The warmer-than-normal weather during February had many people thinking about an early start to lawn and garden season. However, as temperatures have dropped and been below normal for much of March, it looks like we may have a couple more weeks before lawns really start growing. Lawn growth and crabgrass emergence are related to soil temperature, which is slower to change than the air temperature. While I have heard reports of soil temperatures topping out in the mid-50s for a day or two, it’s important to remember that in order to germinate crabgrass needs soil temperatures around 53-55⁰ F sustained for 5 days. These two things lead to a few questions, particularly pertinent this year when February felt like March and now March feels like late February.
Should I fertilize my lawn now?
While the legal window for applying fertilizer to lawns in Maryland began on March 1, that doesn’t necessarily mean you should fertilize your lawn just yet. Unless the grass is actively growing (which is dependent on warmer soil temperatures) it likely won’t take up and use the fertilizer—so you are better off waiting until the lawn is actively growing. Temperatures consistently around 60 and enough growth to warrant a second mowing are pretty good indicators of this. Keep in mind that if you fertilized your lawn in the fall you can probably wait until after the “flush of growth” in the spring (usually April/early May) and then schedule your spring fertilizer application for after that “flush” and leading into summer—usually around mid-late May. If you didn’t fertilize last fall it is tempting to try to “jump-start” the lawn in early spring with a fertilizer application, but hold off until the soil temperatures are consistently warmer and highs are around 58-60⁰ F on a regular basis.
Should I apply crabgrass pre-emergent now?
I would wait until soil temperatures are 53-55⁰ F sustained for 5 days. Keep in mind that your best defense against crabgrass is a dense turf that crowds out crabgrass seedlings. So, if you have good turf density and mow at 3” or higher, your overall crabgrass pressure should be lower anyway. The typical recommendation is to wait until the forsythia is “half green-half gold” (or even a little earlier), but with the warm February we had, that indicator may or may not be as accurate this year. You can check soil temperatures for your location at the following website: https://www.greencastonline.com/tools/soil-temperature.
Is there harm in applying crabgrass pre-emergent too early?
Probably not, unless it’s applied several weeks early and the product starts to break down before crabgrass even starts germinating. If you want to maximize the period of time your crabgrass application is effective, wait until when conditions are conducive to crabgrass germination and then apply it.
On another note, this is now the time of year when many winter weeds become more noticeable as they are likely producing flowers and setting seeds. While you can apply selective products to control these weeds, remember that these winter annuals like chickweed, purple deadnettle, speedwell, henbit, etc. are almost at the end of their lives and will die naturally once we have consistently warm temperatures. Another weed often noticed this time of year is the grassy weed called roughstalk bluegrass (Poa trivialis). Seeds of this grass are often a contaminant in turfgrass seed mixes (the cheaper the seed, the more likely you will have weed seeds) and this grass starts growing much earlier than tall fescue. As the temperatures warm, it is not as aggressive and noticeable. There are few selective control products that are labeled for roughstalk bluegrass and they tend to be restricted to professional sites and/or are expensive. If you only have a few patches in your lawn, digging these out (including the roots) and then re-seeding the spot with a soil-tall fescue mix is the best control approach for most homeowners.
By Geoffrey Rinehart, Lecturer, Turfgrass Management, Institute of Applied Agriculture, University of Maryland. Read more articles by Geoff.
Isn’t it beyond time to stop advising homeowners to routinely apply fertilizer and pesticides to their lawns? After all, homeowners are not maintaining golf courses or baseball diamonds.
1) Reduce or eliminate the amount of water and fertilizer used on the lawn. Apply fertilizer ONLY IF NEEDED BASED ON THE RESULTS OF A SOIL TEST. Use organic or natural (animal- or plant-based) slow-release fertilizers, after spring green and not during dormancy. Water in the morning to reduce evaporation and the potential for diseases.
2) Mowing: Cut the grass at the highest setting (3.5” is best, or no more than 1/3 the length of the leaf blade), to maximize root growth and shade the soil, preventing weed seed germination.
3) Allow grass clippings to remain on the turf to filter down and decompose as a natural fertilizer. Sweep any grass clippings that land on a paved surface and return them to the soil.
4) Reduce inputs: Mow less frequently. Use a battery-powered, electric or manual push mower if possible.
The prevailing suburban aesthetic of manicured turf monocrops comes at huge cost. The Chesapeake Bay Foundation’s 2022 annual report card for the Bay remains a dismal D+. Lawn fertilizer contributes to the phosphorus- and nitrogen-laden stormwater runoff entering the Bay, resulting in oxygen-depleted dead zones and loss of habitat for the iconic Blue Crab. In our increasingly hot and drought-prone summers, lawns require large amounts of water for irrigation and produce huge amounts of CO2 and noise pollution (from weed whackers, lawnmowers, and the like).
Let’s encourage people to reduce the amount of lawn in their yards — at 50 million acres nationally, we have enough — and replace it with turf grass substitutes and native plants that do a better job of sequestering carbon, supporting pollinators, beneficial insects and birds, and increasing biodiversity.
University of Maryland, I expect better. Lead with science and help change attitudes and practices that don’t serve the health of people or the environment. A little bit of crabgrass seems like a small price to pay. https://www.cbf.org/join-us/more-things-you-can-do/in-your-yard/lawn-care.html
Dorothy, Thanks for the comment on the post. I would be happy to respond offline if you would like to discuss. Feel free to give me a call at (301) 405-4692.
Thank you, Geoff. I appreciate that and will do so.