Author:Miri

Q&A: How to Manage Japanese Beetles

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an adult Japanese beetle on raspberry fruits
Adult Japanese beetle on a ripening raspberry cluster. Photo: Miri Talabac, University of Maryland Extension

Q:  Japanese beetles have been ravaging my yard for a few summers now. I heard Milky Spore can be a natural way to treat them. Is that right?

A:  Japanese beetle grubs feed underground on plant roots (often in lawns), and the adults feed on foliage and flower petals on perennials, shrubs, and trees. It’s possible only one of those two life stages will pose a problem for a gardener while the other does not, so you won’t necessarily have to tackle both. In fact, a lot of lawn grub treatments are unnecessary, because any grubs encountered are not abundant enough to create noticeable lawn damage, or someone mistakenly blamed grubs for turf dieback caused by other factors. 

Milky Spore, the product name for a biological control agent for Japanese beetle grubs, is a naturally-occurring bacteria that infects the grubs and kills them. Unfortunately, University field trials have found it is not reliably effective. Microbial levels might require several years of build-up from annual applications of the product to reach populations sufficient to reduce grub numbers, which can be costly.

You do have other options; the adults of this species won’t be out for a month or so yet. Beneficial nematodes can be applied to a lawn where white grubs feed, which will parasitize them and kill them. Weather conditions need to be just right during application because they are very perishable, but once nematodes get settled in, they appear to be a more promising solution.

Lower-toxicity insecticides can be used as a last resort, though check with local government rules about applications to turf since some areas restrict pesticide use on home lawns. It may be best (or necessary, for certain ingredients) to hire a certified pesticide applicator to make such treatments.

Residents who have a lawn dominated by tall fescue will rarely have any serious Japanese beetle grub issues, because this is not the turf type they prefer. (Kentucky bluegrass, fine fescue, and perennial ryegrass are those at risk.)

Adult beetles are simpler to deal with. Simply hand-picking them off of shrubs is an immediately effective tactic. Knock them into a container of soapy water to kill them, since they drop readily when disturbed. These beetles like to congregate, so removing them in the morning, before they can produce a waft of aggregation pheromone to attract others to the banquet, means that you can easily reduce the plant’s risk of damage.

It’s not necessary to nab every last beetle or prevent all chewing damage. Birds, lizards, predatory insects, and other natural helpers will help keep populations suppressed as well.

Although hanging trap bags use a pheromone lure, they attract more beetles than they capture, and the incoming beetles might still eat plants before heading to their doom, so you might as well skip that approach and just intervene by hand.

Don’t worry too much if damage sneaks up on you: even heavily-chewed shrubs may surprise you by rebounding well on their own, once the adult beetle activity has ended later in the summer. More information about their life cycle and management options can be found on our White Grub Management on Lawns and Japanese Beetles on Trees, Shrubs, and Flowers pages.

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.

Q&A: What Screening Plants Fit in a Small Space?

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a row of small evergreen arborvitae shrubs near a brick building
‘Emerald Green’ Arborvitae screening a property line. Photo: Miri Talabac, University of Maryland Extension


Q:  I have limited space in a tiny city front yard and would like to block some of my view of the street. What types of evergreens would work well but not get too wide?

A:  The width of the mature plants is the tricky part, since many upright evergreens mature at least 3 to 5 feet wide at their base, and not many are trimmable to keep them smaller. Plant options will depend on whether you have full sun or some shade from nearby trees or the house itself. Few city yards have issues with deer (though some do), so I’ll assume for now that browsing is not a factor.

Soil compaction is a common challenge, and poor drainage (is a roof downspout nearby?) can exacerbate root stress and cause plants to fail. If the site drains reasonably well and receives full sun in summer, your choices include slender-growing cultivars of widely-used evergreens. (Alas, there are very few native options to fit these criteria.) Examples include arborvitae (Thuja), juniper (Juniperus), yew (Taxus), Japanese plum yew (Cephalotaxus), boxwood (Buxus), and holly (Ilex).

