Trees Forever will be hosting an invasive species workshop in cooperation with ISU Extension Forestry and the Iowa DNR. This will be a good chance for local landowners to meet the new ISU Extension Forester Billy Beck. For more information download the Backbone State Park Invasive Species Workshop Event Flier. Read more about Backbone State Park Invasive Species Workshop
One my favorite quotes from Iowa native and conservation icon Aldo Leopold goes like this: “One of the penalties of an ecological education is that one lives alone in a world of wounds.” I think about that quote often this time of year because every fall, after the grand finale of summer recedes to the grays and browns of our dormant winter landscapes, those of us with an ecological education are stuck with a constant reminder of one of our deepest wounds...
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It’s easy to forget they’re mammals just like us. They give live birth, they nurse their young, they feed and sleep and do otherwise mundane things to stay alive and stay healthy. They’re also remarkably easy to forget, going about their lives in caves and forests and only sharing daylight with us in the waning hours of summer evenings. But, let there be no mistaking it, bats are important. And, in light of a long history of changes to forest habitats, new emerging pressures associated with energy development and an exotic disease-causing fungus that’s been wreaking unprecedented havoc on eastern populations in the last decade, many of Iowa’s bats are in trouble....
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Free event! Topics include timber stand improvement, crop tree selection and pruning, invasive species and forest health, and cost share programs available for forestry practices. See Event Flyer for details. See the Iowa Forestry Field Days page for details on other forestry events across Iowa. Read more about Polk County Forestry Field Day (Altoona, IA)
Exotic burning bush (Euonymus alatus) is native to northeast Asia and central China. It was introduced in the United States in the 1860s and it still widely planted today as an ornamental due to its brightly colored fall foliage. Unfortunately, it has spread from landscaping plantings and has become invasive in native habitats. The native burning bush (Euonymus atropurpureus), commonly known as eastern wahoo, is unfortunately lesser known and nurseries and greenhouses often only carry the exotic varieties. Exotic burning bush is a very large dense shrub that can grow in nearly any habitat except those with poorly drained soils. It shades or crowds out native vegetation due to its large, dense growth.
Habitat: Will grow in nearly any area from forest to prairie; doesn’t grow in wet areas. Most common invasions are in wooded areas.
Hardiness: Zone 4
Mature Shape: Large shrub
Height: Up to 20 feet tall
Site Requirements: prefers dry or moist soils; doesn’t grow in poorly drained areas
Leaves: simple, opposite, elliptical, finely toothed, 1-3 inches long, half inch to inch and a quarter inch wide, short petioles, bright pink or red in the fall
Flowering Dates: May to early June
Exotic burning bush is also sometimes called winged wahoo burning bush due to the “wings” that grow on the sides of the twigs. Twigs are green when young, and eventually turn brown. Bark on older plants is smooth; gray on the outside and pale on the inside.
Flowers are one third of an inch across and greenish yellow with 4 petals. They grow in clusters of 3. Fruits are red capsules that open to reveal red seeds.
The native burning bush, eastern wahoo, lacks winged stems and has purple-red flowers instead of greenish yellow flowers.
Avoiding the use of exotic burning bush in landscaping can help prevent their spread into nearby natural areas. Once this plant escapes cultivation, control can be difficult, especially after it has become large and established. Cutting the plant and treating with herbicide is likely the most effective method. Read more about control of burning bush and other invasive species in our Chemical Control of Unwanted Vegetation article.
Common buckthorn or European buckthorn (Rhamnus cathartica) and glossy buckthorn (Rhamnus frangula or Frangula alnus) originated in Eurasia and were brought to the Midwest to be used as hedges and for landscaping. Both species have a long growing season and a dense growth pattern that allows them to out-compete native vegetation. In the fall the yellow leaves on buckthorn plants are easily seen in the understory after most other plants have dropped their foliage. Buckthorn produces many dark berries that either drop to the ground and germinate or are eaten by birds and small mammals and spread across the landscape. Common buckthorn grows in open woodlands and on woodland edges, although it can also be found in prairies, yards, and along roads. Glossy buckthorn can grow in full sun and in heavily shaded areas. Although both species can be found in drier areas, common buckthorn prefers well-drained soils and glossy buckthorn thrives in wet soils. The ability of buckthorns to grow so quickly and in such a wide variety of habitats and soil types makes them particularly concerning exotic invasive species. Additionally, buckthorn is the host plant for soybean aphids, which makes it even more problematic in Iowa. Common buckthorn is listed in Iowa as a primary noxious weed.
