Lawns

Q&A: Pros and Cons of the No-Mow May Movement

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Q: Do you have any information related to the “no mow” movement? We have a very weedy lawn and are considering replacing it with Dutch clover. Is that a good idea? Bad idea? 

A: We do not recommend replacing lawn outright with clover. Clover goes dormant in winter, losing leaves, which leaves the soil surface exposed to weed seed colonization and potential erosion. The clovers used in lawns are also non-native and would not support the majority of our native bees (which are specialists, relying on certain native species for pollen, nectar, or plant oils). Generalist bees can use clover or other blooms but these tend not to be the local bees needing the most support from garden plantings.

If you prefer to augment your existing lawn with clover, consider microclover, which is a dwarf and less-aggressive variety of white clover that cohabitates with turfgrass more cooperatively. While not solving any of the other above issues, at least this is a more suitable choice when using clover in a lawn. Our Lawns and Microclover page provides some pros and cons plus links to a more detailed publication (PDF document) about how to go about creating and maintaining this mix.

a flowery lawn with unmowed grasses
Chanticleer’s flowery lawn interpretation, more of a no-mow-ever than a no-mow May situation, and thus of more benefit to wildlife. Photo: M. Talabac

Opinions among professional horticulturists about “No Mow May” actions are mixed because there are both benefits and drawbacks that it creates. You will probably find both proponents and opponents to this practice in Extension and other science-based web publications and articles. The main benefit of the movement is its ability to get gardeners thinking about their landscaping choices and actions and the impacts of these on the ecosystem. (And that’s a good thing!) That said, most of the flowering lawn weeds that no-mow is supposed to protect are non-native and do not support many of our native bees, and allowing them to set seed only enables them to spread further in places where native plants should ideally be growing instead. 

For gardeners interested in having turf serve double-duty as a “bee lawn” – that is, intentionally planted with seed mixtures containing low-growing flowering plants – the benefits and shortcomings of this approach are similar to those with clover lawn conversions or from reducing mowing for limited periods of time. University of Minnesota research shows that bee lawns do provide benefits for pollinators, including native ones. However, most commercially-available bee lawn mixes contain plants from Europe and/or Asia, and are perhaps not the best nutritionally for Maryland’s specialist bee adults or a resource they will be able to use for their young. Some Maryland native plants that can be incorporated into bee lawns, such as Self-Heal (Prunella vulgaris subspecies lanceolata), are not readily available in seed mixes here, and research on Maryland-native plants for use in bee lawns is not available at this time. Visit UMN’s “Planting and Maintaining a Bee Lawn” web page for more detail.

close-up of a purple flowering prunella
purple flowers of prunella
Prunella vulgaris. Photos: M. Talabac

Our energies and efforts aimed at benefiting insects, birds, and other organisms may be better spent creating native plant gardens alongside of (or in place of) lawns, which will not only serve specialist bees more suitably but also will support a variety of other native wildlife in the process. In any garden setting, including when plant selections are native-focused, using a diversity of plant species has several benefits: it can support a greater diversity of wildlife (including pollinators and beneficial insects that help suppress pests), it adds aesthetic and seasonal interest, and it increases the resiliency of the planting as a whole, because different species won’t have the same degree of vulnerability to any one issue (like drought or flooding) that may arise.

white flowers of fleabane in bloom
 Native common fleabane (Erigeron philadelphicus) blooms in a front yard where a portion of the turfgrass was removed and replaced with little bluestem, switchgrass, and a mixture of flowering perennials. Fleabane supports a variety of native bees, solitary wasps, and other beneficial insects. Photo: C. Carignan

Not mowing lawns regularly also stresses the turf by creating a situation where, when mowing does resume, it’s removing much more of the turf’s leaf mass at one time, causing stress and interfering with its normal growth habit that creates a dense lawn. The “grazing response” that mowing triggers, promoting more low growth that fills-in gaps, won’t be happening to the same extent if the grass goes for weeks without being cut, especially as it diverts some energy for growth into producing pollen and seed. (This turfgrass flowering also might be a consideration for people with bad grass pollen allergies.)

