Join our Sorghum Event September 11 & 12, 2026. You can RSVP here.
Mowing can be a highly effective first-year annual weed control strategy when establishing a native planting. It is an especially good choice when the planting contains both grasses and wildflowers. When used correctly, mowing reduces weed competition while protecting young native seedlings. This guide explains why, when, and how to mow during the establishment year.
During the first growing season, reducing weed pressure is critical. Perennial native grasses and forbs (wildflowers) typically grow more slowly than fast-growing annual weeds. Some weeds can double their height in a single week.
The goal of mowing is not to eliminate weeds. Instead, mowing gives weeds a “haircut,” temporarily reducing their height and vigor so native seedlings receive more light, space, and resources.
Timing is the most important factor in successful mowing.
Start observing plant growth in early June for central latitudes (if the planting is in the south, start monitoring earlier and for those further north, you may be able to start later). Many plantings will not require mowing yet, but it is a good time to start keeping an eye on the planting.
We recommend mowing when weeds reach 70-80% canopy coverage. When the weeds have significant canopy coverage like this, they are competitive with and significantly shade the native seedlings. Waiting for a fuller canopy coverage of the weeds helps to minimize the number of times that the field is mowed during the first growing season. This reduces the chances of the equipment tires having a negative impact by harming some of the native seedlings. The fewer passes across the field the better.
To evaluate canopy coverage, stand in the field and look down. A canopy coverage of 70-80% will mean that there is significantly more ground covered from view by vegetation than is visible. A good test for this is the “Boot Test”. To do this test, simply look down at your boots when standing in the field. If it is difficult to see the toes of your boots due to the vegetation, it is probably time to mow.
During drought, existing vegetation can provide beneficial shade that reduces seedling stress. If plants (weeds or native seedlings) are showing significant drought stress, it may be beneficial to wait to mow until the plants receive adequate rainfall and appear less stressed.
It is generally not recommended to mow during the 45 days before your average first date of frost. By late summer, many seedlings are allocating energy toward root development and winter preparation and disturbing them in the mowing process can affect the ability to store root reserves for winter. This principle is most applicable to Native Warm Season Grasses and forbs (wildflowers) that go dormant (are brown) during the winter. Native Cool Season Grasses and forbs (wildflowers) that are green during the winter may still benefit from mowing right before frost because these native species will continue to grow for a period of time after the frost.
Correct mowing height protects desired seedlings. Basically, the principle is to remove as much leaf area of the weed as possible but minimize the removal of the natives’ leaf area.
In most cases, it is best to set the height of the mowing equipment above the height of the seedlings so that the seedlings are not being cut off. It can be difficult to find the native seedlings because they are so small, but it is worth putting some effort into finding them, so you know how tall they are.
How can I find these tiny seedlings?
Seedling identification can be difficult. First, check your seed tag or invoice to know what you planted, then check out these resources for identification of some native plants which are often abundant in plantings or easy to identify. Partridge Pea is an annual legume that usually germinates early and is easily identified. Wild Ryes are a cool-season, perennial grass, and they germinate earlier than the Native Warm Season Grasses. Big Bluestem and Indiangrass are warm season grasses that are commonly included in plantings, often as a large percent of the stand, and consequently, being able to identify them can be quite useful.
The weed should be cut off as low as possible without damaging the native seedlings.
At times, the weeds should be mowed at a height that will also mow off part of the growth of the native seedlings. If you find this to be the case, keep these thoughts in mind:
Annual & biennial native seedlings
These quick-growing native species, such as Partridge Pea, Plains Coreopsis, and Common Black-Eyed Susan, are aiming to grow to maximum height and produce seed the first or second year before they die. As such, they are generally taller in a first-year planting than the perennial native seedlings, which are focused on developing a deep root system. It is common that the annual and biennial natives are as tall as the annual weeds that you would like to mow off.
How can you avoid mowing off these annual and biennial natives while still mowing off the weeds? You can’t.
In most cases, it is advisable to focus on the native perennials and mow at a height so that the perennials are not cut off, which means that the native annual and biennials will be sacrificed. Keep in mind that if they do get mowed off, the native annuals and biennials may grow another set of flowers. Also, additional seeds of the native annuals and biennials may be added the following winter (dormant season) to make sure these species are in the seedbank.
Minimize leaf area removal of the natives
Sometimes even the perennial natives may be tall enough and the weeds short enough that the cutting height decision is difficult. Just keep in mind that the principle is to remove as much leaf area of the weed as possible but minimize the removal of the natives’ leaf area. Ask yourself, “How do I hurt the weed without hurting the natives?”
Mowing is a responsive management tool, not a fixed schedule.
Weed structure determines mowing effectiveness. To some weeds, mowing is a significant setback while others are not impacted.
Tall, upright weeds with leaves that are positioned at the top of the plant are ideal candidates for mowing. Like an umbrella, the stem of the weed is like the stick/handle and the leaves at the top of the plant are the umbrella’s canopy. Mowing is an effective tool when the “umbrella’s canopy” can be cut off. In other words, a weed is a good candidate for mowing when the mowing will remove a large portion of its leaf area causing it a significant setback.
Examples:
Low-growing weeds with leaves close to the soil surface are poor mowing targets. Like an upside-down umbrella, the canopy cannot be removed without also cutting off the native seedlings.
Examples:
Some weeds are intermediate in shape and mowing helps to some extent to open the canopy back up for a short period of time. Mowing these weeds makes the most sense if they are growing in a particularly dense stand or are mixed with weeds that do mow well.
Examples:
Equipment choice affects seedling safety. Ideally avoid equipment that heavily shreds plant material or leaves thick windrows. We want a clean cut and no thick mats of dead plant material.
Avoid these frequent issues:
Mow only if weeds are becoming competitive. Use canopy coverage and weed height as decision triggers.
The mower height should be above the native seedlings.
Most plantings require one to two mowing events during the first season. Weed canopy coverage should be the trigger to determine how many mowing events.
Mowing is one tool among several. For diverse native plantings that include both grasses and wildflowers (forbs), mowing is usually the best tool. However, for plantings that only have native grasses or only native wildflowers, herbicides can be an effective tool.
Late mowing can disrupt seedling root development and winter preparation of Native Warm Season Grasses and some forbs (wildflowers).
Proper first-year mowing supports long-term success. Thoughtful timing, correct height, and appropriate equipment help native species gain a foothold while keeping weed competition in check.