Habitat: Both common and glossy buckthorn can be found in a wide variety of habitats from prairies to woodlands though their impacts are greatest in wooded areas.
Hardiness: Zone 3
Mature Shape: Small tree or tall dense shrub
Height: 25 feet
Width: Trunk up to 10 inches in diameter
Site Requirements: Common buckthorn prefers well-drained soils; glossy buckthorn can be found in drier areas but does best in wet soils.
Leaves: Common buckthorn leaves are 1-1.5 inches long, simple, opposite or sub-opposite (occasionally alternate), hairless, round or oval with a pointed tip, and have finely toothed margins. Common buckthorn has 3-4 pairs of veins. Glossy buckthorn leaves are 1-3 inches long, simple, usually alternate, and oblong with smooth margins. Glossy buckthorn leaves have 6-9 pairs of veins.
Flowering Dates: Common: May-June; Glossy: May to first frost
Buckthorn flowers emerge from the leaf axils and are small with white or greenish yellow petals. Common buckthorn flowers have 4 petals and glossy buckthorn flowers have 5 petals. Buckthorn fruit are pea-sized, berry-like, drupes that start out as red and turn black as they ripen in the late summer to early fall. Glossy buckthorn can have branches with fruit in varying stages of ripeness throughout the summer and fall.
Common buckthorn has gray-brown bark that becomes flaky and darker gray-black as the plant ages. Common buckthorn often resembles the bark of plum and cherry trees. Both species have prominent lenticles, yellow sapwood, and pinkish orange heartwood. Common buckthorn has thorns but glossy buckthorn does not.
Removing buckthorn plants early, before they produce fruits is the most effective way to prevent them from spreading. If the plants are still within their first year of growth but there are too many seedlings to remove by hand, prescribed fire in the fall or early spring can be effective. A prescribed fire may need to be performed for two to three years in a row depending if there are seeds in the soil that will sprout the year following the initial burn. Caution should be taken to make sure native plants can tolerate repeated burning. Combining fire with grazing goats can also be effective. Once buckthorn has formed dense thickets, fire is generally not an effective control method. If manual control is not practical, see our Chemical Control of Unwanted Vegetation article for specific herbicides and application methods.
Garlic mustard (Alliaria petiolata) is an herbaceous, biennial forb that was introduced from Europe in the mid-1800s. This highly invasive exotic species grows and spreads extremely quickly, forming thick stands that shade-out and out-compete native understory plants and tree seedlings, to the point of completely suppressing their growth. Additionally, garlic mustard can release allelochemicals into the soil that prevent seeds of other species from germinating. Few animals or insects eat this plant in the U.S., so without human intervention it can spread. One garlic mustard plant can produce hundreds of seeds that remain viable in the soil for 5 or more years. These seeds are easily spread on the fur and feet of animals and through human activity.
Garlic mustard has two different growing phases. In the first year, seedlings have round or heart shaped leaves with scalloped edges that often resemble creeping charlie. In the second year, the plant produces a stalk with triangular leaves that are sharply toothed. Flowers grow at the top of the stalks or in the leaf axils and long, thin, green pods with shiny black seeds form soon after.
Habitat: Forests, along trails, yards, roadsides; prefers shaded areas but can also be found in full sun
Height: First year: 1-6 inches, second year with stalk 1-4 feet
Site Requirements: Cannot tolerate acidic soil
Leaves: Smell like garlic when crushed. First year: round or heart-shaped rosette 1-6 inches across with scalloped edges, not clasped around the flower stalk; second year: sharply toothed triangular leaves 2-3 inches across, alternately attached to flowering stalk
Flowers: small white with four petals that are 0.25 inches wide
Flowering Dates: April-June
Seed Dispersal Dates: July-August
Seed Bearing Age: Produce seeds in the second year of growth (plants die after seed production)
Garlic mustard plants usually have one or two stems but plants that have been cut will sometimes have more. Plants also have a white taproot.
The Iowa DNR has a guide to controlling garlic mustard throughout the year. Prescribed fire can be used in early spring and can be followed up with torching if seedlings continue to emerge. Hand pulling can be extremely effective from April through June, before seeds start falling. It is important to stay out of garlic mustard infested areas from July through October to prevent spreading seeds. Check out our Chemical Control of Unwanted Vegetation article for herbicides and application methods.
Multiflora rose (Rosa multiflora) is native to Japan, the Koreas, and eastern China. It was brought to the U.S. in the mid to late 1800s as an ornamental plant that was valued for its showy clusters of fragrant white to pink flowers. Unfortunately the invasive potential of this plant was not realized until after it was widely used for soil erosion control, living snow fences, highway median barriers, and livestock fences in the early 1900s. Multiflora rose grows very quickly and often forms extremely dense thickets that eliminate nearby plants, reducing understory diversity and limiting growth of livestock forage in pastures. When the arching stems or canes of a multiflora rose plant reach the ground they are able to root and further spread the plant. Additionally, each plant is capable of producing hundreds of thousands of seeds per year that stay viable in the soil for 10-20 years. The fruits and seeds attract birds and small mammals which disperse the plant into new areas. Multiflora rose is classified as a noxious weed in Iowa and multiple other states in the Midwest.
Habitat: Grows in a wide variety of soil, moisture, and light conditions; can be present in wooded areas, pastures, prairies, and along roadsides and stream banks.
Hardiness: Zone 5
Mature Shape: Shrubby with long arching stems
Height: 10 - 15 feet
Width: 9 – 13 feet
Site Requirements: Grows in nearly all soil types but not in standing water.
Leaves: average 2.5 inches long and 0.75 inches wide (can range from 0.5 – 4 inches long), alternate, pinnately compound with 5-11 oval leaflets which have toothed margins, petioles have fringed stipules with glands that look like small red, brown, or black specks.
Flowering Dates: May-June
Multiflora rose flowers are white or pinkish and have 5 petals. Green fruit form in August and turn red and then remain on the plant through winter. Younger stems are green or red and turn gray-brown with age. Larger, older stems turn gray-brown and often have vertical cracks. Stems are round with large curved thorns and generally don’t get larger than one inch in diameter.
Iowa’s native wild prairie rose (Rosa prantincola) does not form dense thickets like the exotic invasive multiflora rose and only grows about 2 feet tall. It also does not have fringed stipules.
The thorns on multiflora rose plants make mechanical control challenging. It is important to remove all of the roots when digging up multiflora rose because new plants will develop from leftover sections of root. Mowing or cutting can be effective if it is done three to six times during the growing season. This must be done for two to four years to be most effective. Combining prescribed fire with other control methods can also be effective. See our Chemical Control of Unwanted Vegetation article for specific herbicides and application methods. Chemical control treatments must also be repeated because the large number of long-lived seeds in the soil will sprout even after the original plant has been eradicated.
Multiple honeysuckle (Lonicera) species can be found in Iowa. The exotic species, including primarily bush honeysuckle (Lonicera maackii) or Tartarian honeysuckle (Lonicera tatarica), originally came from Eurasia. Exotic honeysuckles were used as ornamental shrubs and, before it was clear that these plants would take over so easily, they were planted for wildlife habitat or ground cover meant to prevent erosion. Now we know these plants grow so quickly they out-compete native understory plants, which actually reduces the quality of forest habitat. In contrast, native wild honeysuckle (L. dioica var glaucescens) and grape honeysuckle (L. reticulata), are not invasive and do not form dense thickets like the exotic species.
Habitat: Commonly found in sunny areas such as open woodlands and woodland edges but also in pastures, on the side of the road, and in abandoned fields. Highly disturbed areas such as grazed woodlands are also commonly invaded by non-native honeysuckles. Various species are suited to both upland and lowland habitat types.
Hardiness: Zones 3-6
Mature Shape: The exotic L. maackii and L. tatarica are bushes
Height: 6-18 feet
Site Requirements: most species prefer sun but will tolerate shade, except L. maackii which will grow in full shade
Leaves: simple, opposite, oval, untoothed margins, short petioles; occasionally two leaves will fuse together under the clusters of flowers or fruits
Flowering Dates: May-June
Seed Dispersal Dates: Late summer to early fall
The irregular tubular flowers are pink, white (turn yellow with age), or reddish purple. Exotic honeysuckles have fragrant flowers while native honeysuckles generally do not. The fruit are red or orange berries which are present June-July and October-November. Honeysuckle bark is shaggy and gray or tan in color. Twigs of all species can be hollow. However, the twigs of native species tend to be less hollow with a white pith whereas the exotic species are more obviously hollow with a brown pith.
Exotic honeysuckle leaves emerge one to two weeks before the leaves of native trees and shrubs and don’t drop until later in the fall. This can be useful for identifying honeysuckle invasions in a forest. With their early leaf emergence, exotic honeysuckles are able to shade out native plants and then dominate an area by using up the moisture and nutrients in the soil. Exotic honeysuckles may even release allelochemicals into the soil that prevent other plants from emerging around them.
All chemical or mechanical control of honeysuckle should be conducted before late summer when seeds are dispersed to reduce the likelihood that treated areas will be reinvaded. In the spring, small and medium sized plants can be pulled or dug up. It is important to ensure that plants that have been dug up do not reroot if they are simply laid on the ground. For larger plants it is almost always necessary to use chemical control methods after cutting. See our Chemical Control of Unwanted Vegetation article for specific herbicides and application methods. If an infestation is very small it can be effective to cut the plants several times a year for two years without needing to use chemical control. Prescribed fire can be moderately effective for controlling non-native honeysuckle when used in the spring. Combing prescribed fire with grazing goats can also be effective.
Japanese barberry (Berberis thunbergii) is a small to medium, dense shrub that was originally planted as hedges in landscaping but has spread to native habitats. Japanese barberry is capable of changing soil characteristics in order to help itself outcompete native plants and also has early spring leaf emergence that allows it to shade out any nearby competitors. The native Midwestern barberry Berberis Canadensis and the introduced Berberis vulgaris were successfully eliminated through a federal eradication program because they are able to host black stem rust, which kills small grain crops. Japanese barberry is not a host for this agricultural pest so efforts to eliminate it due to its invasive nature have been less systematic and efficient.
Habitat: Woodlands, trails, roadsides, fencerows, pastures, bottomlands, and highly disturbed areas
Hardiness: Zone 4
Mature Shape: Shrub
Height: 2-8 feet
Site Requirements: Shade tolerant; grows in various soil types but does best in well-drained soil
Leaves: simple, alternate, oval, untoothed with elongated petioles, 0.5 to 1.5 inches long; grow in clusters; turn yellow, orange, red, or purplish in the fall
Flowering Period: May
Japanese barberry twigs are ridged with spines. Newer twigs and stems turn reddish in the winter and become gray as they age. Inner bark is yellow on the branches and roots.
Flowers are one-third of an inch wide and are yellow. They can be single or can grow in small clusters of 2-4 with stems coming from a single point. Japanese barberry produces small, bright red, egg-shaped berries which remain on the plant even after the leaves have fallen.
Use of Japanese barberry and other invasive species in landscaping contributes to their spread into natural areas. Avoiding the use of these species is the first step to helping control their invasion.
In addition to spreading through seed dispersal, Japanese barberry is able to form rhizomes (underground horizontal stems) and spread via roots so it is necessary to remove all connecting roots when digging the plant up. Once large plants are removed, regular mowing where possible can be effective. Spring prescribed fire can also be used for control. Even after plants have been removed treatment may have to be continued for a few years as seeds sprout. See our Chemical Control of Unwanted Vegetation article for specific herbicides and application methods.
