lawn care

A Lawn Retrospective on the Summer of 2023: Looking Ahead to the Fall Season

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Many lawns showed drought-stress symptoms in early summer. Photo: M. Talabac, University of Maryland Extension (UME)

It seems like ages ago, but during late spring and early summer we were in the midst of a long dry spell–and then things changed! Many areas in the region have seen more typical summer rainfall since late June. Since then, summer annual weeds and sedges were given new life with all of the wet conditions. For many homeowners, it has been a difficult summer keeping weeds like kyllinga, nutsedge, and crabgrass at bay during the wet, humid weather.  

Crabgrass and thin spots in a lawn. Photos: C. Carignan, UME

University of Maryland research (and others) has indicated that the best way to deter crabgrass is to mow higher. Experiment plots mowed in the 3.5-to-4-inch range have consistently had less crabgrass invasion than plots mowed at 2 or 3 inches. While this late summer weather has led to a lot of crabgrass and sedge invasion, homeowners can take solace in the fact that relief is in sight as far as the calendar is concerned. Late August/early September is the perfect time of year to re-seed with cool-season grasses like tall fescue to undertake a full-scale renovation or a lawn “rejuvenation.”

First, let’s define a few terms:

Complete renovation involves killing the existing sod to bare soil and re-seeding or installing sod.

Overseeding involves using an aerator or de-thatcher to open up the turfgrass canopy and then applying seed to increase density and sustain the stand. 

Repairing bare spots involves raking up old debris by hand or loosening it with a de-thatcher, then seeding.

More detailed information on these techniques can be found on the University of Maryland Extension Lawn Renovation and Overseeding resource page.

How do you decide what to undertake? If your lawn is thin, overrun with crabgrass, has a high percentage of broadleaf weeds, or is an otherwise “unsalvageable mess” you would probably consider a full renovation. If your lawn is a little weak in places, but otherwise dense and relatively healthy, overseeding would be more appropriate. Ensuring good “seed to soil” contact and maintaining adequate moisture in the seedbed is critical for successful germination.

Another key element in lawn renovation and overseeding is seed selection. There are a number of varieties (cultivars) of tall fescue available, however, some have performed better than others in the UMD evaluation trials and these are listed as “recommended varieties” in UMD Extension Bulletin TT-77-Recommended Turfgrass Cultivars (PDF). Although these varieties may be difficult to find at “big box” stores, many local garden retailers seek them out to stock them, and homeowners can often purchase them from local landscape professional suppliers or find them online at sites like seedsuperstore.com.

By Geoffrey Rinehart, Senior Lecturer, Turfgrass Management, Institute of Applied Agriculture, University of Maryland. Read more articles by Geoff.

Spring Lawn Care Tips

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A healthy, dense-growing lawn will do a better job of minimizing weeds and reducing erosion compared to a lawn that is thin and weak. For a variety of reasons, lawns can be challenging to grow in Maryland’s transition-zone climate. Turfgrass requires regular maintenance. Here are some steps you can take in the spring to keep it healthy, without resorting to “weed and feed” products. This series of videos is presented by Geoffrey Rinehart, Lecturer in Turfgrass Management at the Institute of Applied Agriculture, University of Maryland.

Mowing Tips to Prevent Weeds and Diseases
Winter Annual Weeds
Using Slow-Release Fertilizer

Summer Lawn Woes: Reasons Why Tall Fescue Grass Declines at This Time of Year

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It seems like a while ago, but it was only 5 weeks ago that we were experiencing a fairly gentle start to summer. We even had a few days in June with highs in the 60’s and it made for pretty easy lawn growing weather.

Flip the calendar to mid-July and it has been a different story. All of us knew summer would arrive eventually, and now we are dealing with high temperature and high humidity conditions very typical of mid-summer in Maryland.

For those with warm-season grass lawns, like zoysiagrass, the lawn should be thriving, as these grasses enjoy the heat. For most homeowners who have tall fescue, summer is always a challenge to minimize the heat stress and disease pressure on the lawn. Tall fescue is best adapted to growth when low temperatures are in the 50’s and highs are in the 70’s to around 80. Through July, we have had many days near or above 90 and many nights where the temperature didn’t drop below 70.

drought stress symptoms on tall fescue lawn
Drought stress symptoms appearing in tall fescue lawn. Drought-stressed plants exhibit a purple to grayish hue. Photo: Geoff Rinehart

There are a few different reasons your tall fescue lawn may be going brown or declining this time of year—the most common are related to drought stress, soils that are too wet, or brown patch disease. Typically, growth slows down a bit in mid-summer anyway as part of a grass’s natural growth cycle as it uses more carbohydrates (food reserves) than it makes. So when the grass does experience stress or disease it is slower to recover. Drought-stressed plants exhibit a purple to grayish hue, a narrower or “curled up” leaf blade, and footprints are visible for several minutes after walking across a drought-stressed area. Continue reading →

Spring Lawn Care Tips & Bay-Friendly Lawn Workshop

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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 →

Q&A: Tire Gouges in a Lawn and Planting Grass After Construction Work

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lawn with tire gouges
University of Maryland Lecturer and Turfgrass Management Advisor Geoff Rinehart answers your questions about lawn care and planting. For more Maryland lawn care information, see the University of Maryland Extension Home & Garden Information Center website.

