Q&A: When Should I Prune Shrub Roses?

Shrub rose pruned back in early March. Photo: M. Talabac

Q:  When do I prune shrub roses? Is now okay? How far back do I cut?

A:  Although you probably won’t kill a plant by doing it now (November) it’s best to wait until late winter or early spring (late February to early March time frame for central Maryland). Pruning before the dormant season might reduce some winter hardiness, potentially contributing to stem dieback. If you pruned in fall and a drastic cold snap were to cause plant tissue damage during the winter, then the second trimming to remove the dead wood would shorten the stem even more, as opposed to delaying trimming until the worst of winter is past and only making one trim at the height you prefer.

The height to reduce the stems depends on personal preference, and recommendations vary, but one convention is to cut shrub rose stems down to about 15 or 18 inches off the ground, though you could go lower to 12 inches or higher to 24 inches. Roses bloom on new growth (except for many climbing roses that also flower on old growth), so pruning at the end of winter will not remove flower buds. If you delay pruning into April or so, though, you might postpone when those first flowers of the season appear.

If a rose is so rangy that it’s just in the way, like arching over a sidewalk or blocking a hose spigot, you can compromise and make a light trim now to tidy it up so the thorns don’t catch people and then do the main pruning in several months.

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 ExtensionOur horticulturists are available to answer your questions online, year-round.

What’s Eating My Rose Leaves?

roseslug sawfly damage on rose
Roseslug sawfly damage on rose. Photo: UME/Ask an Expert

Q: My rose leaves have white spots and holes in them. What causes this and how do I treat it? Is there a natural remedy that does not involve powerful chemicals?

Answer: It looks like your rose has symptoms of sawfly damage. Check the undersides of the leaves and look for tiny green larvae that look like little worms or caterpillars. These are the juvenile stage of an insect called roseslug sawfly.

Roseslug sawflies are neither slugs nor flies. They belong to the same order of insects as wasps, bees, and ants (Hymenoptera). Adult female sawflies use their unique ovipositor (egg-laying part) to saw a small slit in a leaf or stem where they lay their eggs. When the eggs hatch, the larvae feed on the leaf surfaces and cause an etched or scratched appearance. Some roseslug larvae chew through the leaves entirely. Damaged foliage turns brown and curls up as the season progresses.

bristly roseslug on rose leaf
Bristly roseslug (Cladius difformis). Photo: Whitney Cranshaw, Colorado State University, Bugwood.org
bristly roseslug sawfly adult
Bristly roseslug (Cladius difformis), adult stage. Photo: Whitney Cranshaw, Colorado State University, Bugwood.org

In Maryland, there are three species of roseslug sawflies that cause damage to roses: the bristly roseslug sawfly, the roseslug sawfly, and the curled rose sawfly. Most of the feeding activity on roses in Maryland is seen in May and June, but some sawfly larvae can continue to be active until fall. Other insects, such as Japanese beetles, also cause chewing damage on rose foliage (typically in June-July).

Browning and leaf curling from rose slug sawfly damage. Photo: UME/ Ask an Expert

The best way to manage roseslug sawflies without chemicals is to monitor your plant(s) for damage symptoms early in the season (start looking in May) and manually remove any larvae (squish them or pick them off and discard them). A forceful spray of water from a garden hose targeted toward the leaf undersides can also get them off. Once dislodged, they cannot climb back up into the plant. Horticultural oil and Spinosad also work well against sawflies. Read and follow the product label instructions for the correct application procedures.

Two sawfly larvae are present on the undersides of rose leaves. Photo: C. Carignan

Predatory insects and birds help to manage sawfly populations naturally. Adding more flowering plant diversity to your landscape will provide food and habitat for beneficial animals that in turn help to reduce future pest problems.

Rose shrubs usually recover from sawfly damage eventually, as long as they are not struggling from other ailments or stressors such as drought.

Additional Resources

Sawflies | UME Home & Garden Information Center

Rosie Defoliators | Bug of the Week, University of Maryland, Department of Entomology

By Christa Carignan, Maryland Certified Professional Horticulturist, Coordinator, University of Maryland Extension Home & Garden Information Center. Read more by Christa.

Have a plant or insect question? University of Maryland Extension’s experts have answers! Send your questions and photos to Ask Extension.

Q&A: Do Beetles in Old Wood Harm Trees?

a black beetle on a log - bess beetle
Patent-leather beetle on a rotting log. Photo: M. Talabac

Q:  I found several of these beetles in an old decaying stump and am concerned for my healthy trees. Will they attack live trees?

