Q: I think I might have giant hogweed on my property, or maybe it is poison hemlock. How can I tell for sure?
A: Giant hogweed (Heracleummantegazzianum) was found recently in Clarke County, Virginia, and it has raised awareness and concern about the plant – and rightfully so. The plant produces toxic sap that can cause very severe skin inflammation. We have received a lot of questions about it lately.
Poison hemlock Photo: E. Nibali
What you have here is NOT giant hogweed. It is poison hemlock(Coniummaculatum), which is much more common. The ferny foliage makes it possible to distinguish it from giant hogweed.
Ground ivy or creeping Charlie (Glechoma hederacea). Photo by Betty Marose
The famous quotation about the certainties of life which we all know includes death and taxes should also mention weeds! They are sprouting up all over. Even the most meticulously tended landscapes are not immune.
Where to Begin?
The first step is identification. You need to know your opponent. Control is more attainable if you know whether it is a grassy or broadleaf weed. Is it an annual, perennial or biennial? When does it germinate? Fall, spring, or summer?
Bamboo. Photo: Chuck Bargeron, University of Georgia, Bugwood.org
Maryland property owners are limited to self-help when dealing with plants encroaching on their properties. This is not legal advice.
Have a neighbor who has planted bamboo or another invasive plant species near your shared property line and now that plant has started encroaching on your property? What can you do in this situation? Maryland has only one decision discussing damage from plants growing on a neighbor’s property. In Melnick v. C.S.X. Corp., the Court of Appeals of Maryland limited landowners to self-help to remove invasive plant species from growing on your property. The courts in Maryland have found that “it is undesirable to categorize living trees, plants, roots, or vines as a “nuisance” to be abated. Consequently, we decline to impose liability upon an adjoining landowner for the “natural processes and cycles” of trees, plants, roots, and vines.” (Melnick, 520-521). Self-help means it will be up to you to remove the roots, limbs, vines, and other plant debris and not the neighbor who planted the invasive plant species. A neighbor cannot seek damages in court for the damages caused by the invasive plant species.
Have you experienced one or more of these garden scenarios?
It’s early April and chickweed, henbit and other winter annual weeds are growing so thickly in a vegetable or flower bed that the soil can’t be seen.
The winter rye cover crop you mowed last week is growing back.
You tilled and raked a bed that you couldn’t plant right away and now weeds are coming up everywhere.
The rainy summer weather is favoring weeds over crops so that the weeds are taking over walkways and dominating beds that you want to plant with fall crops.
Neighboring plots in your community garden have been abandoned and weeds are growing wild and reproducing!
I can’t bear to look… I’m going back inside
This stirrup hoe is great at removing large weeds, but brings lots of weed seeds up to the top two inches of soil where they have a good chance of germinating.
Un-controlled weeds compete with garden plants for water and nutrients, are hosts for insect pests and diseases, and can demoralize the toughest gardeners. Tilling, pulling, chopping, and hoeing are all fine weed control techniques under the right conditions, but they also disturb soil allowing even more weed seeds to germinate and flourish.
There’s another way: occultation. The common dictionary definition is “an event that occurs when one object is hidden by another object that passes between it and the observer.” For gardeners and farmers, it’s covering the soil to create a dark, warm, moist environment. In 2-4 weeks, this no-till technique can:
smother and kill young weeds
smother larger weeds and grasses
accelerate the decomposition of mowed cover crops and weeds
promote the germination of weed seeds and then smother the seedlings
Weed barrier pinned down over a bed filled with winter annual weeds. It was ready to plant in two weeks. Tough perennial broad-leaf weeds and grasses may be weakened but not killed.
With spring gardening season right around the corner, lawn questions have been rolling into the Home & Garden Information Center (HGIC). Here I’ll address some of the most common questions about weeds and overseeding.
Dealing with Winter Weeds
Chickweed
In late winter/early spring, we typically see winter annual weeds in thin, under-fertilized, wet, or shady areas. These weeds germinated in the fall and will die as the weather warms up later in the spring. In my observations, this has not been a particularly bad year for winter annuals. They are favored by wet, mild winters and I think we had just enough “bitter cold” in January and a fairly dry stretch through December and January to reduce populations.
Typical winter annual weeds include chickweed, henbit, purple deadnettle, and shepherd’s purse. Options to address these winter annual weeds include hand pulling, spot spraying with a broadleaf herbicide, or waiting until they die once weather climbs to the 60’s and 70’s on a regular basis. For perennial weeds like dandelion which will start to re-emerge later this month, hand-pulling or spot spraying are the best methods for control.
Warm early October weather has extended the “overseeding window” for fall lawn care. While the first week in October is usually the traditional cutoff for establishing new lawns or rejuvenating existing lawns, the warm early October weather has extended the window by 1-2 weeks.
You can read my September blog post for more information on overseeding and you can still do it, but this follow-up post will deal more with a question that has been coming into the Home & Garden Information Center as of late: “I established a new lawn (or overseeded) in September and some weeds are starting to come up — now what?” Continue reading →
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.
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.
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.
With spring gardening season right around the corner, lawn questions have been rolling into the 
