September is synonymous with school. So, this week we are
getting back to basics with a post that defines foundational gardening terms.
The better you understand these terms and phrases, the easier it will be to
identify, select and care for plants in your landscape.
Growing season: The period between the beginning of growth in
the spring and the cessation of growth in the fall.
Hardiness zone: Expressed as a number and letter combination
from 1a to 13b, the US Department of Agriculture has assigned a zone to every geographic
area of the United States based on the average annual minimum winter
temperature. Tags on plants sold commercially often identify the zone(s) in
which the plant will grow.
affected by landscape, structures, or other unique factors in a particular
for the three major plant nutrients contained in manure, compost, and
fertilizers. N stands for nitrogen, P for phosphorus, and K for potassium.
started from seed that grow, mature, flower, produce seed, and die in the same
Biennial: Plants that take two years, or a part of two years, to complete their life cycle. By freely reseeding, a biennial plant may seem to come back year after year, but you are actually seeing new plants.
Perennial: A plant that lives more than two years and produces new foliage, flowers, and seeds each growing season. Tenderperennial: A perennial that is not tolerant of frost and cold temperatures. Applying a winter mulch can help it survive It may die off above ground and regrow from the roots.
Woody perennial: A plant that goes dormant in winter and begins growth in spring from above-ground stems. Herbaceousperennial: A plant that dies back in the winter and regrows from the crown in spring.
Exotic: A plant of foreign origin or character; not native; introduced from abroad, but not fully naturalized. Naturalize: The process whereby plants spread and fill in naturally.
Native plant: A plant indigenous to a specific habitat or area. Nativar: A plant that is a cultivar of a native plant. Cultivar: A cultivated variety of a species. Propagation of cultivars results in little or no genetic change in the offspring, which preserves desirable characteristics.
Integrated pest management.
A method of managing pests that combines cultural, biological, mechanical, and
chemical controls, while taking into account the impact of control methods on
Invasive. Growing vigorously and outcompeting other plants in the same area; difficult to control.
Noxious weed. Weeds that have been declared by law to be a species having the potential to cause injury to public health, crops, livestock, land, or other property. Noxious weeds are very invasive. There are 124 plants in NC that meet the legal criteria.
When a gardening term has you stumped, refer to the glossary chapter of the Master Gardeners Handbook for a definition – there are hundreds of entries — and a small dose of continuing education.
Typically I don’t get riled
up about weeds that are easy to pull up by hand, but Japanese stiltgrass (Microstegium vimineum) is a HUGE
exception. Despite its fibrous, shallow root system, in just three to five
years this invasive species can overtake a natural area, pushing out natives
and non-natives alike. It is also detrimental to ground-nesting birds and can
contribute to fueling forest fires. I’ve observed more and more of it in local
forests and parks where I hike as well as the roadsides in my woodsy Durham County
neighborhood. It’s a sad sight, especially on conservation lands.
This spring was the first time I noticed stiltgrass at a friend’s home in the Piedmont region of Virginia. Normally when I‘m there I’m grousing about periwinkle (Vinca minor) and winged burning bush (Euonymous alata), two other invasive species which I have previously blogged about. I admit to feeling a bit of poetic justice at the sight of the one invasive (periwinkle) being overtaken by another (stiltgrass). But the feeling was fleeting. Every subsequent feeling has been more along battle lines – how can I fight this?
Before attempting to eradicate any weed, you want to be sure you have identified it correctly. When I first noticed stiltgrass, its structure and wispiness reminded me of bamboo, albeit a tiny version.
In plant ID lingo stiltgrass is a “prostrate to erect, sprawling and freely branched summer annual with spreading stems that root at the nodes … Leaves are rolled in the bud; ligules are short membranous with hairs …”1 If you’re thinking, hey what IS a ligule? Don’t despair! Stiltgrass does have one distinguishing characteristic that you need not be a botanist to recognize: Each leaf on stiltgrass has a silvery midvein that divides the leaf unevenly.