Yew as well as broadleaf evergreens like the boxwood and holly can be pruned relatively easily to manage size, since they rebound well. Even so, it’s best to select cultivars that will mature close to the size you can accommodate without having to prune, both to save yourself the task and to reduce plant stress.

For the rest of those listed plants, especially other conifers (needled evergreens), pay close attention to expected mature size on the plant tag and make sure you have room, taking into account overhead utility lines. Take that stated size with a grain of salt too, since older plants keep growing and will not plateau at a set height forever.

Yew, Japanese plum yew, boxwood, and holly will handle a fair amount of shade and still look good, though the less sun they get, the less dense they might stay (or growth will slow). None of these species are super fast-growing (otherwise they’d get much too large for the space), but boxwoods and the upright yew varieties are among the slowest in pace. Even so, planting small, young specimens will be easier on both you and the plants (especially if shade tree roots are infiltrating the area), and they will catch up.

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.

Q&A: Can a Tie Stuck in a Tree Be Removed?

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Plastic tree tie embedded in a crapemyrtle trunk because it was not removed promptly. Photo: Miri Talabac, University of Maryland Extension

Q:  There’s a crapemyrtle in our new yard that has a plastic cable tying it to a stake that has become stuck in the wood. Should I cut it out so the trunk can heal?

A:  No, that will cause more damage and potentially lead to even more wood decay and crown dieback. All you can do is carefully cut off the excess outside the bark (don’t worry about making it flush; you don’t want to cut into live wood). Gardeners and landscapers should monitor any trees they stake for indications a trunk tie is abrading, cutting into, or being enveloped by the bark. Most trees don’t need staking, and even when they benefit from it, removal of the stakes and ties is recommended after six to twelve months of use. No tie or trunk brace should be so tight that the trunk cannot sway a bit in the wind.

It’s hard to predict how much of an impact the damage you found will have on the branches that particular trunk feeds. Fortunately, the tie in your case did not encircle the trunk, just brace one side of it; I’ve seen several instances where encircling ties become embedded and essentially strangle and kill the entire top of the tree (Leyland cypress and Arborvitae being common victims).

Tree and shrub wood expands outwards as it grows, increasing in diameter as each ring of new wood growth is formed yearly. Although an imperfect comparison, there are parallels to how coral reef colonies grow – over time, the innermost “skeleton” is no longer alive, though it provides support, and the outer shell of tissues is living and actively growing, save for the bark itself. (You can think of bark a bit like nails on a person or pet…it’s produced by live tissue, but the material itself is not alive.)

If the tie extensively obstructs the cambium that lies under the bark (the live tissues moving water, sugars, and nutrients around the tree), one or more major branches above it may die back in the coming years, for which there is no treatment. In some cases, the obstruction just becomes buried under years of growth, hiding it from view. (This is a hazardous situation if the tie or obstructing material were metal, and the tree was removed and chipped up one day.)

Trees can’t heal quite the way animals do, but with luck, this damage will remain minor and not cause significant dieback. If it does, though, you’ll have to cut down that trunk. Since crapemyrtle tends to sucker readily, new growth can take its place if you let a sucker mature into another trunk.

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.

Q&A: What Causes Aloe Leaves to Turn Yellow?

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potted aloe vera plant
Aloe vera plants.

Q:  I have an aloe indoors that is developing some yellow leaves. Do I need to feed it or change something else about how I take care of it?

A:  Leaf yellowing is a difficult symptom to trace back to a particular issue since in general it can be caused by overwatering, under-watering, under-fertilization, too little light, too much light, pest feeding, and a few other factors. With indoor succulents, too much light is a rare problem, and accidental over-watering is relatively common, which is why I presume low light and soil moisture are the conditions needing evaluation first.

A leaf that turns yellow is one a plant is probably about to shed, so even if the original issue is resolved, be aware that it won’t usually green up again. That’s okay, as long as the shedding isn’t excessive (and if it is, it might be too late to fix); plants can reabsorb some of the resources stored in the leaf before it dies and falls. It’s also perfectly normal for any plant to shed its oldest leaves from time to time since they have limited usefulness to the plant as they age or succumb to cumulative injuries or stresses.

