Q: I have a plant coming up in and around a bed of early bulbs. The leaves are triangular and oppositely arranged on square stems. I think it’s a lamium ground cover (like ‘White Nancy’), but I don’t remember planting it there. I’ve sent along a photo to help with the ID.
A: Unfortunately, it looks like purple deadnettle has moved into your landscape bed. Purple deadnettle is a common weed of sunny, fertile sites. Seeds germinate in cool winter soils, and plants grow quickly in early spring. Flowers are produced along the stem, with seeds shedding in spring. Plants then die back, and return from seed the following winter. Like other members of the mint family, purple deadnettle has square stems.
In spring, some farm fields are completely covered with a purple hue from this plant’s purple leaves and flowers. Purple deadnettle can be managed by pulling plants before they flower, mulching soil surfaces to cover seeds, or by applying a pre-emergent herbicide in autumn if the infestation is severe.
Q: Underneath my magnolia tree, I have a plant popping up with dark green, very tough stems. There are no obvious leaves, but the stems bend easily and are mostly hollow. A neighbor called it scouring rush.
A: Scouring rush or horsetail is a survivor from prehistoric times and was traditionally used as a pot scrubber, hence one of its common names. The brittle, hollow stems contain silica, making the plant useful in olden days for cleaning.
Two types of horsetail grow in our area; both are aggressive perennial weeds. One type has tall straw-like stalks, while the other grows with short whorls of light green stems. Both are highly aggressive in the garden, and will take over entire beds through deep rhizomes that can grow 20 feet deep and spread 300 feet horizontally.
Even planting these plants in pots is risky because they are so difficult to kill once they inevitably escape. These plants are even resistant to many herbicides available to homeowners, so a professional may be needed to control this weed. The plant is toxic to horses.
Q: Carpenter bees have become a problem around my front porch. They seem to return to the same place each year. I can see the perfectly round holes they produce, then later I start to see sawdust on the ground. They seem very aggressive and bother my grandchildren, although no one has been stung.
A: Carpenter bees are important pollinators, but they can also cause significant damage by tunneling nests into structural wood. Female carpenter bees use their strong jaws to chew galleries in wood. Males defend the territory around the nest, buzzing and dive-bombing passersby. Males are harmless, however, because they don’t have stingers. Females are reclusive, and are reported to sting only when handled.
Juvenile carpenter bees develop inside wood galleries, emerging as adults in August. These adults overwinter inside the galleries, emerging in spring to mate. Females prefer to return to the same nesting sites from year to year, a habit that can result in significant structural damage over time. To manage carpenter bees, apply a labeled insecticide dust to the gallery opening in early spring or summer, when nesting is apparent. Wait several days, then seal each gallery with caulk, wood putty or sealant. Significant infestations may take several years to control.
Q: I have a large blue spruce that has an obvious infestation of bagworm. The first year I noticed a few brown bags in winter near the top of the tree, but now I see quite a few bags along one side. I want to control them, but I worry about spraying anything in my yard since I keep bees.
A: Evidence of a bagworm infestation is most easily seen on plants in late winter, before new leaves have emerged. The brown, cone-like bags can be found hanging from the twigs and branches of many conifers as well as deciduous trees. Eggs hatch around the time of the first bloom of tree lilac, with 500 to 1,000 juvenile caterpillars emerging from each bag. The young caterpillars spin a silken thread and are carried by the wind to new branches or other plants. Larvae eat plant leaves, using the leaves to build bags around themselves. They are well camouflaged by this plant tissue for most of the growing season.
Deciduous plants (honey locust or sycamore, for example) can withstand bagworm damage, and control is usually not necessary. On evergreens, bagworms can cause significant damage, and can kill plants over several years. Insecticidal soap, horticultural oils or Bt for caterpillars can be used to control young larvae. These products are safe to use around bees, and don’t leave a residue toxic to bees visiting later. Bt for caterpillars has no effect on bees.
The challenge will be applying these products to a large tree; a professional applicator will likely need to do the work, and repeat applications may be necessary. Keep in mind that spruce and other conifers won’t produce new leaves on branches defoliated by bagworms. Oftentimes gardeners decide to take down infested trees because the ornamental value has been lost.
Denise Ellsworth directs the honeybee and native pollinator education program for the Ohio State University. If you have questions about caring for your garden, contact her at 330-263-3700 or click on the Ask Denise link on her blog at www.osugarden.com.