Gardeners Go Wild Over Weeds

Gardeners Go Wild Over Weeds

By Master Gardeners Elizabeth Adlung, Sheila Salmon, and Sue Conrad, Master Gardener Trainee

“Cursed is the ground because of you; through painful toil you will eat of it all the days of your life. It will produce thorns and thistles for you, and you will eat the plants of the field. By the sweat of your brow you will eat your food until you return to the ground,” Genesis 3:17-19

“To thy fair flower add the rank smell of weeds: But why thy odour matcheth not thy show, The soil is this, that thou dost common grow.” Those parts of thee that the world’s eye doth view. — William Shakespeare

Pike County Master Gardeners can be a very opinionated group. Just ask a few of them about things like mulch, how to grow tomatoes, compost, and plenty of other gardening and horticultural topics. You’ll have as many opinions as you have gardeners! But gardeners get really wound up when you ask them about weeds. I bravely asked a few Master Gardeners (MG) “What is your least favorite weed and why.” Their responses were heated, indignant, annoyed, and verbose. A weed is largely a matter of opinion.

Wikipedia says, The term weed in its general sense is a subjective one, without any classification value, since a weed is not a weed when growing where it belongs or is wanted. Indeed, a number of “weeds” have been used in gardens or other cultivated-plant settings.

This article will describe a small sample of the weeds Master Gardeners in Pike know and hate — Mugwort, Goutweed, Bindweed, Stiltgrass — and what they do to control them. From time to time, Master Gardeners will publish more information on other Pike County weeds and weed control.

Mugwort

“It’s insidious!” exclaims Gretel Walker talking about mugwort (Artemisia vulgaris). “Such a mass of roots that you can’t dig it out. If you leave one tiny piece, it starts from that and sends out seeds as well.”

Mugwort, also known as Common Wormwood, Felon Herb, Chrysanthemum Weed, Wild Wormwood, or St. John’s Plant (not to be confused with St John’s wort) grows three to six feet tall, with a woody root. It is native to temperate Europe, Asia, and northern Africa, but is also an invasive weed in North America (especially Gretel’s garden). It grows all over Pike County on nitrogenous soils in uncultivated areas and roadsides.

Fact: Mugwort is called chornobyl in Ukrainian, and has given its name to the abandoned city of Chornobyl (Chernobyl in Russian).

Goutweed or Bishopweed

“Roundup® doesn’t even work!” Elaine Haines exclaims, “It chokes out everything else and self-sows by seeds or runners. I have it where my bulbs are, and when I dig it out, the bulbs come with it. The variegated form — snow-on-the-mountain — used as a groundcover isn’t so invasive.”

Goutweed, once thought to heal gout and arthritis, is in the carrot family (Apiaceae) and grows in shady places. It is also called herb gerard, bishop’s weed, and sometimes “ground elder” and confused with elder (Sambucus), an unrelated genus.

In some areas, this plant is considered among the worst of weeds, readily spreading over large areas of ground by underground rhizomes. It is extremely invasive and crowds out native species. The smallest piece of rhizome left in the ground will quickly form a sturdy new plant, followed by many more. If a small plant finds its way into an ornamental perennial flower garden, it will spread with vigor, resist all attempts at eradication, and make continued ornamental gardening there very difficult.

Bindweed

According to MG Jeffrey Seeds, “Bindweed throws roots over twenty feet – impossible to control!”

Field bindweed, Convolvulus arvensis, is a native of Eurasia and was first documented around 1884. By the first quarter of the twentieth century, field bindweed was proclaimed the worst weed in California and many of the western states. It most likely arrived in the United States as a contaminant in farm and garden seeds. However, because of its flowers and climbing nature, some seeds were probably planted as ornamentals, either as a ground cover, in hanging baskets, or on trellises. Field bindweed has been given many names, including perennial morning glory, creeping jenny, bellbine, sheep-bine, and corn-bind.

The following description of bindweed excerpted from http://www.ipm.ucdavis.edu explains why this plant is so hard to get rid of:

The root system has both deep vertical and shallow horizontal lateral roots. The vertical roots can reach depths of twenty feet or more. However, 70% of the total mass of the root structure occupies the top two feet of soil. Most of these lateral roots are no deeper than one foot. Experiments on bindweed have shown that its root and rhizome growth can reach 2-1/2 to 5 tons per acre.