Q: I had a new shed put on my property. The delivery driver had to back onto my lawn. The weight of the truck and the flatbed put an initial 2-3 inch depression in the lawn. Where the driver had to pivot the trailer, the flatbed tires dug into the lawn 3-4 inches. In order to recover the contour of the lawn and deal with the gouges, what steps do you suggest I take? Today, after it rained all day, I went out on the lawn and attempted to press the humps down with my body weight and somewhat level the lawn back. I am worried, though, that the depressions indicate a serious compaction of the soil and damage to further propagation of the lawn.

Answer: You are correct – the gouges made by the flatbed have likely caused serious compaction to the area. You can try to press the gouges back into place and aerify now and topdress with ½” topsoil to try to smooth things out and see what happens next year. If you notice the area is struggling compared to the rest of the lawn and drying out more quickly if we have a dry summer, you’ll probably want to renovate the affected area by rototilling, re-grading, and re-seeding.   Continue reading →

Q&A: Japanese Stiltgrass Management and Lawn Fertilization Tips

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University of Maryland Lecturer and Turfgrass Management Advisor Geoff Rinehart answers your questions about lawn weeds and fall fertilization.

Q: What is this “grass” and is it possible to eradicate it from our lawn? It has been spreading down the hill from our neighbor’s property. What’s the best way to bring our lawn back to a nice quality grass?

Japanese stiltgrass in a lawn

Answer: Japanese stiltgrass (Microstegium vimineum) is an invasive summer annual grass that is becoming more pervasive in Maryland. While it used to be more limited to just woodland areas, we are getting more reports of it infesting lawn areas in recent summers.

As is the approach with any weeds, practicing good turfgrass cultural practices to encourage a healthy, dense stand of grass is the cornerstone of any lawn management program. Mowing taller (3”-3 ½”), fertilizing based on University of Maryland recommendations, and overseeding annually with improved turfgrass cultivars are three practices that will help create greater density.

This summer has been a particularly difficult one for controlling summer annual grasses like crabgrass, goosegrass, and, of course, Japanese stiltgrass since these weedy grasses are favored by wet, hot conditions like the weather we had in July-September. Since Japanese stiltgrass is a summer annual, it can be deterred by applying a pre-emergent herbicide in the spring at forsythia bloom (which is a similar approach to crabgrass control). When watered-in, pre-emergent herbicides form a soil barrier to seed germination. However, most of these products only last 6-10 weeks (the lower part of this range when it is wet and/or hot, the upper part when it is dry and/or cool). This May was rather rainy, so if you applied a pre-emergent in early April, another should have been applied in June. Usually, two applications are enough to get us to early August and then summer annual weed pressure decreases as early cooler weather is usually a month around the corner.  Continue reading →

A Lawn Retrospective on the Summer of 2018: Looking Ahead to the Fall Season

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nutsedge and crabgrass in a lawn
Nutsedge and crabgrass have been particular challenges this year with all of the late summer rain.

It seems like ages ago, but during late spring and early summer we were in the midst of a long dry spell–and then things changed! It seems once the rain started it hardly ever stopped during late July and early August and all of this rain created its own set of problems. In particular, summer annual weeds and sedges were given new life with all of the wet conditions. For many homeowners, it has been a difficult summer keeping weeds like crabgrass, Japanese stiltgrass, kyllinga, and nutsedge at bay during the wet, humid weather. Even folks who had applied a second application of pre-emergent herbicide in late spring were seeing that product break down more rapidly with the inordinate amounts of rain the region experienced.

University of Maryland (UMD) research (and others) has indicated that the best way to deter crabgrass is to mow higher. Experiment plots mowed in the 3½-4” range have consistently had less crabgrass invasion than plots mowed at 2” or 3”. While this late summer weather has led to a lot of crabgrass and sedge invasion, homeowners can take solace in the fact that relief is in sight as far as the calendar is concerned. Late August/early September is the perfect time of year to re-seed with cool-season grasses like tall fescue to undertake a full-scale renovation or a lawn “rejuvenation.” Continue reading →