Note in the accompanying photo gallery how this feature is absent from other plants (some weedy, some not) that are often mistaken for stiltgrass.
The root structure of stiltgrass is also distinct from other weeds often mistaken for stiltgrass as noted in these photos. (Stiltgrass is the photo with the brown background.)
Growth habit and lifecycle Japanese stiltgrass seeds germinate in early spring. The plants grow and strengthen through the summer. In June the Virginia patch was about six inches high; At the beginning of August, the plants were two to three feet tall. In NC it flowers from mid-September through October and soon after flowering the seeds are dispersed – 1000 seeds per one wispy plant! Seeds stay viable in the soil for four years.
I consulted a lot of sources before writing this post and it seems that there is not one “right place” for stiltgrass to thrive. Some sources advised sun, others shade. Some moist woodland, others dry roadsides. Apparently, it is adaptable to a variety of conditions. It will even tolerate a mild frost. And, it really makes its presence known in areas where the soil has been disturbed. This may have been a factor for the Virginia property I referred to earlier as several very large trees were felled, cut up, and carted away from the land over the last year. That kind of activity definitely disturbs soil and surrounding environment.
Understanding the lifecycle of a weed or any unwanted plant is important because in order to stop it from spreading you need to stop it before it seeds. The flowerhead on stiltgrass though is quite small as are the seeds, so best to act based on the time of year than on a visual. From now through September is a good time for those of us in Durham County to act.
Tactical solutions Here are three ways to combat a stiltgrass invasion. Which tactic you choose will depend upon how much stiltgrass you have, where it is growing, and your comfort level with chemicals.
Hand-pulling or digging While this tactic is typically my go-to for weeding, it only makes sense with small infestations and even then, there are some caveats. When we pull weeds by hand, we disturb the soil which is often enough to bring previously dormant seeds to the surface where they will receive the sunlight they need to germinate. “Hand-pulling of stiltgrass plants needs to be repeated and continued for many seasons until the seed bank is exhausted.“2
Mowing If stiltgrass is growing in your lawn (or what passes as your lawn) then mowing seems like an obvious tactic. But when stiltgrass is mowed too early in its lifecycle, the roots re-energize and send new shoots above ground more quickly than the first time and it may flower and seed earlier, too.3 If possible, delay mowing stiltgrass until the end of August to deter regrowth or seeding.
The best way to prevent stiltgrass in a lawn is to follow best practices for lawn seeding and care. To learn how to properly maintain your lawn consult Carolina Lawns: A Guide to Maintaining Quality Turf in the Landscape
Herbicide My friend has given me complete freedom to attack the burning bush and the stiltgrass around his home, but not the periwinkle which he likes very much. After three decades it is as much a part of his mountain retreat as the cabin it surrounds. Knowing I needed to save the periwinkle, I turned to the one-percent solution. This is a tip I received from a weed control expert at a local botanical garden during an educational class. (We master gardeners need to complete at least eight hours of education each year.) Extension programs also endorse this solution.
A half to one-percent solution of glyphosate will kill Japanese stiltgrass without harming the other plants around it. Ready to spray containers of glyphosate I have purchased held an 8% solution. Concentrated varieties were 18%. I share this information to drive home the point that more IS NOT better. I suited up (long pants, long-sleeved shirt, tall rubber boots, nitrile gloves) before mixing up a much diluted version of the herbicide and I sprayed the stiltgrass.
Do not use glyphosate on your lawn. Pre-emergent herbicides for crabgrass are recommended for preventing stiltgrass from growing in a lawn. These are best applied in late spring or early summer so that the lawn has time to recover.
Weeding is a commitment Whichever method you choose, plan on at least a five-year commitment. Since I don’t live on or near the property I treated, I won’t know the outcome of my effort until the fall. But I already understand that my work is not finished. I was working in a natural area on a mountain side. I could not reach all the stiltgrass. Hopefully, the patch of stiltgrass growing on your land is smaller, more easily accessible and responds to your chosen method of treatment.