A:  No, these beetles feed on rotting wood and the fungi decaying it, and they pose no threat to other trees. Several common names are given to them: Patent-leather Beetle, Bess Bug, and Horned Passalus.

These insects have a rare life history in that they live in groups and provide parental care for their larvae, feeding them pre-chewed rotting wood, likely for over a year while the young mature slowly.

The feature I find the most entertaining about them is their ability to squeak. Both adults and larvae can stridulate, which means they use one body part to rasp against another to create noise. The purpose of this is probably to communicate with each other. Cricket chirping and katydid calling are forms of stridulation, but in the case of these beetles, it produces more of a high-pitched sound akin to a person making “kissy” noises at a pet.

Interestingly, Iowa State University’s BugGuide web page for Bess Beetles speculates that the “bess” part of its name might derive from baiser, French for “to kiss.” (Or it’s derived from the fact that their forward-facing jaws can pinch, though I’ve never been bothered and I pick up these beetles every time I see them because they’re fun to find. “Petting” them sometimes makes them stridulate, which is always endearing.)

Wood-recycling insects like these are great to have around and rarely if ever pose a risk to healthy plants. Not only do they get those old stumps and logs out of the way for free (even though it can take a while), but both they and the fungi they work with are a means to make the old tree’s nutrients available again to the rest of the ecosystem.

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 ExtensionOur horticulturists are available to answer your questions online, year-round.

Nurture Natives: 4-Hers Take a Stand to Protect Maryland’s Ecosystems, Economy, and Agriculture

This is a guest post by Esther Bonney, a student in Charles County, Maryland, and a member of the University of Maryland Extension 4-H Program.

Invasive plants are detrimental to Maryland’s well-being, and their damaging effects are becoming more evident each year as we witness declines in crop productivity, reductions in pollinators critical to maintaining stable ecosystems, and widespread displacement of native habitats. Between 2008 and 2013, wild bees declined by 23 percent across the U.S.—a serious concern to farmers and consumers alike. Through educational programs, guides, and native giveaways, Nurture Natives is taking a stand against invasive species to protect native plants and pollinators, restore natural habitats, and support farmers. Nurture Natives is led by University of Maryland 4-Hers Esther Bonney and Samantha Rutherford and Extension 4-H Educator Amy Lang and UME Charles County Master Gardener Marlene Smith. 

people line up for native trees at Maryland Day
Visitors line up for native trees at Maryland Day, stretching down the courtyard and around the sidewalk, sometimes longer than the line for free ice cream!

In March 2022, our team was selected to attend the National 4-H Youth Summit on Agriscience. There, we developed our project, Nurture Natives, to address a prevalent agricultural issue in our community: invasive plant species. Invasive plants choke out native species and are a major cause of crop loss and food insecurity. Invasive trees such as the Tree of Heaven rapidly overtake farmlands and attract invasive pests such as the Spotted Lanternfly, which is a serious threat to grape crops. In the U.S. alone, invasive species cause $40 billion worth of production losses to crops and forests per year. 

Nurture Natives is dedicated to increasing biodiversity through the planting of native trees and the eradication of invasive plants. In the past year, Nurture Natives has been featured on the National 4-H and University of Maryland Extension websites, won a Lead to Change Grant, and was selected by the National 4-H Council as one of two projects nationwide to receive the highly-competitive Scale for Success Award. Nurture Natives was also recently featured in the Southern Maryland Independent: Nurturing natives and the next generation of environmental scientists

Our team began our work by educating and raising awareness about invasive species in our community of Charles County. We hosted educational programs at schools and camps and, in October 2022, partnered with eight local organizations to host the first annual Nurture Natives Giveaway. We hosted games, crafts, presentations, and a honey-tasting to showcase the importance of native species and pollinators. In just two hours, we distributed 150 native trees and shrubs and reached over 70 families. 

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Azaleas and Home Gardens

Spring is incomplete without the bold and soft hues of azaleas in your home garden. These spectacular plants are prevalent and have dominated yards and countless gardens in North America. These plants originated in Asia and made their way to the US via Europe around two hundred years ago. Since then, according to the American Azalea Society (ARS), over 10,000 different cultivars, or cultivated varieties, have been registered or named. The high demand for cultivated azalea can be attributed to its small manageable dwarf sizes, diverse attractive colors, deep green leaves year-round, and adaptability to the climate, making them easy to grow.

