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Shaw Nature Reserve Native Landscaping Manual Chapter Three - Control and Identification of Invasive Species A Management Guide for Missouri Table of contents: Order Chapter Three in booklet form IntroductionThroughout the United States, invasive plants are destroying native ecosystems and landscapes as they out-compete native plants for light, nutrients and moisture. Most of these invaders purposely were brought to the United States from other parts of the world for reasons that include ornamental value, livestock forage, erosion control, and food for wildlife. Some arrived accidentally as part of ship cargo, embedded on animals, clinging to clothing and other means. Whatever the means of entry, when these plants entered the U.S, their spread was unimpeded by natural enemies, such as grazing animals, insects, diseases, that kept them in check in their homeland. Unregulated, they spread rapidly and wreak havoc on biodiversity as they overtake landscapes that once provided shelter and food for native wildlife. Among the worst offenders are bush honeysuckle, wintercreeper, autumn olive, sweet clover, Japanese honeysuckle, purple loosestrife, garlic mustard, sericea lespedeza, Japanese hops, and Johnsongrass. The severity of infestation ranges from a few plants in a backyard to acres filled with dense populations of undesirable species. This guide includes control measures that can be used by homeowners and professional land managers. Homeowners likely will be able to use simple, mechanical methods, while professional land managers likely will resort to methods that call for herbicide application and use of large equipment. Herbicides suggested in this manual are low risk and are not apt to contaminate groundwater. They break down rapidly in the environment and have low toxicity to animals.
(Above left, A volunteer pulling sweet clover after rainfall. Below left, Crown vetch planted along interstate. Right, Honey suckle thicket in mature forest.)
Points to remember when controlling invasive species Create an application strategy before applying herbicides. Herbicides should be used in conjunction with other methods, such as hand pulling, mowing, controlled burning, reseeding and/or planting native alternatives. It is easier to control invasive species before they get out of control, so control early. When dealing with a large population of an invasive species, begin removal at the edges and work inward. This reduces the rate of spread. Personnel should be trained on herbicide and equipment use and should be able to identify target and non-target species. Prevent contamination of streams, ponds, and lakes by selecting herbicides that degrade rapidly in the soil and by using the right amount of herbicide for the job. Use approved herbicides when applying near water and prevent spills, drips, and non-target drift. Do not buy invasive plants. Many nurseries sell invasive plants such as wintercreeper, periwinkle, burning bush, autumn olive, purple loosestrife and crown vetch. Replace invasive species with appropriate native plants (see Chapter 1, Reconstructing a Tallgrass Prairie). There are native alternatives available for each of the invasive plants mentioned in this guide. Effective control may take several years. Scout annually for sprouts of invasive plants and remove immediately.
This guide: Will help identify and effectively control invasive species. Will describe how to remove mechanically invasive species in small landscapes. Will describe how and when to apply herbicides for large landscapes. Will suggest native plant alternativs for invasive species. And will demonstrate how to manage land to prevent the invasion or re-invasion of invasive species.
Terms to Know
Mechanical Control Methods of Invasive Species
Newly emerged seedlings of woody plants are easily hand-pulled when soil is moist (a day or two after rainfall). Stems less than one inch in diameter can be cut with sharp hand pruners or loppers***. Then use a weed wrench, winch, or come-along to yank the roots out of the ground. If this is not an option, dig out roots with hand tools or rent a stump grinder.
Hand prunners, hand saw, and loppers
***The most common injury among horticulturists and volunteers at Shaw Nature Reserve is a cut to the opposite hand when using hand pruners. Practice apropraiate safety measures at all times.
Stems more than an inch in diameter typically require a handsaw, chain saw, or a string trimmer outfitted with a circular saw blade. Chain-saw and circular-saw use require training and proper safety gear (helmet, ear and eye protection, leg and ankle protection, and sturdy leather boots).
For large shrubs and trees, remove trunks and stems first. Then roots are more easily removed. Leave 1-3 feet of stem attached to the roots to use as a handle or lever and use a weed wrench, winch, or come-along to yank out the roots. If this is not an option, dig out the roots with hand tools or rent a stump grinder.
