Identifying invasive plants

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Identifying Invasive Plants

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Click on a link to jump to that species:
bush honeysuckle - Lonicera maackii
Japanese honeysuckle - Lonicera japonica
Non-native privet - Ligustrum sp.
Tree of heaven - Ailanthus altissima Kudzu - Pueraria montana

Bush honeysuckle - Lonicera maackii

Example of the problem: Percy Warner Park, Nashville, TN

Dense undergrowth of bush honeysuckle shades out early-spring herbaceous plants.

Bush honeysuckle has been removed in this area which is adjacent the location shown in the left image.

Native species that might be confused with bush honeysuckle:
coralberry (Symphorocarups orbiculatus) and spicebush (Lindera benzoin)

Comparison of leaves

Bush honeysuckle has opposite leaves that taper to a point.

Coralberry also has opposite leaves, but their tips are more rounded.

Although their tips tend to be pointed, spicebush leaves are arranged alternately on the twig. Crushed spicebush leaves also have a spicy smell.

Comparison of flowers (spring)

Bush honeysuckle - Fragrant, showy white flowers appear after the leaves are present.

Coralberry - Small greenish flowers in July

Spicebush - Small yellowish-green flowers appear in early spring before the leaves have emerged.

Comparison of fruit (fall)

Red bush honeysuckle berries.

Pink coralberry berries.

Red spicebush berries.

Japanese honeysuckle - Lonicera japonica

Example of the problem:

Dense Japanese honeysuckle vines on a stream bank in Radnor Lake State Natural Area, TN.

Japanese honeysuckle covering trees on a roadside in Tennessee

Native species that might be confused with Japanese honeysuckle:
Japanese honeysuckle is a thin, twining vine and is not easily confused with common native vines. For comparison purposes, the most common native vines are: poison ivy (Toxicodentron radicans) and crossvine (Bignonia capreolata).

Japanese honeysuckle leaves are simple and arranged oppositely on the vine.

Poison ivy had three leaflets and the leaves are not paired on the vine.

Crossvine has two leaflets per leaf and the leaves are paired on the vine.

Comparison of flowers

Japanese honeysuckle flowers are showy and fragrant. They are first white and become more yellow with age.

Poison ivy flowers are small and scentless.

Crossvine flowers are large. They are red and yellow.

Japanese honeysuckle fruits are small and black.

Poison ivy fruits are yellowish white and clustered.

Crossvine fruits are an elongated capsule. However, crossvine does not commonly produce mature fruit.

Non-native privet - Ligustrum sp.

Example of the problem: Percy Warner Park, Nashville, TN

On the left side of this trail, non-native privet has been removed. On the right it has not. Like several other invasive plants, non-native privet produces leaves early in the spring, reducing light available for other plants that form leaves later in the season.

non-native privet forms dense, nearly impenetrable thickets.

Removal of non-native privet allows sunlight to reach plants on the forest floor.

Easily confused with the native upland swamp-privet (Foresteria ligustrina).

Non-native privet has glossy, evergreen leaves with no teeth.

The native privet has deciduous leaves with tiny teeth.

Flower (spring)

Non-native privet flower

Foresteria flower image not available

Fruit (fall)

Non-native privet fruit

Foresteria mature and developing fruit

Tree of heaven - Ailanthus altissima

A. altissima can form dense stands. It is a common "weed tree" in urban areas but can also invade disturbed forest areas.

Native species that might be confused with Ailanthus:
sumac (Rhus) species (smooth sumac Rhus glabra, winged or shining sumac Rhus copallinum, staghorn sumac Rhus typhina) and black walnut (Juglans nigra)

Ailanthus leaf

Smooth sumac leaf

Black walnut leaf. Note how leaflets tend to curve.

Characteristic gland near the base of Ailanthus leaflet.

Smooth sumac leaflets are conspicuously toothed (as are leaflets of staghorn sumac).

Winged sumac leaves have a winged rachis connecting the leaflets.

Black walnut leaflets are finely toothed.

Ailanthus leaf scar	Smooth sumac leaf scar	Black walnut leaf scar.
	Sumac twigs produce milky sap when cut.	Characteristic chambered pith in black walnut twig cross section.