Landscape - Honeysuckle Control

Japanese honeysuckle is a common invasive weed in Delaware. The following are some control recommendations.

Japanese Honeysuckle, Lonicera japonica, is in flower across Delaware. Leaves are mostly oval to somewhat lobed, opposite, in pairs. Honeysuckle often remains evergreen through the winter. Flowers are tube shaped, white to pink, turning yellow with age and occur in pairs along the stem at leaf axils. They have a distinctive fragrance. This invasive woody vine is common along wood edges, ditch banks, roadsides, fence lines, low maintenance areas, and right of ways. It was introduced in the early 1900’s from the Far East. It is an aggressive climber and can smother desired shrubs and trees and cover fences or posts.

Control small patches by hand digging. Mowing repeatedly is partially effective on large areas. Mow twice, one in July, again in September and repeat each year. In areas where it is climbing vegetation,cut at the base and remove vines. Apply a herbicide to cut stems. Use a 50% glyphosate herbicide or 25% triclopyr herbicide solution (based on formulated products such as Roundup or Garlon). Foliar applications of a 1-5 to 2.5 % glyphosate or a 2% triclopyr herbicide (formulated product) sprayed to runoff can provide control but repeated applications may be needed. Treat in the fall, when non-target plants are going dormant. Avoid contact with desired plants that are still in leaf.

Gordon Johnson, Extension Horticulture Agent, UD

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:
http://www.delawareinvasives.net/yahoo_site_admin/assets/docs/Mistaken_Identity.5855244.pdf