Controlling Weeds in Tall Fescue Turf

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By Adam Smith

With winter around the corner, most of us plan to enjoy a temporary rest from all the work that goes into maintaining a great looking lawn. We’ve re-seeded, limed, and fertilized, and now all we have to do is wait for nature to do its work next spring. And work it does, bringing forth healthy green grass… and weeds. Weeds are the ubiquitous curse of every homeowner with a lawn, coming in all shapes and sizes and growing where we do not want them. Some of us resign to the idea that a weedy lawn is better than no lawn while others prepare to go to battle. The war on weeds can be won, but know that it must be continuously fought.

There is no better weed control than healthy thick turf. By leaving no space for weeds to grow, established healthy turf will naturally be at an advantage against germinating seedlings, and proper overseeding, fertilization, and mowing practices can help you achieve that goal. For a cool-season turfgrass like tall fescue, this means mowing your lawn at 3.5-4 inches and mowing frequently enough to only remove the top ⅓ of the leaf blade at a time. It is also important to overseed your lawn each fall. Tall fescue should be seeded at 6 lbs per 1000 ft2 in the month of September. This allows adequate time for your new turfgrass seedlings to germinate and establish before cold weather increases the chance of injury. It’s important to maintain moist soil via regular irrigation to prevent newly germinating seedlings from drying out; expect to see germination occurring 1-3 weeks after overseeding.

Equally important for your tall fescue lawn is fall fertilization. Those new seedlings need proper fertilization in order to ensure a strong turfgrass stand. Previous recommendations suggested three fertilizations dates: Valentine’s Day, Labor Day, and Thanksgiving, as the ideal times to apply your fertilizer. However, new recommendations state that those dates should be considered rough estimates and that it’s more important to apply fertilizer before soil temperatures drop below 50°F. Applying fertilizer as a single application or in a split application depends on the homeowner preference, but it’s important to note that tall fescue should receive a total of 1.5-2 lbs N per 1000 ft2 each fall.

Oftentimes healthy grass is simply not enough and additional control is needed. Herbicides are powerful tools, that when used appropriately, can control the vast majority of the weeds in your lawn. Herbicides are categorized based on what weeds they control and how they control them. There are broadleaf herbicides that only control broadleaf weeds such as white clover, dandelion, and chickweed, and there are grass herbicides that only control grass weeds such as large crabgrass and goosegrass. Furthermore, those herbicides are categorized by how they control weeds. Preemergent herbicides control weeds before they emerge from the ground, and post-emergent herbicides control weeds already established in your lawn. For most of us, our primary concerns are controlling broadleaf weeds that have already established and in preventing grass weeds like large crabgrass from emerging.

To use herbicides for additional weed control, apply a preemergent crabgrass herbicide in late winter/ early spring to prevent crabgrass seedlings from emerging. The general rule of thumb is that a preemergent crabgrass herbicide should be applied when Forsythia is in full bloom (February). The applied herbicide should be irrigated into the soil or applied before a forecasted rain. To control existing broadleaf weeds, a 2,3, or 4-way broadleaf herbicide is the best option for controlling those weeds. These herbicides have multiple chemistries that allow for a broad spectrum of weed control and are generally safe on cool-season turf like tall fescue. For any herbicide, be sure to read the label. The label always states what turfgrass species are safe to use the product on, what weed species the product can control, and how to use the product appropriately and safely.

N.C. Cooperative Extension of Catawba County works to serve the community by providing research-based consultation and educational programming. On December 11, 2018, from 10 a.m.–noon, we’re excited to offer two courses for homeowners and professionals alike. From 10–11 a.m., there will be a Sustainable Landscape Ideas course. The course will be taught by Anelle Ammons and will cover topics like permaculture, increasing the sustainability of your yard, and home food production. From 11 a.m.–noon, there will be a Turf Weed Management course. The course will be taught by Adam Smith and will cover topics such as weed identification and biology and cultural and chemical weed control options. For professionals that attend both courses, one can earn two pesticide credits (D, L, N, X) and/or two landscape contractor credits (L). The courses will be held at the N.C Cooperative Extension of Catawba County office at 1175 S Brady Ave in Newton. Please call our office if you have any questions about these sessions – 828-465-8240.