patience and a lot of work. One more note—one never really rids an area of invasive species, one merely reduces them as much as possible and manages them through time.

For those not opposed to herbicides, I suggest you get a copy of Dr. Craig Harper’s booklet entitled “Managing Early-Successional Plant Communities for Wildlife in the Eastern U.S.” It can be found, along with other books by Dr. Harper, at https://fwf.tennessee.edu/craig-harper/. This booklet gets to the point about many scenarios commonly encountered on properties in the east and gives very good information on how to employ herbicides and other techniques with the most effectiveness.

Why now for this topic? Because fall, beyond a doubt, is the best time to start killing cool season grasses, whether with herbicides or not. I encounter many landowners who have recently purchased a farm and no longer plan to run cattle or cut hay, or they may be older landowners getting out of the business. Conditions range from pasture or hay fields in good condition to old fields having not been hayed or grazed for years, but still undergrown with cool season grasses. The goal is to reduce the cool season grasses and increase forbs. I’ll begin with the lightest footprint possible and go from there.

If you have old fields that have many beneficial plants growing in them—like goldenrods, partridge pea, pokeweed, black-eyed Susan, broom sedge, Indian grass, etc.—but still contain a good bit of fescue or orchard grass, one of the simplest things you can do to reduce these cool season grasses over time is to stop mowing or bush-hogging in the fall. Not only does fall mowing remove the beneficial plants at a time when they are most needed by pollinators, leaving no cover until spring, it also exposes the fescue and other cool season grasses to the sun when they are STARTING to grow best. In essence, you have removed their competition for sunlight and given them a shot in the arm… or leaf, in their case. If you delay mowing until early spring, you will begin to favor the more beneficial perennial plants in the stand. You will still accomplish your goal of keeping the trees from taking over.

Note also that prescribed fire can be applied in this manner to reduce cool season grasses to some extent. Understand that this is different than using fall fire to control woodies in conjunction with herbicides. Fall fire used without any follow-up herbicides will function similar to fall mowing in that it exposes the cool season grasses to sunlight and reduces their competition at a beneficial time for them. Fire will not kill cool season grasses unless multiple fires are used over a long period of time during the early summer growing season. Ideally, you would use fall fire followed by spot herbicide treatment to rid an old field of cool season grasses and control woody encroachment.

If you have a field that is vigorously growing cool season grasses better than everything else, more must be done. What follows also depends on site conditions, which includes slope and soil depth. These techniques won’t work well on shallow, rocky soils or on steep slopes. Some common sense has to be applied.

Natural succession on fescue field after heavy fall disking (vegetation the following summer).

It is possible to use a mold board plow, or in some cases a sub-soiler and ripper, to turn cool season sod over in the fall. If you do not have access to these implements, a heavy offset disk can also work to some degree. The idea is to expose the roots of the grasses to the cold weather all winter long, which will reduce them in the stand. To do this you have to get down deep enough in the soil to get those roots up and exposed to the air. Light shallow disking will accomplish very little. Prior to attempting this, the grass should be hayed, mowed, or burned off to reduce the heavy thatch and make pulling these implements through the soil easier. A fairly strong tractor will be required, 50 horsepower or greater in most cases. Timing should be just before frost in the fall, usually mid-to-late October in our state. If the ground is nearly level, it might be fine to leave the soil exposed with no cover crop. If you have concerns about soil erosion and want to plant a cover crop, the plowing can be followed up by disking and then sowing an annual cover crop like wheat, rye or oats (1.5 to 2 bushels per acre). If the land is sloped to some degree but not severely, the plowing and disking should be done perpendicular to the field’s slope, or on contours, to further reduce rain runoff. If the area is very steep, you should find another place to do this work (or consider using herbicides).

Heavy buckwheat cover crop.

Once the grasses have overwintered with exposed roots and a cover crop, I suggest repeating this process by disking and sowing a summer cover crop like buckwheat. A heavy cover of buckwheat (20 lbs. drilled, 30 to 35 lbs. broadcast) will help shade out the crabgrasses and continue to suppress the cool season grasses. Buckwheat also provides for honey bees and other pollinators. In fall, repeat by disking and planting a fall cover crop. Leave the field fallow the following summer and see what comes in on its own. At some point, you might want to plant a wildflower mix, but give it some time. The natural seedbank can be quite good. And no seed from a vendor will be as good as what’s in the soil naturally.

There are too many scenarios to cover in a blog post, but suffice it to say, by repeatedly using fall and summer cover crops, you may be able to deplete cool season sod forming grasses without herbicides. There are also some new techniques being investigated, such as propane burner systems that actually cruise slowly over sods to raise the grasses root temperature enough to kill them. This method has been effective on some smaller areas so far, and if it can be perfected, may hold promise as another non-herbicide method in the future. We’ll keep trying to think differently and keep you informed of advancements.

One Comment

Leave a Reply

Your email address will not be published. Required fields are marked *