Field bindweed is a hardy perennial that spreads from an extensive rootstock as well as from seed. Most parts of the bindweed roots and rhizomes can produce buds, which can create new roots and shoots. Roots capable of budding are found to depths of fourteen feet. Fragments of vertical roots and rhizomes that are as short as 2 inches can form new plants. Lateral roots serve another important function At about 15 to 30 inches from the parent plant, a lateral often turns downward, becoming a secondary vertical root, and sends out both roots and shoots from the turning point. By this means, a single field bindweed plant can spread radially more than 10 feet in a growing season. This extensive underground network allows for overwintering without foliage, and it can persist for many years in the soil.

One to four dark brown seeds are produced in round, smooth, 1/4-inch capsules. An average plant produces about 550 seeds. Within one month after forming, the seed coat matures and becomes impervious to water. Seed that issixty years old has been found to be alive, and the seeds are commonly found in the soil seedbank. Once the seed coat is weakened, seed will germinate at temperatures of 41° to 104°F.

Stiltgrass

In a recent e-mail to fellow Master Gardeners, Sheila Salmon asked, “Does anyone know a safe way to dispose of bags of stiltgrass that I collected last summer and fall?”

MG Marlene Gioia-Smickle replied, “The answer to the stiltgrass question is BURN IT!!! This will kill seeds and all. Hopefully, it is in paper bags so that you can burn bags and all. If not, try to make sure that all of the seeds get into the fire.”

Microstegium vimineum, commonly known as Japanese stiltgrass or Nepalese browntop, is an annual grass that is common in a wide variety of habitats and is well adapted to low light levels. It is native in much of South and East Asia. It can be found from Iran in the west, east to China, and south to the Philippines. It typically grows to heights between 40 and 100 cm (1.5 to 3.5 feet) and is capable of rooting at each node. The plant flowers in late summer and produces its seeds shortly thereafter.

The plant was accidentally introduced into the U.S. state of Tennessee around 1919 and is assumed to have entered from packing material used to ship porcelain from China. Since that time it has become a highly aggressive invasive species and is present in most of the eastern states, more than half of which it has been reported to be invasive.

M. vimineum can out-compete most North American native species. Whitetail deer, which prefer to eat native species of grass, exacerbate the problem because competition is reduced for the exotic plant. Seeds remain viable for five years or more and have high germination rates.

Management and Control of Weeds

Controlling most weeds is not an easy task as any gardener can tell you. Usually, it cannot be accomplished with a single treatment or in a single season. Effective control depends on many factors: the weed itself, where it is located (home garden, food crop, lawn, etc.), time of year, and many other factors unique to each weed plant.

Simply spraying “weed killer” is NOT a good idea. Basically, any weed control method requires one or more of the following:

Cultural methods

Organic mulches (manures, wood chips, grass clippings, etc.) derived from plant material decompose naturally in the soil. Inorganic mulches (plastic sheeting, which does not decompose and therefore must be removed from the soil after serving to increase soil moisture retention) enhance soil warming and reduce weeds.

Mechanical methods

Removal by hand or cultivation can be used to rid the garden of weeds. Weeds that emerge after planting should be removed early before they are past three inches tall. Large weeds are difficult to remove without uprooting vegetable plants. Early season competition which may reduce crop growth, yield, and quality may also occur if weeds are allowed to remain past the three inch stage.

Chemical methods

Herbicides are another weed control aid that some gardeners employ. Gardeners should be aware that no single herbicide will do the entire job of controlling weeds in all vegetable crops. There is also a problem of applying relatively small amounts of the herbicide evenly to the garden surface. Miscalculation of rates or miscalibration of application equipment can cause some areas of the garden to get too much or too little of the herbicide. Under-application will result in poor weed control while over-application will result in damaged plants.

Your Penn State Agricultural Extension office is perhaps the best source of advice for what to do about your weed problem. Decades of scientific research are available to gardeners and home owners in Pike County with just a phone call to (570) 296-3400. Master Gardener volunteers answer your questions about weeds using their own knowledge and the resources of Penn State.

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