Early Spring Lawn Tips for Fertilizer and Pre-emergent Timing

Speedwell is a winter annual weed. It will end its life cycle and die naturally once we have consistently warm temperatures. Photo: G. Rinehart

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.

grassy lawn weed called roughstalk bluegrass
Roughstalk bluegrass (Poa trivialis) is a cool-season weed that shows up in early spring. If you only have a few patches, you can dig them out by hand (including the roots) and overseed to fill in the bare spots. Photo: G. Rinehart

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.

Spring Lawn Care Tips & Bay-Friendly Lawn Workshop

Spring appears to be on schedule for most of Maryland as temperatures are slowly creeping up into the 50’s and 60’s for highs. One of the temptations for homeowners is to fertilize the lawn “to get the grass going” in the spring. Keep in mind that “spring green-up” is largely related to soil temperatures and, to some degree, whether fertilizer was applied in the fall. Fertilizing with the goal of getting the grass to “wake up” sooner will have a minimal effect since soil temperature is the main driver for this.

lawn grass
Spring “green-up” is largely related to warming temperature. Most fertilizing for the year should be done in the fall. Photo: Pixabay

Also, keep in mind that fertilizing in the spring favors more shoot and leaf growth at the expense of root growth. (Fertilizing in the fall tends to favor root growth. Most of the fertilizing for the year should be done in the fall.) Spring fertilization should consist of ~1 lb. nitrogen/1000 sq. ft. total in spring. Using a slow-release fertilizer or splitting applications into two 1/2 lb. rates spaced about one month apart should help to limit excessive growth that could add to the increased mowing frequency often necessary in the spring. Continue reading

What Can I Do About All These Weeds?

Ground Ivy
Ground ivy or creeping Charlie (Glechoma hederacea). Photo by Betty Marose

The famous quotation about the certainties of life which we all know includes death and taxes should also mention weeds! They are sprouting up all over. Even the most meticulously tended landscapes are not immune.

Where to Begin?

The first step is identification. You need to know your opponent. Control is more attainable if you know whether it is a grassy or broadleaf weed. Is it an annual, perennial or biennial? When does it germinate? Fall, spring, or summer?

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Get Your Lawn Back in Shape This September

With summer winding down — nights are getting longer and days getting cooler — September is a perfect time to rejuvenate tall fescue lawns. Aerating and overseeding now in the fall will make your lawn stronger and better able to resist pests and weed encroachment for next season.

Here are a few points to remember when aerating and overseeding for a lawn rejuvenation this fall:

  • The aerator you use makes a difference. A heavier, more powerful (> 5 HP) aerator will be more forceful and more effective in creating deeper cores. Ideally, you should be able to aerify to a soil depth of at least 3-4”.  Equipment rental stores often have suitable aerating machines available. Remember not to go over the lawn too fast and allow the machine to just “bump” along. Travelling slowly and ensuring the area isn’t too dry will help encourage quality cores to be pulled from the soil.

    Lawn aerator
    Aerifying in fall provides more oxygen to the roots and protected holes for new seed to germinate.
  • If you have substantial areas of dead grass or crabgrass weeds, it is probably more effective to remove the dead grass leaves with a hard rake, a “power rake”, or a de-thatcher. The turf seed will need to have good soil contact in order to germinate and grow to provide better coverage. By seeding into an area with a lot of dead debris, the seed may germinate and then dry out – or not “take” at all.

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