This topic of bee resources in lawns as addressed by the no-mow movement is touched upon by wildlife biologist Sam Droege in the native bee special episode of the University of Maryland Extension Garden Thyme Podcast from last summer.

Lawn alternatives, even if not purely native species, are another option when dealing with a lawn that is struggling. While a healthy lawn is providing more environmental services (carbon sequestration, erosion control, nutrient filtering, etc.) than a struggling lawn, if you do not wish to devote resources to improving its health and vigor, then converting those areas to non-lawn is more practical, even if a bit more expensive at first than just rehabbing the lawn. If a tolerance to regular foot traffic from people or pets is needed, then lawn is the best groundcover for this use and you might want to work to improve its health, but otherwise areas not being stepped-on can be planted with other species.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension. Our horticulturists are available to answer your questions online, year-round. You can also connect with your local County/City Extension Office and Master Gardener local programs.

Early Spring Lawn Tips for Fertilizer and Pre-emergent Timing

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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.

The Time to Spring Seed Your Lawn is Now

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With springtime springing, many people are thinking about planting in their yards and gardens. While the best time of year to plant grass seed and renovate is in the fall, we have a narrow window in the spring that can be taken advantage of to try to fill in bare spots and thin areas. Thin or weak areas that may have been damaged over the winter or even last summer are very prone to crabgrass and other weed invasion as we get farther into spring and early summer. With cooler weather forecast later this week (many areas are predicted to have frost in the morning), we still have a good window over the next two weeks for spring grass planting. If you have already applied crabgrass preventer, then you’ll have to wait until fall to plant grass seed, but if you haven’t, now is a good time to try to “thicken up” some weak spots and create more density before weeds have a chance to get a foothold. 

While a “full scale” lawn renovation should only be done in the fall (unless you are using all sod), spring is a good time to rejuvenate thin or weak areas. To do this, use a hard metal rake to remove any dead plant debris from the area and expose the soil. Use a drop spreader or handheld spreader (larger area) or sprinkle seed by hand (smaller area) as you try to get good, even coverage of the area (for tall fescue seed you will want to have about 6-10 seeds/square inch seed density). You can then very lightly rake the area to get the seed worked into the soil less than 1/2″ or carefully step on seeds to ensure good seed-to-soil contact. Next, be sure to cover the seed by topdressing compost or peat moss over the newly seeded area. This will help the seed retain moisture until it starts to germinate and provide some protection from birds. Lastly, try to keep the new seed damp at least until germination. With our cooler weather and a few showers in the forecast, the upcoming weather will help with keeping the seeds moist until they germinate but you may have to do a little watering with your garden hose or sprinkler too. 

We don’t have a big window of time for spring seeding, but seeding now before crabgrass and other weeds become more active later in spring will help increase the density of the lawn and make it better able to resist weed invasion!

By Geoffrey Rinehart, University of Maryland Institute of Applied Agriculture

Lawn and Garden Tips for April

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Wildlife

Eastern box turtle
Eastern box turtle

  • Eastern box turtles and various species of snakes are coming out of hibernation and may visit your yard. Box turtles are becoming scarce throughout much of Maryland because of road mortality and habitat destruction. Observe turtles, but don’t collect them as pets.
  • The eggs of amphibians like wood frogs and toads will hatch in a couple of weeks and produce many small tadpoles. If you need to do some work in your pond, try not to disturb their eggs. Learn more about Creating a Herp Friendly Landscape and Interesting Visitors in Your Landscape.

Houseplants

(Cissus rhombifolia) Oak or grape leaf ivy
(Cissus rhombifolia) Oak or grape leaf ivy

  • This is a good time to re-pot and divide houseplants. Use lightweight, well-drained soilless potting mixes containing peat moss, vermiculite, and perlite.
  • Begin to fertilize houseplants again. The increase in natural light will prompt them to grow.
  • Fungus gnats are small, harmless black flies that hover around, breed in and feed on moist growing media. They can be controlled by being careful not to over-water houseplants. Growing media should be allowed to dry out before watering again.