Large-scale removal (more than an acre) requires a skid-steer and front-mounted root grapple or bull hog to remove mature shrubs, roots and all. Some grapples grab the stems and pull up, others grab the roots and pry out. Skid-steer removal should be done only when the ground is dry to keep soil disturbance to a minimum. Disturbed ground quickly grows with weeds, so have a native plant seed mix ready to sow in these areas. See section on revegetation to prevent secondary invasion of weeds.
Grapple-device on a skid-steer
When to Apply Herbicides
Seasons to apply:
Seasons to avoid:
Apply Herbicides when Weather Conditions Permit
Safety Requirements
(Top Left: Protective gear includes safty glasses, rubber gloves, and tyvec suit. Top Right: Avoid spills and use care when pouring concentrated herbicides. Bottom Right: Always label unused herbicides.)
How to Read an Herbicide Label
If you read an herbicide label, you will see that it lists a percentage of active ingredient. For example, if herbicide A contains 50% active ingredient, then it is a 50% concentration of that herbicide A. If the recommended concentration of herbicide A is…
Herbicide Application Methods for the Removal of Invasive Plants Foliar Treatment: Spot spraying. Used to control most invasive species in this guide. It is recommended for annuals, biennials, perennials and small woody plants (less than 3-4 ft. tall or ½ inch stem diameter). It is recommended when native plants already exist in the treatment area.
Foliar Treatment: Crown spraying or spraying over the top is used on shrubs and vines (more than 4-5 ft. tall or ½ inch stem diameter and less than 10 ft. tall).
Foliar Treatment: Broadcast spraying is used to kill vegetation in old fields, on roadsides and in lawns.
Cut-surface Treatment includes two methods for controlling invasive tree, shrub, and vines. It often is recommended when native plants exist in the treatment area. The treatment is inexpensive and reduces non-target damage. Glyphosate and triclopyr are typically applied at high concentrations using nozzles that have a straight or fan-shaped spray tip to minimize non-target damage. Sub-freezing applications are made possible by substituting window-washing fluid for water or by using oil-based herbicides like Garlon 4 or Pathfinder II. Mix with water-soluble herbicides only.
Above: Stems are cut. Stumps are immediatly sprayed. Left: Brush piles of removed vegitation provide cover for wildlife. Right: The cut stump method.
Cut Stump Method cut stems off close to ground level with lopers or a hand saw and immediately apply concentrated herbicide to the cambial area of the stump (outer edge). For stems smaller than 3 inches in diameter, treat the entire stump surface. For larger stems, apply herbicide to the outer 20% of the stump. The chemical moves to the roots and kills the root system. Delays in application after cutting results in reduced control. Applications are most effective during active growth and full leaf expansion. Winter applications are effective, but herbicide must be applied at a 20% concentration. The Hatchet and Spray Method is used generally for stems larger than 3 inches in diameter using an ax or hatchet. Make uniformly spaced cuts around the base of the stem less than 1 inch apart. Angle cuts downward, going through the bark and into the sapwood. Spray herbicide into each cut. The chemical moves to the roots and kills the root system. Large trees may be left standing after they die.
Basal Bark Treatment is used for controlling large trees, shrubs, and vines when cut surface treatment is not feasible. For large acreage it may be cost-prohibitive to cut and spray thousands of plants. Spraying the bark without cutting stems saves time. Great care must be taken to prevent non-target damage.
Garlon 4 mixed with basal oil or Pathfinder II typically are used for basal bark treatments any time of year except when snow or water prevents spraying the base of the stem. A 20% concetration is needed for effective control. Use a sprayer at low pressure (20-40 psi) that has a straight stream or fan-shaped tip. Low pressure helps prevent non-target damage. Stems should be sprayed on all sides to a height of 1-2 feet from the ground. It may require several months for a single application to kill the target species, but by spring the tree or shrub either doesn't leaf out or dies later in the season. Eventually the roots die, and the plant topples to the ground. Basal treatment is not effective on older trees with thick bark. For larger trees with thick bark, use the hatchet and spray method.
