Invasive Plants: Reduce the Spread of These Aggressive Plants

Exotic species have been introduced by humans all around the world. Sometimes the introduction is for agriculture, horticulture, or biocontrol of another species. Or the introduction is the unintended consequence of global trade and exploration. Outside of its own native range, an invasive is free from natural controls which exist in its homeland, such as predators, parasites and diseases adapted to prey upon the particular species. Therefore, an invasive species may experience quick and unrestricted growth where it has been introduced.

The decline of almost half of the imperiled or endangered species in the United States is due in part to the spread of invasive species. Our native species have not evolved to cope with the exotic species, and cannot be expected to survive unless something slows the spread of the exotics. The more species comprising an ecosystem, the more stable the ecosystem and its ability to cope with stress or change. However, without intervention, many of the worlds ecosystems will end up dominated by a very few, "super-species", unable to provide for the needs of birds, insects, animals, or humans.

For more information, visit http://www.nps.gov/plants/alien/factmain.htm

**Because U.S. native plants can become invasive outside their natural, historical ranges, be sure to use plant species native to the region in which you live. Check with your local native plant society for recommendations of species and sources of native plants.**

Weed Alert: Akebia

Issued by the Olmsted Parks Conservancy Herbarium

Akebia (Akebia quinata), fiveleaf akebia or chocolate vine, is a twining woody vine or groundcover. This aggressive species spreads primarily through human activity, grows 20 to 40 feet in a single growing season, and thrives in almost every possible growing condition.

Characteristics:

• When young, the plant has green vines which turn brown at maturity. Alternate leaves are divided into 5 oval leaflets that are about 1” to 3” long with a smooth edge.
• The female flowers are plum-colored to brown and about 1” wide, while the smaller, rosy-purple flowers are male. Although the fruit is rarely produced and hard to find, it is a 3” to 5” long, oblong purplish berry with black seeds imbedded in a fleshy pulp.

Please contact Olmsted Parks Conservancy’s Botanist Patricia D. Haragan to report any sightings of akebia, who is helping to document the spread of this species in Kentucky, at Patricia.Haragan@olmstedparks.org. Pat will also provide direction for affective removal of this invasive plant.

Vines

Hedera helix English Ivy

This evergreen climbing vine attaches to the bark of trees, brickwork, and other surfaces using several tiny, root like structures. The leaves are dark green and waxy, and are arranged alternately along the stem. If there is enough sunlight available, umbrella-like clusters of small, greenish-white flowers appear in the fall. In the spring, mature fruits are black with a fleshy outer enclosure containing stone-like seeds. Native plant alternatives include: plantain-leaved sedge, Carex plantaginea; marginal woodfern, Dryopteris marginalis; Solomon’s seal, Polygonatum biflorum; Christmas fern, Polystichum acrostichoides.

Lonicera japonica Japanese Honeysuckle

This perennial vine climbs by twisting its stems around vertical structures, including limbs and trunks of shrubs and small trees. Leaves are oblong to oval, sometimes lobed, have short stalks, and occur in pairs along the stem. Flowers are tubular, with five joined petals, white to pink, turning yellow with age, very fragrant, and also occur in pairs along the stem. Stems and leaves are sometimes covered with fine, soft hairs. Japanese honeysuckle blooms from late April through July and sometimes into October. Small black fruits are produced in autumn, each containing 2-3 oval to oblong, dark brown seeds about 1/4 inch across. Possible native plant alternatives include: Leatherflower, Clematis viorna; trumpet honeysuckle, Lonicera sempervirens; sweetbay magnolia, Magnolia virginiana;

Vinca minor, Periwinkle

This trailing, evergreen vine has shiny, dark green leaves which occur opposite one another along the stem. In the spring, a funnel shaped, violet, five-lobed flower appear singly where the leaf joins the stem. A white star can often be seen in the flower. Possible native plant alternatives include: crossvine Bignonia capreolata; trumpet honeysuckle Lonicera sempervirens; American bittersweet Celastrus scandens.

Celastrus orbiculatus Oriental Bittersweet

The leaves of this deciduous, woody, perennial vine are glossy, rounded, finely toothed and arranged alternately along the stem. Clusters of small greenish flowers appear where the each leaf joins the stem, allowing the plant to produce large numbers of seeds. When mature, globular, green to yellow fruits split open to reveal three red-orange, fleshy enclosures of the seeds. These showy fruits have made oriental bittersweet very popular for use in floral arrangements. This plant is easily confused with our native climbing bittersweet vine, which flowers at the tips rather than along the stems: it is important that each plant is correctly identified. American Bittersweet, Celastrus scandens, is a possible native alternative.

Akebia quinata, Five-Leaf Akebia

This twining woody vine grows has thin, rounded stems that are green when young and brown when mature. The alternate leaves are divided into five or fewer parts called leaflets which are arranged around a central point. The fragrant flowers which appear in late March to early April are chocolate-purple colored, and are often concealed by new foliage. In early fall, violet-colored flattened fruit pods contain a whitish pulpy core with many tiny black seeds. Native alternatives include trumpet honeysuckle Lonicera sempervirens and cross vine Bignonia capreolata.

Ampelopsis brevipedunculata, Porcelainberry

This deciduous, woody, perennial vine twines with the help of non-adhesive tendrils that occur opposite the leaves and closely resembles native grapes. The leaves are alternate, broadly ovate with a heart-shaped base, palmately 3-5 lobed or more deeply dissected, and have coarsely toothed margins. The inconspicuous, greenish-white flowers with "free" petals occur in June through August (in contrast to grape species that have flowers with petals that touch at tips). Fruits appear in fall and are colorful, changing from pale lilac, to green, to a bright blue. A possible native alternative is gray dogwood, Cornus racemosa.

