Author:Christa

Great Grasses for Maryland Landscapes

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What are some beautiful plants that are relatively easy to maintain and unappealing to deer? Take a look at the ornamental and native grasses!

Ornamental grasses are plants that provide year-round beauty, texture, persistent ground cover, erosion control, and a variety of additional benefits. They are:

  • Available in many heights and forms suitable for different landscape situations
  • Helpful in trouble spots like slopes or places where a living screen is desired
  • Relatively easy to maintain by pruning back once each year
  • Generally distasteful to deer.

If you are planning to add native plants to your landscape, add a few grasses to the mix. Grasses provide winter shelter for beneficial insects and seeds for birds. Some even have interesting associations with small butterflies called skippers. For example, the Leonard’s Skipper uses little bluestem, switchgrass, poverty oatgrass, and bentgrass as host plants. That means that when these insects are in their juvenile stage (caterpillars), they can only feed on these types of grasses to survive. As adult skippers, they fly off to feed on the nectar of other flowering plants. They are delightful to watch “skipping” around a butterfly garden!

ornamental grasses in winter
Ornamental grasses provide textural interest in a garden in the winter. Here they are beautiful in combination with remnant seedpods and the red berries of winterberry holly in the background. Photo: C. Carignan

There are about 350 species of grasses in Maryland. They are the primary plants found in native meadows and there are even grasses, such as Eastern bottlebrush grass (Elymus hystrix), that thrive in our state’s shaded woodland areas.

Eastern bottlebrush grass
Eastern bottlebrush grass (Elymus hystrix) Photo: Chris Evans, University of Illinois, Bugwood.org

The Maryland Native Plant Society has named 2020 “The Year of the Grasses”. All year long, through their monthly events and plant walks, you can learn about Maryland’s grasses and their native habitats.

Ornamental and native grasses are readily available at garden centers and native plant sales. Be sure to avoid invasive ones like Chinese silvergrass (Miscanthus sinensis).

switchgrass
Switchgrass (Panicum virgatum) ‘Shenandoah’. Photo: Mikaela Boley

For some great choices, check out my colleague Mikaela Boley’s excellent guide to Ornamental and Native Grasses for the Landscape on the Home & Garden Information Center website.

If you already have ornamental grasses in your landscape, now is a good time to prune them. Grasses that turn brown in the winter should be cut down to about 2″ above the ground in early spring before new growth begins.

By Christa K. Carignan, Coordinator, Digital Horticulture Education, University of Maryland Extension Home & Garden Information Center. Read more posts by Christa.

Helen’s flower hails pollinators

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common sneezeweed flowers
Helenium autumnale. Photo: Beverly Turner, Jackson Minnesota, Bugwood.org

Helen’s flower is an underdog when it comes to native plants. It is not as well known or as popular as butterfly milkweed, bee balm, or black-eyed Susans — but perhaps it’s time for its day in the sun. It makes a nice addition to a pollinator garden.

Helenium autumnale is the species name of this North American native perennial plant. It goes by the (somewhat unfortunate) name of “common sneezeweed” because dried parts of the plant were formerly used for making snuff to induce sneezing. As an ornamental garden plant, it is not known to prompt sneezes from pollen dispersal (it relies on insects for pollination) and I prefer to address it by its lovelier common name, Helen’s flower… or just plain Helenium.

Wild Helenium autumnale boasts cheerful yellow button-like flowers tended by a skirt of turned-down petals in late summer to fall. Its natural habitat in Maryland includes swamps and moist riverbanks, so in your garden, it will like a location where it has some regular soil moisture. It can grow in full sun or partial shade and stretches in height from 2 to 5 feet tall. The flowers support a variety of pollinators such as bees, wasps, syrphid flies, butterflies, and beetles.

A wide variety of cultivars of Helenium are now available. They range in color from bright canary yellow to orange and crimson and various combinations in between. Many of the cultivars tolerate drier soil and have a more compact habit.

Mt. Cuba Center in Delaware conducted field trials of 44 Helenium species and cultivars from 2017 to 2019. They evaluated plants for their habit, vigor, disease resistance, floral display, and pollinator visits.

helenium flowers in a garde
Helenium flowers in a garden, “The warm glow of early Autumn” by hehaden, Flickr

Given the high interest in pollinator gardens right now, I was curious about their observations of pollinator visits in particular.

The native Helenium autumnale had the most observed pollinator visits (162), while the cultivar H. ‘Zimbelstern’ came in second (151). Both of these had excellent powdery mildew resistance as well. Other cultivars such as Helenium autumnale ‘Can Can’ and H. ‘Tijuana Brass’ also had excellent ratings for these two characteristics. The best performers in the study overall (considering all the characteristics evaluated) were ‘Kanaria’, ‘Zimbelstern’, and ‘Can Can.’

The native Helenium autumnale had the most observed pollinator visits (162), while the cultivar H. ‘Zimbelstern’ came in second (151).

For all the details and results of the evaluation, read the report online.  