Herbicides and what they ControlMention of trade names is not a brand recommendation.
2,4-D is active against broadleaf plants (perennials, biennials, and annuals) only; grasses are unaffected. This herbicide is used widely for weed control in lawns and other urban settings. In natural areas, 2,4-D can be used to spot spray broadleaf weeds. It can be applied over native grasses to control many invasive species. Glyphosate is a broad-spectrum herbicide that kills most plants within days after spraying (yellowing may be delayed in cool weather). It is used for foliar and cut stump applications. Triclopyr is used widely for the control of woody plants, but also controls broadleaf perennials (does not affect grasses). It is often used in cut-stem and basal-bark applications. Garlon 4 is the oil-based form used in basal bark treatments. Hackberry is highly sensitive to high concentrations of Garlon 4 and Pathfinder II. Sulfosulfuron at low doses is specific for Johnsongrass. Follow label mixing rates carefully because it is highly concentrated. Do not mix with Roundup or other herbicides because it is slower acting. Spray foliage well before flowering or plants may go to seed.
Revegetation and Maintenance After Removal of Invasive Species
In moderately to highly infested treatment areas, sow an annual cover crop immediately after treatment to prevent or reduce erosion and reinfestation of invasive species. A second or third herbicide treatment may be necessary for quality control. You may need to reseed an annual cover crop after each herbicide application. When control is achieved, plant container or bare root native alternatives (see table below) in spring or fall immediately following treatment. If sowing seeds for revegetation, sow in December or January following treatment (See Chapter 1: Reconstructing a Tallgrass Prairie: A Seeding Guide for Missouri for complete seeding directions). Choose native species appropriate to your light, moisture and soil conditions. Long-term Maintenance: Scout treated areas for re-sprout and/or new seedlings. Young seedlings are easily pulled by hand soon after rain or watering. Bush Honeysuckle and Privet are easily visible in October and November because their leaves are yellow and most other shrub leaves have already fallen.
Native alternatives to invasive non-native landscape plants
Major Invasive Species of ConcernAmur or Bush honeysuckle - Lonicera maackii Bush honeysuckle (a woody shrub) is often mistakenly referred to as Japanese honeysuckle, and sometimes confused with privet. The flowers of Amur honeysuckle are faintly fragrant. This shrub was improved by breeding for greater fruit production by the USDA in Missouri, and has been planted for landscaping and attracting wildlife across the eastern US. In fact, bush honeysuckle provides poor quality food and habitat for birds. It thrives from Maryland and Virginia to Missouri and eastern Kansas. Plantings are known to rapidly spread to nearby forests where they can occupy several square miles of wooded areas within 5 years. Similar stories could be repeated all over the St. Louis and Kansas City regions in Missouri. Small infestations can be killed with most wide-spectrum and broadleaf-specific herbicides (RoundUp or Garlon) applied to the foliage at 1.5-4% concentration. Timing is important, with late growing season (September-October) applications often reported to be more lethal than those in earlier or later months. Homeowners should be aware that brush from bush honeysuckle containing berries contains seeds and should not be put into municipal mulch piles to avoid spreading the seed further. Larger individuals are best controlled in fall or winter with either basal or cut stump treatments of Garlon or related herbicides at 20% concentration.
The berries of Amur honeysuckle (above) are attractive to the human eye and are eaten eagerly by migrating and resident birds, which disperse the seeds in their droppings. Japanese honeysuckle - Lonicera japonica Japanese honeysuckle (an "evergreen" woody vine) historically was much-loved in gardens for the delicious fragrance of its flowers. In nature however, it is a plague throughout the Eastern United States. The flowers open white and turn creamy yellow, emitting the fragrance for which they are famed. The fruit is a shiny, black berry that is eaten by robins and other birds that gobble them up and disperse the seeds "down the flyway a piece".
The evergreen foliage can be sprayed in fall and winter when many other plants are dormant. Though death is slow (typically well into the following spring), fall spraying with 1.5-2% Roundup or other common foliar herbicides is highly effective. Japanese honeysuckle resprouts after prescribed burning, but frequent burning reduces their abundance. More importantly, it limits flowering and fruiting. This reduces the establishment of new populations through seeds dispersed by birds and mammals.
