While there have been many plantings that do not receive first-year weed control and turn out successful, there are dangers with doing nothing. Weed pressure can kill native plant seedlings, but even if this doesn’t happen, the weed pressure usually slows the establishment of the planting. For these reasons, weed control is highly recommended in the first year after planting when these quick-to-establish weeds are abundant. Weed control opens up the canopy and reduces the competition, which allows the developing native plant seedlings to get needed sunlight, water, and nutrients.
What weed pressure should I expect the first year?
The first growing season after planting, it’s normal to see an abundance of annual weeds growing in the area. Annual plants only live one year, and do NOT come back from the root (like a corn plant). Because these annual plants are opportunists, the seeds have been waiting in the soil for a time such as this—bare soil and no perennial plant competition.
Commonly encountered annual weeds include ragweed, foxtail, crabgrass, pigweed, lambsquarter, and so many more. For the most part, these annual weeds diminish following the first few years of the planting because as the native perennial plants develop, their competition makes a much less hospitable environment for the annual weeds. Watch the video First Year Native Planting: What Should it Look Like? to learn more.
However, not all weed pressure is from annual plants. Quick-to-establish perennial plants, which come back from the root system year after year, can also be a problem. White clover (also called Dutch white or ladino clover) is often a problem in old pastures that are being converted. With its short height, white clover is usually outcompeted in the long term, but in the first year or two it can be incredibly competitive.
In some plantings, annual weeds are not much of a problem. There may not be many weed seeds in the seedbank (e.g. in a savanna/silvopasture restoration where trees have been thinned). Herbicides used during the establishment process may help control the annual weed competition. Panoramic (also called Plateau, active ingredient imazapic) and Atrazine are used when establishing certain native plants and both serve as pre-emergent herbicides, discouraging the germination of the annual weed seeds found in the soil.
What problems do the annual weeds cause?
Annual weeds have only one year to live so their mantra is, “Forget the roots and grow a stem and leaves quickly.” On the other hand, most native plants are perennials, meaning they establish a strong root system to come back from year after year. Because most of the native plants focus on building this root system in the first year, the above ground part of the plant often doesn’t get very big. So, the problem comes in when the native plants seedlings struggle to find the sun’s sustaining strength under a dense shadow of annual weed pressure. The annual weeds also compete for water and nutrients.
The problem with annual weeds is not permanent—rather it is just in the first few years. As time passes, the native plants mature, grow taller, and occupy a bigger footprint. This usually discourages the annual weeds, and their presence markedly decreases.
What can I do about the first year weed pressure?
There are generally three choices for controlling weeds the first year: mowing, herbicides, and livestock, but not all of these tools can be used in all plantings. Viable options for first-year weed control depend on what type of natives plants have been planted. In plantings where only grasses have been planted, all of the options may be considered. However, in plantings with a diversity of native grasses and native forbs (wildflowers), mowing and livestock are the only viable options since no herbicide kills only weeds and leaves the native plants. Below is a brief description of these methods:
Sometimes described as giving the planting a haircut, the goal of mowing is to cut the top off the weeds thereby reducing competition for the shorter native plants. Mowing works particularly well with weeds that have most of their green leaves above the mowing height. Watch the video Sickle Mower vs Brush Hog for Weed Control in First Year Plantings for more mowing information.
In a controlled situation, livestock may serve much the same purpose as mowing. The aim is to remove some of the greenery from the weeds without allowing the livestock to graze off the native plant seedlings.
Some herbicides kill only a certain group of plants while not affecting the plants outside of that group. In a first-year grass planting, you can use selective herbicides to remove broadleaf (non-grass) plants. When using herbicides, always read and follow label directions to ensure not only the health of the planting but also the people and environment.
What can I do about perennial, invasive weeds?
During the establishment process, all of the perennial weeds (those that come back from the root system year after year) should have been killed. Sometimes there may be seeds of these weeds remaining in the soil, but there should be no living perennial weed plants when the native seed is planted. Because the perennial weeds that germinate from seeds in the soil first develop a healthy root system, they usually do not have considerable top growth the first year or two.
Whenever perennial weeds do show up, whether that is the year of planting or later, reference Maintenance: Controlling Invasive Plant Species.