Weeds, I once thought, are a curse. Perhaps the Lord,
looking down on Carolina and musing that it was just too nice, sent Gabriel to
bring us extra hot weather and especially bountiful crops of weeds.
I still think weeds are a curse but have found with them, now and then, a
Time is important. Before I retired I weeded when I could,
but I was often away and, by mid-July, had surrendered my yard and gardens and,
when I passed by them, looked the other way. Now I have time to keep after
weeds and have discovered a sort of tipping point: After several years of faithful but not
obsessive weeding, I now hold the weeds at bay and mid-summer no longer looks
During weeding, one can pass into an agreeable meditative state or one can wear a portable radio and multitask. One can relax. A serious mistake is unlikely unless you are weeding someone else’s yard and, anyway, nature is so forgiving.
I don’t eschew herbicides; but use them sparingly – on that dratted Bermuda grass, say. Some weeds, especially after rain, come out, root and all, rather easily; crabgrass, the promiscuous Japanese stilt grass, and henbit for example. And getting down close to the ground to weed shows us so much more; the weeds themselves and their habits, occasional interesting bugs (very useful if we discover a trail of ants about to foray into our house). Early this spring, during weeding, I found myriads of beautiful red and black box-elder bugs under our maples. Sometimes, joy of joys, we may encounter a really good bug, perhaps a praying mantis.
Let’s give weeds their due – remarkable, aren’t they? Looking over a bed that seemed, at first, weed free, I spot a weed and, pulling it up, spot another close by. Soon, a forest of weeds has appeared where none seemed to be just a minute before. And how do they spring up so promptly after a rain? Coexistence isn’t an option – weeds, like Japanese beetles, don’t know about sharing.
In life we seek positive results. And so it is with weeding: What is more positive than standing up from a pile of rooted-up weeds and admiring an immaculate garden bed? Even better, sometimes one can put that pile into the compost bin and turn it into useful stuff.2 If only the rest of life were like that.
Photo captions, clockwise from upper left: Box-elder bug (credit: Whitney Cranshaw, Colorado State University, Bugwood.org), henbit, Japanese stiltgrass, Bermuda grass.
1 Lucifer may have participated. If lawns are in hell, they are planted in Bermuda grass. And a close reading of Job would surely turn up a reference to Bermuda grass.
Last year, I noticed a spreading wildflower around the base of my beautyberry bushes (Callicarpa Americana) in a perennial bed along the south side of my house that I originally thought was Wild Strawberry1 (Fragaria virginiana). It appeared amongst my creeping Jenny (Lysimachianummularia ‘Aurea’), which I was using as a ground cover.
This year, it has taken over the bed and migrated into the lawn and even the aggressive creeping Jenny has lost its battle with this plant, which now covers every plant in the bed that isn’t higher than five inches. A lesson that I should have learned a long time ago … if the gardener ignores a few weeds in the garden, the gardener risks bigger issues in the future. The culprit, as it turns out, is a perennial weed commonly called Mock or Indian Strawberry (Duchesnea indica)2,3and not the native wildflower, Wild Strawberry4. The relatively sudden appearance of this plant in my yard is likely the result of birds eating drupes elsewhere and spreading them to my yard2.
Mock Strawberry (Duchesnea indica)
Mock strawberry is an herbaceous perennial plant of a height between three and eight inches and spreads by runners or hairy stolons3, 5 into large colonies of plants over time. Each plant consists of small trifoliate basal leaves with long petioles that develop from a root crown2. Each leaflet is about one inch across and elliptical with rounded toothed lobes5. Its five-petal yellow flowers of about 0.5-inch diameter appear in spring and develop into tiny edible red tasteless fruit or drupes that are held upright2. Small red seeds form on the bumpy surface of the fruit. It prefers moist soils and partial sunlight and can adapt to regular mowing because of its low growing habit2. It was introduced as an ornamental plant from south Asia.