If you plan to start (or add to) a pollinator garden this spring, do consider adding Helen’s flower if you have a moist site in full sun or partial shade. Mt. Cuba’s report provides good information on plant care, including staking and pruning tips and recommendations for managing the two most common diseases — powdery mildew and aster yellows.

To purchase plants, check the Maryland Native Plant Society’s website for spring native plant sales and nursery sources.

Visit the Home & Garden Information Center website for additional resources on native plants and gardening for pollinators.

By Christa K. Carignan, Coordinator, Digital Horticulture Education, University of Maryland Extension Home & Garden Information Center. Read additional posts by Christa.

Q&A: Can you recommend apps or websites for plant identification?

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taking a cell phone photo of a plant
A well-focused photo of a flower can be uploaded to an app for identification. Photo: Dan Adler

Q: Can you recommend apps or websites to help with plant identification?

A: The Picture This app does a good job with basic plant identification and works both on iPhone and Android. Take a good clear photo of any distinguishing features of your plant (e.g., flowers, fruits, leaf arrangement) for the best results. When you upload your photo to the app, it uses artificial intelligence technology to compare the details of your plant to those in its database of 10,000+ species. It will come up with the most promising matches within seconds.

In my experience, Picture This is not always accurate, but it does well most of the time. It is the best app I have found for plant identification. It will often get you to the correct plant family or genus, if not the exact species. The app also provides information about growing conditions and care tips for your plant.

Another good app is iNaturalist. This app was developed jointly by the California Academy of Sciences and the National Geographic Society and also works both on iPhone and Android. It has a large community of users, including scientists who contribute to it and use some of the data for their research.

taking a photo of a leaf with phone

Similar to Picture This, you can submit your photos to iNaturalist and the app searches a database to find the best match. You also can crowdsource an answer by asking for help from people who use the app. Knowledgeable members of the iNaturalist community will identify and verify your observations. In addition to plants, iNaturalist identifies insects, birds, other animals, and even fungi.

There are basic videos online to help you learn how to use the features of iNaturalist. Some nature centers and community groups occasionally offer hands-on workshops to learn and practice using the app. For example, if you are in the vicinity of Montgomery County, Maryland, the Maryland Native Plant Society’s January 28, 2020, meeting in Kensington will focus on how to use some of the more advanced features of iNaturalist (Discover the Full Capabilities of iNaturalist).

In my experience, Picture This has been more accurate with plant identification whereas iNaturalist is stronger for identifying insects and other animals. Since these tools are still developing, it is a good idea to check the results with another reference to verify the identification. For example, you can submit your photo(s) to the Home and Garden Information Center’s Ask an Expert team if you would like further assistance or more information about our local plants in particular. As more people use and contribute to plant identification apps, surely they will improve and become more refined.

potted plant and a laptop computer

There are also several Facebook groups that are helpful for identifying plants. The ones I have found most useful are Plant Identification, Maryland Native Plant Society Discussion Group, and Capital Naturalist. There are many others. In your Facebook account, find the Groups section and search for your topic of interest, whether it be houseplants, trees, flowers, or something else. There are groups for everyone and you can use them to crowdsource an answer or simply follow along and learn more about your subject of interest. Be sure to read and follow the rules of the groups you join.

Have fun, plant explorers!

By Christa K. Carignan, Coordinator, Digital Horticulture Education, University of Maryland Extension Home & Garden Information Center

Q&A: What is this white growth on my cherry laurel shrub?

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white prunicola scale on cherry laurel
An infestation of white prunicola scale on cherry laurel. Photo: University of Maryland Extension

Q: We have cherry laurel shrubs that were growing very well for a few years. Yesterday, I noticed some of the leaves on one side of a laurel were brown. When I looked closer, I found that all of the branches inside were covered with a white substance. What is it? What can I do about it?

Answer: The white substance on the branches is an infestation of white prunicola scale. Scales are very tiny insects that feed on plant sap. Their feeding leads to leaf yellowing, browning, and eventual dieback of branches.

Scale insects are challenging to manage. The waxy white substance they produce provides a form of protection from desiccation and predators. They produce three generations each year, so if a population is not controlled all at once, they can continue to reproduce and be a persistent problem.

When there is a heavy infestation of white prunicola scale and dieback is severe, it may be best to remove the shrub altogether rather than try to treat it. Depending on where the infestation is located, you may be able to prune out branches selectively and discard them.

Fertilized female scales overwinter on the bark of the branches, so another step in management is to apply a dormant rate of horticultural oil during the dormant season (when deciduous plants have lost their leaves). You can first use a soft-bristled brush to scrub off the scale patches gently. Then apply the horticultural oil.

white prunicola scale
White prunicola scale covering (female) and eggs. Photo: Brian Kunkel, University of Delaware, Bugwood.org

If female scales remain on the shrub, juveniles (called “crawlers”) will emerge in the spring. Crawler periods vary from year to year depending on temperatures. For this species, new generations may be out in May, mid-July to mid-August, and September.