However, there are equally beautiful native azaleas in North America that are seldom seen in home gardens and are still not as well-known as their Asian cousins. To find them, it would be best to wander from the landscaped yards into the woods. In this post, I talk about the extraordinary beauty and ecology of native azaleas, as they require more attention and care from the gardening community.

What are native azaleas?

Azaleas are members of the heaths (Ericaceae) plant family, which includes cranberry, blueberry, and huckleberries. Because there is often confusion among people between azaleas and rhododendrons, it is much easier to remember that all azaleas are rhododendrons, but that all rhododendrons are not azaleas. In fact, azaleas belong to the genus Rhododendron. Azaleas native to North America are usually medium-sized or tall shrubs with soft, deciduous leaves, funnel-shaped flower lobes, and long tubular flowers with stamens extending beyond their showy petals. There are eighteen North American native azaleas (visit the American Azalea Society and American Rhododendron Society to learn more).

Why grow native azaleas?

Native azaleas display shades of white, orange, pink, red, and yellow throughout the spring and summer. Although most people associate azaleas with spring, several native ones bloom in mid and late summer. It is often noticed that azaleas in their natural habitat show some staggering in their flowering timing, and their flowering durations usually range between 15 to 20 days. So, if you carefully select species based on their flowering timing, you can have azaleas bloom in your home gardens for at least four to five months. Unlike the evergreen cultivated ones, native azaleas have exceptional fall color before they shed their leaves for winter. Most native Azaleas can reach heights of 4’-8’ and can be used in hedgerows and as the background to other flowering dwarf shrubs. Some of the common native azaleas in the woodlands of Maryland, Virginia, and DC are smooth azalea (Rhododendron arborescens), swamp azalea (Rhododendron viscosum), pinxter azalea (Rhododendron periclymenoides), coast azalea (Rhododendron atlanticum) and early azalea (Rhododendron prinophyllum).  

Besides the colorful hues in your green space, growing azaleas will also help maintain the native pollinator network in your local environment. Native azaleas can sustain a variety of fauna through their flowers; they are attractive to bees, butterflies, moths, and hummingbirds. The quantity and quality of nectar and pollen among these plants are often observed to be higher than in the cultivated ones. In general, they have a high amount of concentrated nectar and string-like pollen threads that help attract myriad forms of floral visitors native to North America.

Some azalea species have attractive warm orange and red flowers, and birds can detect warm colors easily. At the same time, insects, including bumblebees and smaller bees (e.g., Andrena sp.), are attracted to light pink, purple, and white palettes. Certain native species, such as sweet azalea and piedmont azalea, have a strong sweet fragrance. Besides providing a sweet smell, their fragrance also helps attract night pollinators such as moths. Nectar volume among the azalea flowers is relatively low compared to its nectar concentration; therefore, the migratory ruby-throated hummingbird makes occasional visits, as birds usually prefer flowers with high voluminous nectar. Their unique floral characteristics also attract diverse butterflies, recognized as potential pollinators for these species. Commonly observed butterflies are eastern tiger swallowtails (Papilio glaucus), silver spotted skippers (Epargyreus clarus), and great spangled fritillaries (Speyeria cybele). The flapping of butterfly wings helps transfer pollen from the male to the female organ and facilitates successful reproduction in these plants. Therefore, growing different shades of native azaleas in your yards and home gardens will be a good idea to support native pollinators.

Native azaleas are also relatively free of pests and diseases compared to cultivars, making them low-maintenance plants. They do not require regular pruning and are moderately slow growers. However, knowing the ecology of these species may be helpful for plant growers. For example, in the forest, these plants are mostly found as an understory of other tall hardwood trees like oaks and chestnuts; therefore, they will do well in less light and shaded areas in the home gardens. Most of them require moisture with good drainage and humus-rich acidic soil. You can learn more about the detailed requirements of the conditions preferred by these plants at the American Azalea Society.

It is never too late to add these cool plants to your home garden.

By Shweta Basnett, Fulbright Postdoctoral Fellow, Department of Entomology, University of Maryland. Visit her website for more information about her current research.


Native Plants Add Beauty and Support Wildlife 

wild bergamot flowers are lavender color
Native wild bergamot (Monarda fistulosa) attracts pollinators from butterflies to hummingbird moths and is both deer and rabbit-proof. Photo: Elmer Verhasselt, Bugwood.org

I love native plants. I garden for beauty and wildlife and nothing supports healthy habitats better than native plants. 

So what are native plants? They are beautiful, resilient plants that naturally occur in an area.