To help reduce Mock Strawberry lawn encroachment, it is recommended that one improve surface drainage, aerate when needed and conduct infrequent watering5. If the gardener is interested in chemical control, the recommendation for both pre-emergence and postemergence control formulation is provided in detail on the NC State TurfFiles website5. In my perennial bed I have decided to control it by hand weeding and mulch.
Comparison to Wild Strawberry
Wild Strawberry or Scarlet Strawberry can make a desirable ground cover in woodland gardens with some wildlife value1, 4 and it can control erosion on slopes. Mock Strawberry is easily distinguishable from the native Wild Strawberry because its flower is yellow and the Wild Strawberry has a white flower. Other differences include lower growing and smaller leaves of the Mock Strawberry and the drupes are erect. The Wild Strawberry drupes tend to hang downward and the teeth on the leaf edges are sharp-pointed rather than rounded. Best of all, the fruit of the Wild Strawberry is juicy and with a pleasant sweet-tart taste whereas the Mock Strawberry is bland with a dry texture.
Your yard may not have ideal conditions for Wild Strawberry as a ground cover but nevertheless cultural control of Mock Strawberry is more desirable than letting it takeover your ornamental beds and crowding out more desirable lower growing plants.
After several years of trying to stay ahead of the weeds in my landscaped beds, I am coming around to an option I had not seriously considered before: planting ground covers as weed control.
A variety of annual and perennial broadleaf weeds consider my yard home year round. Most of them I deal with by manually pulling. Dr. Joe Neal, professor of weed science at NCSU, recommends a frequency of every two to three weeks. Call me crazy, but I have never minded hand weeding. It feels meditative while I am doing it and afterwards, too, when I look upon my tidy garden.
Unfortunately, hand-pulling does not work for creeping woodsorrel (Oxalis corniculata L.). Even after a good rain and using a weed digger, it is difficult to get the root up on a younger plant. I find it easier to let it grow a bit which gives me more plant above ground to grasp and pull. But allowing any weed time to mature is dicey: weeds multiply so quickly and aside from being unsightly, rob your favored plants of moisture and nutrients in the soil. Encroachment is inevitable with woodsorrel as it spreads by rhizome, stolon and/or rapidly germinating seeds.
I used to view ground covers as boring plantings; something you chose for a spot where it was difficult to grow anything else, or something non-gardeners or commercial properties planted to paint a spot green and call it landscaped. (Pachysandra comes immediately to mind.) But looking out my kitchen window last November at the way a few biennial columbine plants (Aquilegia canadensis) have reseeded so profusely over just a few years and now expertly cover a large part of the ground in one bed (i.e. no woodsorrell there), I am beginning to understand the concept and consider the possibilities.
Ground covers are plants that grow relatively close to the ground and spread freely to create a mass planting. The denser they are, the better they will be at shading the ground, thereby robbing weed seeds or rhizomes in the soil of the light needed to grow. If desired for weed control, seek out evergreen ground covers.
Columbine isn’t traditionally considered a ground cover but it does the job nicely. Some common ground covers are already established in my landscape; pictured below left to right they are: golden creeping jenny (Lysimachia nummularia ‘Aurea’ ), creeping juniper (Juniperus horizontalis ), oregano (Origanum heracleoticum ‘Greek’ ) and Mrs. Robb’s bonnet (Euphorbia amyglaloides, ‘robbiae’).
A blank canvas
My thoughts of “too much columbine” have turned to “need more variety of ground covers.” Ground covers will be the new blank canvas. I am not choosing ground covers instead of more ornamental perennials and shrubs. I am choosing ground covers over open soil or a blanket of mulch which can be expensive and labor intensive when used for large spaces. Rather than fretting over too much columbine, I will consider it a placeholder and an organic mulch. When I am ready to plant something among it, I will simply edit out some columbine and insert a showier ornamental.
Where you have stubborn weeds, consider planting a more attractive ground cover. More plant suggestions appear in the links below.