Japanese honesuckle in flower (left). The corollas fall away to leave a tiny green fruit that ripens to a plump, black berry in fall (right).
California privet - Ligustrum obtusifolium California privet (a woody shrub) is a species of shiny-leafed, sweet-flowered privets from Asia. Various species of this exotic privet are planted in different parts of North America. All of them have become invasive. California privet has smooth gray bark. Its stems have paired, thorn-like twigs along their lengths. The shiny, dark-green, elliptical leaves are also paired, and only a little over an inch long. Small, white flowers appear in June and are fragrant. They are eagerly visited by pollinators ranging from tiny sweat bees to large swallowtail butterflies. As autumn arrives all the early-summer pollinator activity pays off in the form of a large crop of blue-black berries that birds love. This privet species traditionally has been maintained by heavy pruning into a hedge that does not set fruit and presents little danger of spreading. Unfortunately, once such a shrub is abandoned to grow freely, abundant seed production spread by birds starts an invasion. At Shaw Nature Reserve, the population of this plant, negligible in numbers before 1990, has exploded in the last 15 years. For control methods, see comments on Amur honeysuckle above.
Autumn olive - Eleagnus umbellata This woody shrub was widely planted for its presumed value to wildlife, especially migratory birds who eat the plentiful berries. The fruits and younger twigs are covered with characteristic tan or whitish scales. The upper side of the leaves has a grayish cast and the underside is nearly white. The fine hairs, which cause this gray or whiteness, reduce moisture loss through the leaf surface during hot and/or dry weather. The flowers of autumn olive are produced in profusion in early May and exude a powerful and alluring fragrance. Autumn olive shrubs buzz with pollinating insect life when in bloom.
Autumn olive is killed easily with Roundup or Garlon applied to the foliage of small plants at 1.5-4%. Timing is important, with late growing-season applications generally more lethal. Larger plants are best controlled in fall or winter with either basal or cut stump treatments of Garlon at 20% in paraffin oil or diesel. Freshly cut stumps also may be painted with 20% Roundup with a good kill rate. In cold weather, diluting Roundup with automobile window-washing fluid prevents freezing and may improve penetration into plant tissues.
Wintercreeper - Euonymus fortunei Wintercreeper (an evergreen woody vine) A native of Asia , wintercreeper (a woody vine) is Missouri's most worrisome invasive vine. The plant forms a handsome, solid evergreen ground cover attractive to gardeners and the bright red berries are irresistible to birds. When creeping on the ground, wintercreeper rarely flowers but when it grows to the top of a tree or post it produces plentiful fruits. The first line of defense against wintercreeper is to sever climbing vines to stop them from producing fruit. Be sure to remove a one-inch stem segment.
Wintercreeper is difficult to control because its thick, waxy foliage resists penetration by herbicides. Recent experimentation at the Green Center in St. Louis provides some hope. The waxy cuticle of wintercreeper's leaf wears thin in late summer and this, plus a high level of physiological activity in the plant, are factors that may lead to higher susceptibility to Roundup in September than at other times of year. A single spraying of 1.5% Roundup Pro plus surfactant showed initial efficacy and a small amount of mortality. The experiments indicate that spraying with 1.5% Roundup Pro two September days in a row increases the mortality rate and spraying four days in sequence kills it completely. By comparison, spraying once with 6% Roundup Pro yielded slightly less than 100% mortality. Weedwhipping or mowing wintercreeper to the ground and then spraying immediately with 2% Roundup in July-August has been found effective at the Litzsinger Road Ecology Center.
Wintercreeper is both a spreading but non-reproductive ground cover in the lawn and bushy vine on the tree trunk. Regular clipping of upright stems prevents the invasive vine from dispersing long-distance (and into natural areas) by seeds passing through the digestive tract of birds.
