overseeding

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 & Bay-Friendly Lawn Workshop

Maryland Grows2 Comments

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 →

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

Maryland Grows3 Comments

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 →

Spring Lawn Care: How to Deal with Weeds and Bare Spots

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forsythia shrub in bloomWith spring gardening season right around the corner, lawn questions have been rolling into the Home & Garden Information Center (HGIC). Here I’ll address some of the most common questions about weeds and overseeding.

Dealing with Winter Weeds

chickweed
Chickweed

In late winter/early spring, we typically see winter annual weeds in thin, under-fertilized, wet, or shady areas. These weeds germinated in the fall and will die as the weather warms up later in the spring. In my observations, this has not been a particularly bad year for winter annuals. They are favored by wet, mild winters and I think we had just enough “bitter cold” in January and a fairly dry stretch through December and January to reduce populations.

Typical winter annual weeds include chickweed, henbit, purple deadnettle, and shepherd’s purse. Options to address these winter annual weeds include hand pulling, spot spraying with a broadleaf herbicide, or waiting until they die once weather climbs to the 60’s and 70’s on a regular basis. For perennial weeds like dandelion which will start to re-emerge later this month, hand-pulling or spot spraying are the best methods for control.

Continue reading →

Fall Tips for Lawn Renovation: Next Steps

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Warm early October weather has extended the “overseeding window” for fall lawn care. While the first week in October is usually the traditional cutoff for establishing new lawns or rejuvenating existing lawns, the warm early October weather has extended the window by 1-2 weeks.

You can read my September blog post for more information on overseeding and you can still do it, but this follow-up post will deal more with a question that has been coming into the Home & Garden Information Center as of late: “I established a new lawn (or overseeded) in September and some weeds are starting to come up — now what?” Continue reading →

Get Your Lawn Back in Shape This September

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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.

Continue reading →