Adding Diversity to Existing Warm Season Grasses
Following an establishment plan
To maximize your investment in seed, follow the establishment plan to get the best chance of success. These timelines are guidelines. Weather and individual situations can change the process and the dates mentioned are only recommendations.
During establishment and for the life of a native planting, always consider the movement of seed with vehicles and equipment. We recommend you blow down or wash off equipment and vehicles before entering the field, especially if the equipment/vehicle was recently used in a field ripe with seed of a species you do not want in your native planting (e.g. fescue, sericea, Johnsongrass).
Choose the best timeline
If you’re not sure this is the right establishment plan for your situation, use our Planting Timeline Selector or read the Establishment Plans Overview.
Adding other grasses & wildflowers to your planting
This is a method to use when you want to add diversity to an existing native warm season grass (NWSG) stand. It is especially applicable if you want to add a good component of native cool season grass and native forbs. If the pasture contains Bermudagrass, Johnson Grass, Sericea Lespedeza, Caucasian Bluestem, Crown Vetch or other problematic species, the guidelines may need to be adjusted. However, cool season plants such as tall fescue can be dealt with as part of this plan.
Note: Overseeding when the existing plants are mature is never as good as planting all the species at one time, and more seed may need to be planted to get the same effect as the new seedlings will be competing with big, deep rooted, established native warm season grasses. This means the seedlings may have a higher mortality rate and they may be slower to establish.
- Stress existing planting two times
summer / fall before frost, year 1
Because the existing NWSG plants provide so much competition, you need to weaken them somewhat and create plenty of exposure for the herbicide (used later in the process) to reach undesirable cool season grasses.
However, if the NWSG plants are in their first growing season, skip this step because the existing grasses are not yet well developed and will not compete against the new planting the way older, established grasses would
Mowing, haying, prescribed burning and grazing are all tools that can be used to weaken the existing NWSG. If it is feasible, perform any combination of two of these actions. The first action can be variably timed, but should be before the late summer/early fall rains are anticipated to begin, and at least 30-45 days before the next action.
The second action should be timed 30-45 days before frost, which is a time when the NWSG transport root reserves down below ground. If it is not practical to do two actions, do one action and time it 30-45 days before frost. Most often when two actions are taken, they are usually the same action (e.g. the person who hays it the first time often hays it the second time) simply because that is a tool that they are comfortable with and have the equipment/livestock for.
Here are a few notes on mowing, haying, prescribed burning and grazing to weaken plants. Be aware, this is not how these tools are not prescribed for a healthy stand of plants. These instructions are only to be applied when you need to weaken and stress the existing plants.
Haying
The best match of quality and tonnage is usually to take the first cutting from NWSG around mid-June to mid-July (depending on the species of NWSG). When hay production is a goal, NWSG are not typically hayed twice during a single growing season because it weakens them. Thus, a second cutting around 45 days before frost can help to weaken these big NWSG to allow for a more successful overseeding of diverse grasses and forbs. When haying for the purpose of weakening the NWSG, it may also be a good idea to cut lower than is advisable for maximum plant health — probably below six inches.
Mowing
The same basic approach may be taken in mowing as haying for the purpose of stressing plants. Mow at a height of six inches or less. Mow twice, the first being mid-June or mid-July up to about 90 days before frost. The last should be about 45 days before frost. Mowing may also pair well with a prescribed fire if there are enough brown grass leaves to carry the fire. Because mowing returns the cut off plant material to the soil, you’ll need to be more intentional to make sure seed-to-soil contact is achieved during the planting step.
Prescribed fire
There must be enough dead, brown plant material to carry a fire. If when coming out of winter there is a good component of material to carry a fire, a prescribed fire could be used with success between mid-June and 75-90 days before the first frost. However, with the high humidity of summer it can be difficult to get a successful burn during this time frame. If it is achieved, a different tool (haying, mowing, or grazing) can be used in the 30-45 days before frost timeframe.
On the other hand, prescribed fire can be used as a last step about 45 days before frost and the first step can be mowing (the other two actions, haying and grazing, are not likely to leave enough material to carry a fire). A single prescribed burn about 45 days before frost, not combined with another weakening action, should also provide some stress to the existing NWSG.
Grazing
This action can be done throughout the growing season almost in the same manner as would normally be done. A few modifications to the grazing prescription can have the impact of weakening the NWSG that grazing would normally stimulate. Under ideal management, NWSG are not grazed too short (maybe 8-18 inches, depending on the grazing management system) and are allowed at least 45 days of recovery between grazings. However, repeated grazing that is below an 8-inch residual and that is more frequent than 45 days can weaken the established NWSG.
- Spray undesirable cool season grasses
November – December year 1 or February – early March year 2
When the NWSG plants are dormant, glyphosate can be sprayed over top of the NWSG with no ill effects on the NWSG, but any green and growing plants, such as tall fescue, can be killed with this application of herbicide. It is very important to make sure the glyphosate application is timed after a hard freeze when the NWSG are fully dormant or before they begin to green up in the spring! The dates will vary depending on your location.
- Plant native seeds
January – February 15, year 2
January is a great target, but you need to complete planting the new seed before February 15. Many species of the native forbs and native cool season grasses need to be stratified (go through a cold, moist period) before they will germinate, which is why planting in winter is the best. It is imperative to get seed-to soil contact so either shallowly drill the seed or do a prescribed burn before seeding or drag but do not use disking.
- Graze, mow, or hay
End of May – June, year 2
Spring has sprung and it is time for the NWSG to grow again. Ideally, the NWSG canopy would be reduced during the first year so that the developing seedlings can get plenty of sunlight. Grazing and haying the NWSG are excellent tools, but make sure the small seedlings of diverse natives are not grazed or cut off.
Haying
Don’t cut below 6-8 inches and minimize the trips across the field with machinery because tire traffic is hard on seedlings.
Mowing
Don’t cut below 6-8 inches and minimize the trips across the field with machinery because tire traffic is hard on seedlings. Also make sure that the cut-off plant material does not smother native seedlings.
Grazing
Make sure the livestock are not eating off the small seedlings. Graze in a rotational grazing system with a short grazing window because this gives a greater degree of control and easier observations of what the livestock are eating. Also, in the subsequent dormant season, don’t graze it more than once in this first year after planting since the cool season plant material is still in the establishment phase.
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