Lawns

  • LawnThe height and frequency of mowing lawn are very important. Cool season grasses such as tall fescue and bluegrass should be maintained at 3.0 inches for most of the growing season.
  • Keep your mower blades sharp to prevent turf damage. Dry, white, or tan-colored grass blade tips are an indication that the mower blade is dull. Dull mower blades tear turf grass and can lead to disease problems.
  • Leave the grass clippings where they lay. “Grasscycling” eliminates bagging labor and adds organic matter and nitrogen to your soil, allowing you to apply 25% less nitrogen fertilizer.

More tips from the Home & Garden Information Center

The Home & Garden Information Center’s horticulturists are available year-round to answer your plant and pest questions. In addition to gardening questions, we cover houseplants, indoor pests, and more. Send your questions and photos to Ask an Expert!

Lawn and Garden Tips and Tricks for November

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Lawns

  • Typically, November is too late to broadcast lawn seed and expect it to survive the winter. Consider waiting until early spring.
  • This is still a good time to control wild garlic, clover, ground ivy, chickweed, and other difficult weeds with an herbicide if daytime temperatures remain in the sixties. Do not spray herbicides around ponds or on breezy days. Always read and closely follow all label instructions.
  • According to Maryland’s Lawn Fertilizer Law (PDF), the last application of fall fertilizer needs to be applied before November 15th.
  • Lawn info on HGIC

Continue reading →

Lawn and Garden Tips and Tricks for August

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For Ornamental Plants:

  • Late August through September is usually a good time to transplant, divide and plant perennials such as daylily, liriope (photo left), and echinacea.  Be sure to keep them well watered during dry periods.
  • Annuals and perennials, like yarrow and salvia, may have grown spindly and are not flowering well. Cut them back to encourage re-bloom. Deadhead the spent blooms of annuals like zinnias and marigolds. This will encourage them to continue blooming more vigorously.
  • Plant hardy mums for fall color this month so they will become well established prior to the winter.

More August ornamental tips

For Lawns:

  • In dry periods grasses go dormant but recover when rain returns. Newly seeded or sodded lawns may actually be dead and will need to be reseeded.
  • Mid-August through mid-October is the best time to start new lawns and renovate or overseed existing lawns. We recommend a turf-type tall fescue cultivar at a rate of 4 lbs. of seed per 1,000 sq. ft. of area for overseeding, or 8 lbs. per 1000 sq. ft. for new lawns.
  • If your lawn area contains more than 50% weeds, consider a total lawn renovation. Newly seeded turf must be watered regularly. See Starting a New Lawn.

More August lawn tips

Outdoor Insects:

  • You may notice the European hornet stripping the bark off shrubs (especially lilac) and trees. This stripping of the bark is usually minor and does no real harm to a shrub or tree. The European hornet is a large yellow and brown hornet (photo) that nests in cavities in trees, stumps, wood piles, sheds, etc. and feeds on insects. Unlike most other wasps and hornets this one is a night flyer.
  • Do not spray pesticides in your garden unless you’ve observed a particularly serious pest and the damage caused by the pest. Follow all label directions. Always select the shortest residual, least toxic insecticide to avoid killing beneficial insects.
  • Avoid mosquito and midge problems by turning over any pots, lids or saucers that might collect water and create a breeding site. Also check clogged house gutters another favorite breeding place for mosquitoes and midges. Many people use corrugated drain pipe attached to downspouts to help move water away from their homes. The corrugations hold water and are a prime place for tiger mosquitoes to breed. To avoid the problem, use a smooth drain pipe or securely attach the corrugated drain pipe to the downspout and cover the open end with a piece of pantyhose secured with a rubber band. This will keep adult female mosquitoes and midges out of the drain pipe.

More August indoor and outdoor insect tips