Tall Fescue - Festuca arundinacea Tall Fescue (a perennial grass) was first used in the United States in the late 1800's for pasture improvement. Today it is the most commonly used grass in lawns, pasture, and roadsides in Missouri because it is aggressive and resistant to heavy foot-traffic, grazing, drought, and short-term flooding. Throughout Missouri thousands of acres have been converted from prairie to tall fescue pasture. In the Missouri Ozarks it was promoted as a way to increase pasture productivity and farming income. It also spreads into natural habitats on its own and out-competes native plants. Quail and other ground nesting birds avoid tall fescue fields because they lack sufficient food and are too dense to nest, feed, and take cover in. The seed is dispersed by small rodents, transported on the hooves of large animals and the tires of heavy equipment. More than half of the 100-million-plus pounds of fescue seed sold in the U.S. annually is produced in Missouri, and is a testament to the value of fescue as a lawn grass, roadside vegetation and forage for cattle.
Because it is virtually evergreen, tall fescue is susceptible to Roundup applied any time of year. Grass-specific herbicides are used when desirable broad-leaved plants (eg. coneflowers or blazing star) are co-mingled with fescue.
Sericea lespedeza (a.k.a. Sericea, Chinese bush clover) - Lespedeza cuneata Sericea lespedeza (a perennial herb) is a member of the bean/clover family that has become a pest as a result of an aggressive marketing program. Originally, sericea was promoted widely as food for quail and other small game birds. It turns out that these birds avoid sericea. Also it was promoted as protein-rich forage for livestock though cows will only eat the tender young stems. Lastly it was promoted as a superior erosion control along highways but it turns out to have a coarse root system. Dense-rooted native grasses are far better choice. The saying beware of anything that sounds too good to be true applies here. This tough and prolific weed has diminished the quality of more acres of pasture and corrupted the ecological integrity of more acres of native prairie than any other broadleaved herb in Missouri. While sericea lespedeza is susceptible to many herbicides, it is difficult to control. Seed can live in the ground for over twenty years, which makes reinfestation likely. In addition it often grows nearby desirable plants that may be damaged by herbicide. By spot-spraying individual plants with roundup using low pressure, these problems can be avoided. For treatment of larger populations that are mixed with native grasses, September spraying with Garlon works well (Garlon will not kill native grasses). There are two mechanical methods to deal with sericea lespedeza. First involves mowing with sharp blades shortly after plants bloom in September. This will not kill the plants but will prevent seed development. The only way to control a serious infestation of sericea mechanically is to remove the top 3-6 inches of topsoil. This involves use of heavy machinery such as a skid steer or high-lift. This may well be the only effective method of removal for this incredibly difficult invasive species.
Johnsongrass - Sorghum halepense Johnsongrass (a suckering perennial grass) is increasingly noticeable along Missouri highways and is a concern because of its ability to invade gravel bars, prairie plantings and open floodplain habitats. Its seeds are spread by mowing equipment and in natural areas by flood waters and in mud on the feet of animals. Johnsongrass was imported as a prolific livestock forage though the food value of Johnsongrass is questionable. It is a perennial grass, with stout underground stems (rhizomes) that spread rapidly. The only herbicide that effectively controls Johnsongrass is Outrider. A tiny dose of this chemical kills Johnsongrass and is non-toxic to most other plants (please read label instructions carefully). The herbicide, however, must be applied by licensed applicators. Non-restricted grass herbicides such as Poast and Select are less effective on Johnsongrass, but are more readily available. The only mechanical controls for Johnsongrass include frequent mowing which only prevents seed production and removal of the top 6 inches of soil.
White and Yellow sweet clovers - Melilotus alba, M. officinalis Sweet clover, (a biennial) was originally introduced in the Mid-west as a forage crop and soil nitrogen-builder. Though it has become a serious invasive species, it is still promoted for large animal forage. Sweet clover contains a high amount of coumarins that give them a sweet, pea-like smell. Sweet clover aggressively invades native prairie and open woodland habitats and out-competes native plants by shading them out. It is a common plant along roadsides, fields, and can be a problem plant in prairie reconstruction. Unfortunately use of fire increases seed germination and its ability to spread.
Eradication of a serious sweet clover infestation is very difficult, and control must be ongoing. Treat thick patches of seedlings with Garlon herbicide as the clover is greening up in February-March. The leaf surface of sweet clovers is waxy so use surfactants to prevent water from rolling off the leaves.