The tiny juvenile crawlers are salmon-colored. You can place a simple trap to detect their activity; wrap a piece of double-sided tape around a few branches. When you see crawlers stuck to the tape, that is the ideal time to apply horticultural oil. Oil spray is the least harmful to beneficial insects such as ladybird beetles, which you want to keep in your landscape because they help tamp down on other pests.

White prunicola scale is a fairly common problem on cherry laurels. Residents who have these shrubs should check them periodically for leaf yellowing and white spots on lower branches. Scales are easier to manage if you catch them early.

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

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

What’s Eating My Rose Leaves?

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roseslug sawfly damage on rose
Rose slug 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 caterpillars. These are the juvenile stage of an insect called rose slug sawfly.

Rose slug 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 appearance. Some rose slug larvae chew through leaves entirely. Damaged foliage turns brown and curls up as the season progresses.

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

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

In Maryland, there are three species of rose slug sawflies that cause damage to roses: the bristly rose slug sawfly, the rose slug sawfly, and the curled rose sawfly. Most of the feeding activity on roses in Maryland is seen in May and June, but 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).

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

The best way to manage rose slug sawflies without chemicals is to monitor your plant(s) for damage symptoms and manually remove any larvae (squish them or toss them). Insecticidal soap, horticultural oil, and spinosad work well against these sawflies. These products are environmentally friendly insecticides listed by the Organic Materials Review Institute (OMRI). As with any pesticide, read and follow the label instructions carefully. Avoid sprays when your roses are in bloom, to protect pollinators and other beneficial insects.

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

Additional Resources

Rose Slugs on Shrubs | UME Home & Garden Information Center

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

Rose Insects & Related Pests | Clemson Cooperative Extension

Sawflies | University of Wisconsin-Madison

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

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

My Pachysandra is Dying, What Can I Plant in Its Place?

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landscape in partial shadeResident seeks groundcover options to replace Pachysandra. Photo: University of Maryland Extension / Ask an Expert

Q: My Pachysandra is Dying, What Can I Plant in Its Place?

A patch of Japanese Pachysandra in my yard was formerly healthy but in the past three years, it has died back. I would like to plant deer-resistant plants or groundcover in its place. Can you recommend some perennials I can try? This area gets filtered sun most of the day.

Answer: Volutella is a common fungal disease of Japanese Pachysandra that attacks both the leaves and stems and causes dieback symptoms. It is most severe in overgrown plantings and is often associated with scale (insect) infestations. This may have contributed to the decline of your plants.

It is a good idea to consider different options for this space. In addition to its susceptibility to Volutella dieback, Japanese Pachysandra has escaped garden cultivation and is now invasive in some natural areas of Maryland. We no longer recommend planting it. In the forest understory, it outcompetes native plants such as our spring ephemeral wildflowers and the wildlife (insects, birds) they support.

japanese pachysandra in a forested area
Invasive Pachysandra terminalis covers a large area of forested ground in Howard, County, Maryland. Photo: C. Carignan

There are other groundcover choices that are unique, beautiful, non-invasive, and adapted to Maryland’s growing conditions. For a partially shaded, moist area, try a combination of ferns – Christmas fern (Polystichum acrostichoides) and marginal woodfern (Dryopteris marginalis), sedges – blue wood sedges (Carex glaucodea or Carex laxiculmus) and Pennsylvania sedge (Carex pensylvanica), Canadian ginger (Asarum canadense), golden groundsel (Packera aurea), foam flower (Tiarella cordifolia), and creeping phlox (Phlox stolonifera). Some of these plants also support pollinators.

native plants garden
Groundcover plants were in bloom in April in the native plants garden at Camden Yards, Baltimore. From front to back: Phlox, Foamflower, Golden Groundsel. Photo: C. Carignan

Additional Resources

Planting Groundcovers | Home & Garden Information Center

Twelve Easy Native Plants for Shade | Montgomery County Department of Environmental Protection

Groundcovers | Plant NOVA Natives

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

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

Spotted Lanternfly Update: Be on the Lookout for Egg Masses

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spotted lanternfly adult and eggs
Adult Spotted Lanternfly and egg masses. Photo: Kenneth R. Law, USDA APHIS PPQ, Bugwood.org

Spotted Lanternfly (Lycorma delicatula) is a new invasive pest in the mid-Atlantic region. The first Spotted Lanternfly in Maryland was confirmed in Cecil County in October 2018. (See the Maryland Department of Agriculture press release.)

honeydew and sooty mold
Honeydew and sooty mold from Spotted Lanternfly feeding. Photo: Kenneth R. Law, USDA APHIS PPQ, Bugwood.org

This insect is known to feed on 70 species of plants including forest and agricultural crops such as grapes, hops, apples, peaches, figs, oaks, maples, black walnuts, and tree of heaven. Spotted Lanternflies feed on plant sap and secrete a sticky substance called honeydew. Black sooty mold grows on the honeydew and blocks sunlight from reaching leaves, impairing photosynthesis. Plants may become weakened and more susceptible to secondary invaders such as ambrosia beetles. The long-term effect on the health of trees and vines is unknown at this time. Continue reading →