University of Maryland Extension

Invasive Shrub Control

 

Autumn olive (Elaeagnus umbellata)

This large shrub or small tree was planted extensively for wildlife habitat, windbreak, and land reclamation. Flourishing in very poor and disturbed soils, it invaded fields and open woodlands, out-competing native plants, creating dense shade, and disrupting plant succession and nutrient-cycling. Although birds do feed on the berries, bird species are more diverse among native vegetation. Other animals and insects are not known to feed on it. P/D (include all root), C& P/S, PostE - see key below

Barberry/Japanese barberry (Berberis thunbergii)

Japanese barberry was promoted to replace European barberry when the latter was found to be a host for black stem rust on wheat. Its popularity soared with new purple and yellow cultivars. Tolerant of shade or sun and producing berries with a germination rate near 90 percent, it has spread into the forest and most other habitats. It also sprouts from root pieces or tip roots. It alters ecosystems by raising soil pH, changing soil nitrogen levels and biological activity, and reducing litter depth. Because deer avoid it and consume native shrubs, it is fast becoming the principal understory plant in parks and natural areas. P/D, F/S, WW, C/MreC, PostE, C&P/S -see key below

Read more: CSI: The case of docile garden plant that runs amok! Or, Much Ado About Barberry

Euonymus/winged euonymus/burning bush (Euonymus alatus)

Berries of this Asian ornamental invade sunny or shady habitats where it can form monocultures. Virtually nothing grows underneath except its own seedlings. Do not confuse it with native euonymus called strawberry bush or hearts-a-burstin’ which does not have corky ridges or “wings” on the stems. P/D, F/S, C/MreC, C&P/S - see key below

Honeysuckle shrubs—including Amur, Bell’s, dwarf, fragrant, Morrow’s, Standish’s and Tartarian (non-native Lonicera species)

These Eurasian bush honeysuckles were grown for flower and fruit as well as erosion control. They displace natives and form monocultures. The prolific carbohydrate-rich berries are relished by birds but do not provide the fat content birds need for migrating great distances. Flowers compete with native plants for pollinators, causing reduced seed set for native species. Root toxins may inhibit other plant growth. It has hollow stems, unlike native honeysuckles. P/D, C/M/reC, C&P/S, PostE, B - see key below

Multiflora rose (Rosa multiflora)

This Asian rose chokes out natives. Flowers are white (native roses are usually pink). It grows impenetrable stands in sun or shade and can climb trees. Disturbed or neglected areas are quickly colonized by it. Birds spread the seeds. Branches layer where they contact soil. P/D, C/M/reC, PostE with spreader sticker, C&P/S - see key below

Privet (all Ligustrum species)

Grown primarily as hedges, privet has escaped to many habitats but needs sun to produce berries. Its dense thickets out-compete native plants. P/D, PostE, C&P/S - see key below

Wineberry (Rubus phoenicolasius)

With tasty raspberry-like fruits, the Asian wineberry is still used as breeding stock and enjoyed for its fruit. In the wild, its vigorous growth crowds out natives and covers extensive areas. Distinguish from other bramble canes by its many red hairs among its small spines which make the cane appear red, almost furry. It prefers moist soils and sun and spreads by berry seed and tip rooting. P/D, C/M/reC, C&P/S - see key below

Key for Control Methods

Mechanical Options

  • (B) Burn: Use controlled fires to destroy aboveground growth. (First, contact local fire department).
  • (C&G) Cut and grind:  Cut down, then grind stump.
  • (C/M/reC) Cut, Mow, and Re-cut:  Cut to the ground and re-cut at the first appearance of new growth.  This starves the root system. It may require persistence.
  • (F/S) Flower/Seed removal Do not allow seed development.  When plant removal must be postponed, prevent spread by seed. Cut off flowers before seed forms. Some plants flower and produce seed at the same time. Bag and dispose of seeds in landfills.  DO NOT compost.
  • (G) Girdle:  Remove bark and cambium layer.  Remove (or spray) any re-sprouting from roots or below girdled area.
  • (P/D) Pull/Dig: This is especially effective with seedlings or annuals. Mile-A-Minute vine, for instance, has almost no root system at all.  However, for those that can re-sprout from a tiny root piece, such as Canada thistle, removal of entire root is critical. Moist soil facilitates.
  • (SM) Smother: Cover plants with cardboard, many layers of newspapers, or plastic, then mulch. Plastic must be removed afterward, and if mulch decomposes on it, this can be an arduous process.
  • (WW) Weed Wrench (TM):  This tool can uproot large shrubs and small trees

Chemical Options

  • (C&P/S) Cut and Paint or Spray:  Cut down trunk and paint or target spray the stump within five minutes.
  • (H/S) Hack & Squirt:  Slash bark using a saw or hatchet, and squirt liquid herbicide into the wounds; re-spray any re-growth. 
  • (PostEPost-emergent herbicides:  Spray foliage of perennial/woody plants. Spot-treat in lawns.
  • (PreE)Pre-emergent herbicide:  Spread this granular herbicide prior to seed germination. 

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