Succulents like aloe thrive in bright light while indoors, so it’s possible yellowing has begun because the plant is running low on stored energy that has allowed it to tolerate insufficient light so far. (Plants make their food from light, so while occasional fertilization can supplement their nutrition, it’s not a substitute for receiving enough light.) While indoors, aloe grows best where it gets either several hours of direct sunlight close to a window or is placed under plant grow lights that can supplement or replace natural light (if window light is insufficient).

Succulent roots should get fairly dry between waterings, though each watering still needs to be thorough so all of the potting mix is well-moistened each time to eliminate dry pockets. Extra water should freely drip out of the bottom drain holes of the pot. Feel the soil about an inch deep (or more, depending on pot size) and only water when it’s become pretty dry to the touch at that depth. Be sure to empty any drained water in a saucer promptly so the pot doesn’t sit in water, as this can kill roots. Root rot can result in leaf yellowing because there are not enough healthy roots left to support all of the plant’s foliage. As with other triggers for shedding, the oldest, lower leaves are usually sacrificed first.

If you haven’t fertilized the plant in several months, it might benefit from a light dose. Normally indoor plants don’t need fertilization during the fall through winter, but if a plant has been nutrient-deprived for a while, it may benefit from replenishing those nutrients in the soil. The precise fertilizer formulation doesn’t matter much in this case, though nitrogen is likely the nutrient of greatest importance (the N in N-P-K ratios) for overall plant health and leaf color, so it can be chosen as the highest number of the three (such as 3-1-2 or 10-5-5 as arbitrary examples). Regardless of the type of fertilizer chosen, follow package instructions about how to dose it. You’d probably only need one dose (maybe at most two) to last the plant through the winter since it won’t exhaust those nutrients quickly. If you suspect scale, mealybugs, thrips, or mites are causing damage, get them under control first, since you don’t want to feed the pests extra nutrients with the fertilization.

Indoor plants grow slowly (if at all) in winter, and succulents tend to be slow growers in general, so it may take some time for the aloe to show any improvement, which is fine as long as it isn’t declining further in the meantime.

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.

Q&A: How Can I Get Wasps Out of My Compost?

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Yellowjacket (Vespula sp.). Photo: M. Talabac

Q:  Wasps took up residence in my compost pile this year. I could avoid them for a while, but I’m hoping I can use the pile again next spring. How can I get them out of there?

A:  Ground-nesting yellowjackets are probably the culprit here, and the good news is that they will disappear on their own by winter. In our area, social wasps like hornets, yellowjackets, and paper wasps don’t reuse the same nest for more than one year. By late autumn or early winter, the old queen, workers, males, and any juveniles that did not have time to mature will all die. Only mated young queens survive, leaving the nest of their birth to disperse and overwinter in a sheltered spot by themselves. They seek out insulated spots like hollows under fallen logs and nooks in stone walls, go into the insect version of hibernation, and emerge in spring as it warms up, each flying off to find her own site to start a new nest. She does all the nest-building and larvae-feeding work by herself until the first generation of young matures, so she has a limited ability to defend it from disturbance.

Nest remnants left in the compost pile will be abandoned (or will at least contain dead wasps) during winter, when you can safely dig it out for removal or just leave it to compost with the rest of the pile contents. Wild animals can also tear apart abandoned wasp nests, looking for easy-access morsels to snack on, though this presumably happens more regularly with visible above-ground nests.

Preventing a new generation of wasps from choosing the same appealing nest site in a future year might be challenging unless you enclose the pile in insect mesh or something to discourage queen wasps from exploring it in spring. Regular turning of the pile – recommended to keep it well-oxygenated anyway – might disturb a new queen too much to allow her to successfully begin a new nest.

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.

Q&A: Where Can I Squeeze In Spring Bulbs?

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Glory-of-the-Snow bulbs flowering in a lawn in late March. Photo: M. Talabac

Q:  I want to add spring bulbs to my garden but have limited space given how many mature perennials and shrubs are already growing there. Can I squeeze them in somewhere else?