Euonymus fortunei Wintercreeper

This evergreen, clinging vine can form a dense groundcover or shrub to 3 feet in height, or climb 40-70 foot high vertical surfaces with the aid of aerial roots. Wintercreeper has dark green, shiny, egg-shaped leaves, with toothed margins and silvery veins, which occur in pairs along the stems. Stems are narrow and have trailing roots. Clusters of greenish-white flowers appear on a long stalk and bloom from June to July. In the autumn, pinkish to red capsules appear and later split open to expose seeds enclosed in a fleshy orange seed coat. Possible native plant alternatives include: crossvine Bignonia capreolata; trumpet honeysuckle Lonicera sempervirens; American bittersweet Celastrus scandens.

Shrubs

Lonicera maackii Bush Honeysuckle

Exotic bush honeysuckles are usually deciduous shrubs that range from 6 to 15 feet in height. The 1-2 ½ inch, egg-shaped leaves are opposite along the stem and short-stalked. Older stems are often hollow. Pairs of fragrant, tubular flowers appear where the leaf joins the stem. Flower color varies from creamy white to pink or crimson in some varieties. Flowering generally occurs from early to late spring, but varies for each species and cultivar. The fruits are red to orange, many-seeded berries. Native alternatives include: spicebush, Lindera benzoin; Winterberry Ilex verticillata; Rough-leaved Dogwood, Cornus drummondii.

Ligustrum sinense Privet

Leaves of this shrub are smooth, dark green, and one to two inches in length. White, funnel shaped flowers with four spreading lobes appear in June. Dark blue, almost black berries, appear in the fall. Branchlets are thin and gray, densely hairy in some species. Native alternatives include: spicebush, Lindera benzoin; Winterberry Ilex verticillata; Rough-leaved dogwood, Cornus drummondii

Trees

Tree of Heaven could easily be confused with Sumacs or Walnuts, look for the differences...

The base of Tree of Heaven leaves has notches, or glands. The bark of a Walnut Tree has deeper crevices, or furrows. If you remove the leaves from a Tree of Heaven, you will notice a pungent smell. There are more differences (seeds vs. fruit, leaf size, etc.) but these are a couple tell tale signs. We keep Sumacs and Walnuts, so if you’re not sure, please ask.

Herbs

Alliaria petiolata Garlic Mustard

Garlic mustard is a biennial herb with stalked, triangular to heart-shaped, coarsely toothed leaves that give off an odor of garlic when crushed. A rosette of green leaves close to the ground appears as first year plants become established. Through the winter, rosettes remain green then develop into mature flowering plants the following spring. Flowering plants of garlic mustard reach from 2 to 3-1/2 feet in height and produce clusters of small white flowers, each with four petals in the shape of a cross.

Erect stalks of dry pale, brown seedpods hold viable shiny black seeds which mature in May.

Entire plants may be dug up using a hand trowel. Once removed from the soil, plants should be placed in a sealed bag for disposal to prevent seed dispersal.

Recognition of garlic mustard is critical. Several white-flowered native plants, including toothworts (Dentaria), sweet cicely (Osmorhiza claytonii), and early saxifrage (Saxifraga virginica), occur alongside garlic mustard and may easily be mistaken for it.

These lists have been revised to provide you with the names of species which are either currently considered to be invasive in Kentucky, or are invasive in many of our surrounding states and could become invasive here as well. In any given part of the world, plants which are considered to be invasive will vary. The images and information contained on these pages are courtesy of employees of the Louisville Olmsted Parks Conservancy, the National Parks Service, the Native Plant Alliance, and the Alien Plant Working Group. Please visit http://www.nps.gov/plants/alien for more information.

Plant Invaders of Parks & Natural Areas: Herbs

• Garlic mustard (Alliaria petiolata)
• Giant reed (Arundo donax)
• Musk thistle (Carduus nutans)
• Purple loosestrife (Lythrum salicaria)
• Japanese stilt grass (Microstegium vimineum)
• Eurasian watermilfoil (Myriophyllum spicatum)
• Common reed (Phragmites australis)
• Japanese knotweed (Polygonum cuspidatum)
• Common mullein (Verbascum thapsus)

Plant Invaders of Parks & Natural Areas: Trees

• Tree-of-heaven (Ailanthus altissima)
• Silk tree (Albizia julibrissin)
• Paper Mulberry (Broussonetia papyrifera)
• Princess tree (Paulownia tomentosa)
• White poplar (Populus alba)
• Common buckthorn (Rhamnus cathartica)
• Black locust (Robinia pseudoacacia)
• Salt cedar (Tamarix species)
• Siberian elm (Ulmus pumila)

Plant Invaders of Parks & Natural Areas Vines

• Fiveleaf akebia (Akebia quinata)
• Porcelainberry (Ampelopsis brevipedunculata)
• Oriental bittersweet (Celastrus orbiculatus)
• Climbing euonymus (Euonymus fortunei)
• English Ivy (Hedera helix)
• Japanese honeysuckle (Lonicera japonica)
• Mile-a-minute (Polygonum perfoliatum)
• Kudzu (Pueraria montana var. lobata)
• Wisterias, exotic (Wisteria floribunda and sinensis)

Plant Invaders of Parks & Natural Areas: Shrubs

• Silk tree (Albizia julibrissin)
• Japanese Barberry (Berberis thunbergii)
• Russian-olive (Elaeagnus angustifolia)
• Bush honeysuckles, exotic (Lonicera spp.)
• Common buckthorn (Rhamnus cathartica)
• Multiflora rose (Rosa multiflora)
• Wineberry (Rubus phoenicolasius)