Having evolved over millennia with native wildlife, they naturally support them best. A native white oak supports 557 species of butterflies and moths while a non-native gingko tree supports just five.  

So if you want to support bees, butterflies, and beneficial insects that help control pests, native plants are the way to go. 

They also support larger wildlife such as birds with their seeds, fruit, shelter, and places to raise young. Again, native plants evolved with them, so they naturally provide what they need.  

According to conservationist, author, and entomologist Doug Tallamy who penned the bestsellers “Bringing Nature Home” and “Nature’s Best Hope,” native plants support 29 times more wildlife diversity than non-native plants.  

Well adapted to our soil and climate, native plants are resilient with a capital “R.” They’ve persisted through many hot, dry, wet, and cold years, surviving all previous climate change that has occurred, positioning them well to adapt to future changes. 

Adapting over eons makes you tough. Native plants have fewer pest and disease issues and some have deep roots which make them drought resistant. That means less watering, fewer chemicals, and a healthier landscape. 

Did I mention how beautiful they are? There is a nasty rumor out there that native plants are weedy. Bosh and balderdash.   

Native coral honeysuckle trumpets red/yellow/orange flowers that welcome hummingbirds. Threadleaf coreopsis wafts a riot of petite yellow daisies in a drift of lacy foliage.  

Wild blue indigo sports 4-foot stems of deep blue sweet-pea-like blooms. Cardinal flower flashes brilliant red and is a magnet for hummingbirds and butterflies.  

Bees love to rummage among the pure white blossoms of native foxglove. And goldenrods carousing with purple asters are the very definition of fall beauty.

Don’t get me started on native trees and shrubs. I love ninebark’s white pompoms, the red dangling fruit of chokeberry, the deep maroon flowers of Carolina allspice (native from our South), skinny willow oak leaves, and the giant leaves of pawpaws

red flower of Carolina allspice
Carolina allspice (Calycanthus floridus). Photo: Miri Talabac

How can you find out what native plants might work in your landscape?  

Discover many resources – including recommended native plants for Maryland on our website and on the Maryland Native Plant Society website.

My favorite native plant reference, “Native Plants for Wildlife Habitat and Conservation Landscaping,” has color photos and plant profiles. Download it for free.

Where do you find native plants? Visit your favorite garden center. Native plants are becoming more common. If they’re not there, ask. Nurseries grow and buy based on client interest.  

The Maryland Native Plant Society website also lists native plant sales and nurseries on their website.

Many Master Gardener groups – including ours – hold spring plant sales that include native plants. Contact your county/city coordinator to learn if one is scheduled near you.

I hope I’ve encouraged you to include some native plants in your landscape to add beauty, invite wildlife and support a healthy ecosystem.  

By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension. This article was previously published by Herald-Mail Media. Read more by Annette.

Fruit Trees & Small Fruits: The Garden Thyme Podcast

Listen to the podcast

In this month’s episode, we’re talking about selecting and growing small fruits and fruit trees. With spring blooming around us, many garden centers and stores will have fruit trees and small fruit shrubs for sale. Creating a home orchard can provide a source of delicious fruit. However, fruit trees and shrubs have their own unique challenges. In this month’s episode, we discuss tips for planning your orchard, growing small fruit (~11:05), tips for growing tree fruit (~27:53) and native fruits (~38:15). 

We also have our: 

  • Native Plant of the Month – Serviceberry (Amelanchier spp.) ~43:30
  • Bug of the Month –  Plum Curculio ~47:30
  • Garden Tips of the Month – ~52:38

We currently have an open survey for ALL listeners; whether you’ve listened to all of our episodes, or this is your first time. We developed an evaluation to find out if the information we share on the podcast has made a difference in your practices at home. We promise that it is a short, easy 5-minute survey, and we even have exclusive podcast stickers to give to those who participate. We are so thankful for the feedback, and we appreciate you tuning in for the podcast! 

You can take our survey here.

If you have any garden-related questions, please email us at UMEGardenPodcast@gmail.com or look us up on Facebook. For more information about the University of Maryland Extension (UME) and these topics, please check out the UME Home and Garden Information Center.

The Garden Thyme Podcast is brought to you by the University of Maryland Extension. Hosts are Mikaela Boley- Senior Agent Associate (Talbot County) for Horticulture, Rachel Rhodes- Agent Associate for Horticulture (Queen Anne’s County), and Emily Zobel-Senior Agent Associate for Agriculture (Dorchester County).

Theme Song: By Jason Inc