A:  Autumn is bulb-planting season for all of those spring-flowering jewels like tulip, daffodil, crocus, aconite, hyacinth, and snowdrops, and fortunately they don’t take up nearly as much space as your typical perennial in terms of the planting site. I would not dig into the root system of an established perennial or shrub – too risky for causing damage that might result in dieback or reduced overwintering success – but you can certainly fit them into spaces between. You probably don’t want too many under the canopy of a shrub. Depending on how early it leafs out, the shrub could block needed sun and rainwater from reaching the bulbs below, but around its perimeter should be fine.

Good companions for early-flowering bulbs are late-sprouting perennials, so that by the time the bulbs are looking ragged and losing foliage for summer dormancy, the perennial is hiding it with fresh foliage.

One creative option is to scatter some of the minor bulbs in your lawn, if you won’t be walking on that area too often and compacting soil or crushing foliage, and if you don’t need to start mowing soon after blooms begin. Candidates include Crocus, Glory-of-the-Snow (Chionodoxa), Siberian Squill (Scilla siberica), Winter Aconite (Eranthis), Reticulated Iris (Iris reticulata), and Snowdrops (Galanthus). Be advised, though, that a few of these species might be prone to naturalizing outside of your lawn, so use caution around woodlands and parks.

Native alternatives with bulb-like underground structures include Spring Beauty (Claytonia), Squirrel-corn (Dicentra canadensis), and Dutchman’s-Breeches (Dicentra cucullaria), though the Claytonia is the only one that may stay short enough to be mown-over high and whose foliage blends-in well with the grass. Many of our native ephemeral wildflowers – early-season bloomers that go fully dormant come summer – are unfortunately harder to find for purchase.

Growing bulbs in containers would be your other option, but this can impact winter hardiness since the bulb’s root system is fully above-ground, not benefitting from the insulation of being planted in the earth. Potting mix also dries out faster than in-ground soil, so it might be challenging to make sure dormant bulbs in pots don’t get too dry while also not accidentally over-watering them. If the container is large enough, you can layer two or three tiers of bulbs at different depths so they bloom in succession, or use bulbs planted below annuals or shallow-rooted perennials to provide summer color. Bulbs are planted at different depths depending on the species, though, so take note of planting instructions when you select which to purchase and decide where to plant.

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.

Q&A: Late Bloomers for the Garden

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a red-spotted purple butterfly is feeding on nectar from a native Eupatorium plant with white flowers
Red-Spotted Purple butterfly on a native Eupatorium in September. Photo: M. Talabac

Q:  A lot of my new native plant garden beds contain species that bloom in spring and early/mid-summer. What can I add for pollinators that blooms late?

A:  Fortunately, there are numerous late-season nectar sources, though most are sun-loving species. They are very attractive to migrating Monarchs and any other butterfly on the wing in late summer and autumn, plus bees, wasps, beetles, flies, and plenty of other insects. Seed-eating birds also appreciate the food source once the seeds of those plants ripen by the end of the growing season; nature’s bird feeders.

Lots of late-flowering native plants are in the aster family, including: Ironweed (Vernonia); Goldenrods (Solidago and Euthamia); Asters (formerly genus Aster, now named Doellingeria, Eurybia, Ionactis, or Symphyotrichum); Cut-leaved Coneflower (Rudbeckia laciniata); Blazing-star (Liatris); Elephant’s-foot (Elephantopus); Beggarticks (Bidens); Wingstem (Verbesina); Helen’s Flower (Helenium); perennial Sunflowers (Helianthus); Climbing Hempvine (Mikania scandens); and the Eupatorium group (several common names and genera; Eupatorium, Eutrochium, Conoclinium, Ageratina).

Outside of the aster family, you can also consider Rosemallow (Hibiscus), Obedient Plant (Physostegia virginiana), Turtlehead (Chelone), Common Witchhazel (Hamamelis virginiana), Gentian (Gentiana), Tall Phlox (Phlox paniculata), Lobelia (Lobelia), and Flowering Spurge (Euphorbia corollata).

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.