Individual seedlings scattered between native plants may be difficult to treat and so herbicide is not recommended. Instead, annual hand-pulling is recommended following a soaking rain when the plants begin to flower (June or July). This method gradually diminishes the soil seed bank of this persistent biennial weed.
Note: In Missouri white sweet clover flowers two to three weeks after the yellow species. If you have infestations of both species, it is recommended to do two weed pullings. First on the yellow and later on white sweet clover. Always deposit seedlings in the trash because seed may ripen in a compost pile.
Burning bush - Euonymus alatus Burning bush is an common woody landscaping shrub that is commonly used in foundation and parking lots plantings and has the potential to spread by seed into nearby woodlands. It is a popular nursery plant because it produces brilliant fall color and handsome winged branches in winter. Unfortunately the berries are loved by birds who carry seeds into nearby natural forests where plants often sucker to form dense thickets. This species became invasive in the St. Louis area only recently and it has proven difficult to control because it does not respond well to herbicides and is difficult to pull from the ground. (seedlings under two feet tall can be pulled after a soaking rain. Suckering sprouts resemble small seedlings and are impossible to hand pull). Larger plants can be dug out with a shovel or mattock but suckers are easily left behind and re-sprout.
Herbicide treatments include cut stump or basal bark methods using roundup pro or Garlon. Please note that cut-stump herbicide treatments alone do not completely kill the roots of the plant so repeat herbicide applications may be necessary. Where populations are so dense that cutting is impractical, foliar applications may be used.
Garlic mustard - Alliaria petiolata Garlic mustard (a biennial) is an invasive plant from Europe that invades natural woodlands. In a forest habitat it often dominates the ground layer over wide areas and has the potential to produce solid stands. It is believed that garlic mustard infestations displace several species of native plants, salamanders, mollusks, and possibly woodland butterflies, ground foraging birds and reptiles. It is considered to be one of the most potentially harmful and difficult to control invasive plants because it spreads so rapidly, produces thousands of seeds and has no natural predators. It tolerates shade and can invade undisturbed natural woodlands or disturbed areas such as trails, roadsides and forests where trees have been logged. Garlic mustard is a member of the mustard family (Brassicaceae). Young leaves smell like garlic when crushed, although the odor decreases as plants grow older. It is a biennial; a plant with a two-year life cycle. The first year it grows in a dark purple to green rosette stage (stemless and low to the ground) and the second year it flowers on a 3-4 foot stalk. Plants bloom March through May with white flowers. The flower is typical of other plants in the mustard family with six stamens: two long and four short. It reproduces only by seed and seeds can remain viable in the soil for up to five years. Seeds are produced in slender, one to two inch long pods. People disperse seeds inadvertently on boots, clothes, mowers, or cars, however birds, small mammals and whitetail deer may also disperse seed. Seeds only germinate in spring after exposure to winter cold.
Hand Pulling
Mowing or String Trimming
Herbicide Control
Because garlic mustard has a 5-year seed bank you will need to monitor for seedlings and resprouting. Repeat control methods for several years until the area is under control and always be on the lookout for new infestations. When control is achieved, plant container or bare root native alternatives in spring or fall immediately following treatment. If sowing seeds, sow in December or January following treatment (See Chapter 1: Reconstructing a Tallgrass Prairie: A Seeding Guide for Missouri for complete seeding directions). Choose native species appropriate to your light, moisture and soil conditions.
Oriental or Asian bittersweet - Celastrus orbiculatus Oriental bittersweet is easily killed with Roundup or Garlon applied to the foliage of small vines at 1.5-4%. Timing is important, with late growing-season applications generally more lethal. Large vines are best controlled in fall or winter with either basal or cut stump treatments of Garlon at 15-25% in paraffin oil or diesel. Freshly cut stumps also may be painted with 15-25% Roundup with a good kill rate. In cold weather, diluting Roundup with automobile window-washing fluid prevents freezing and may improve penetration into plant tissues.
Other Invasive Species of Concern
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