Tuesday, May 26, 2009

Landscape - Know Your Invasive Species 2

This is the second in a series on recognizing invasive species in Delaware. This post is on Asian honeysuckles.

Asian Bush Honeysuckles; Lonicera maackii, L. morrowii, L. tatarica; Honeysuckle Family (Caprifoliaceae)

Form: Deciduous Shrubs
Flowers: May–Jun
Fruits: Jun–Jul, Oct–Nov (L. maackii)

Native Range: China, Manchuria, Korea
Introduction: Tartarian in 1700s, Amur and Morrow’s in late 1890s. Promoted by USDA for wildlife habitat and shelterbelts.
Mid-Atlantic Range & Habitats: Open woodlands, old fields, forest edges, hedgerows, throughout the region.

Ecological Impacts: Several similar species of bush honeysuckles of Asian origin occur in our region. These shrubs leaf out early in the season and hold their leaves longer than most native deciduous shrubs, thus reducing light availability to other plants for a long period of the growing season. Recent studies have shown that chemicals in L. maackii are capable of inhibiting germination of other plants. The nesting success of birds nesting in Asian bush honeysucklesmay be reduced because the plants provide less protection fromnest predators. In addition, foraging birds choose honeysuckle fruit as readily as some native species with greater caloric content. Honeysuckle seedsmay be dispersed over long distances by birds and deer.

Identifications: In the invasive honeysuckles, leaf margins are entire, the fruit a red (usually) to yellowish round berry, and the stem has a hollow pith (the hollow in the center of the pith is often quite small). The invasive species are often confused with native honeysuckles. The yellow flowers of our native Bush-honeysuckle (Diervilla lonicera) are in groups of 3–7 and turn reddish with age. The invasive honeysuckle species all have white to yellow flowers, with the exception of Tartarian Honeysuckle (Lonicera tatarica) that can have white to pink flowers.

Tartarian honeysuckle. Photo by John M. Randall, The Nature Conservancy, Bugwood.org.

Information from "Mistaken Identity - Invasive Plants and their Native Look-alikes, an Identification Guide for the Mid-Atlantic" by Matthew Sarver, Amanda Treher, Lenny Wilson, Robert Naczi, and Faith B. Kuehn. You can download the publication at:

No comments: