Spring is finally here and invasive species are starting to emerge.  This Protector’s Featured Spotlight showcases common backyard and dockside invaders that emerge in the spring and general control methods. Along with a guide that features native look-alikes to common invasive plants. 

Overview:

Invasive bush honeysuckle species are often seen growing along roadsides and yard edges as they are one of the first plants to leaf out in the spring.

Most natural communities are susceptible to invasion by honeysuckle, but woodlands are particularly vulnerable, especially if they are already disturbed. Honeysuckle thrives in sunny upland sites, including forest edges, roadsides, pastures, and yard edges.

Honeysuckle can replace native plants in an area by shading and depleting the soil of moisture and nutrients. Seeds are readily dispersed by birds, but the fruits are carbohydrate-rich and do not provide high enough fat content for long flights, causing a negative effect on birds. 

Control Methods:

Manual/Mechanical: Small plants can be pulled by hand in early spring when the soil is moist. Larger plants can be pulled if the roots are loosened with a shovel. Cut plants several times a year until root stores are depleted. Cutting encourages resprouting, so repeated cutting or herbicide application is essential.

Chemical: 

Cut-stump: Cut stems at the base and immediately treat
with glyphosate or triclopyr. 

Basial/Foliar Treatment: A basal bark treatment can be applied year-round, and a foliar treatment can be applied in early spring or late fall. Be sure to follow all label instructions.

Overview:

Wild parsnip is a perennial herbaceous plant. It is often found growing along roadsides and yard edges. The main threat of wild parsnip is primarily to human health as the sap from the plant will irritate the skin and may cause severe burns. 

Wild parsnip leaves resemble the leaves of celery and have two to five sharply toothed paired leaflets that grow along the stem.  Stems are yellowish-green in color with vertical grooves (no red/purple blotches or hairs) and can grow up to 5 ft. tall. 

Flowers begin to emerge in late June and resemble Queen Anne’s lace but are a greenish-yellow color.  Plants die after producing seeds. Seeds can remain viable in the soil for up to four years.

Control Methods:

Manual/Mechanical: 

Manual or mechanical methods of control are not recommended because they will expose the operator to the plant sap and spread seeds. If you must get near the plants use gloves, protective clothing, and eye protection.

Chemical:

Foliar applications of glyphosate work best if applied to the rosette stage in the spring or fall. Keep in mind that glyphosate kills all plants.  Keep it away from desirable plants in the area; read and follow the product label instructions completely.

Several years of treatment may be necessary to bring large populations under control. Continue to scout the area for new plants that may develop from latent seeds.

Overview:

Giant hogweed begins to emerge in early spring. Their leaves differ depending on the life stage; emerging cotyledons have more rounded leaves that emerge from three thin stems, as the plant matures the leaves become deeply ridged and a compound in arrangement eventually forming a rosette after multiple growing seasons; mature giant hogweed plants can grow between 10-15 feet tall with leaves up to 5 feet wide, flowers are white and umbel shaped, and stems have purple blotches and white course hairs.

Giant hogweed has two major impacts, ecological and human health. It suppresses the growth of native plants, which has a negative impact on the animals that depend on them. In addition, direct skin contact with giant hogweed induces extreme photosensitivity, which can lead to severe, slow-to-heal burns and scarring. Costs are incurred for both medical treatment and efforts to keep the plant under control. Over 100,000 seeds per plant are dispersed annually by water, wind, or humans.

Control Methods:

The sap inside the stem of giant hogweed can cause severe burns if it comes into contact with skin. For safety, follow these steps from the NYS DEC website to remove giant hogweed.

Manual/Mechanical: 

Plants may be dug out, but care should be taken to remove most of the roots to prevent resprouting. Although this is the most common type of control, it can be difficult and unpleasant. Always wear protective clothing and avoid getting the sap on your skin.

Mowing does not kill the plant and causes resprouting, but it might be successful if done consistently and persistently enough to starve the roots.

Chemical: 

Foliar treatment: Glyphosate is considered the most effective herbicide and should be used in spring and early summer when plants are less than three feet tall. A follow-up application in mid-summer may be necessary. Use caution around desirable species since it is nonselective. Note: Successful management strategies may require a multi-year effort. Always follow chemical label instructions.

Overview:

Garlic mustard is an invasive herb that emerges in early April and dies by June. Basal leaves of immature plants are dark-green and kidney-shaped with rounded serrated edges. Second-year leaves become more triangular and are arranged alternately along the stem. Leaf stalks of mature plants are hairy. Crushed leaves produce a strong garlic odor and can be helpful when identifying immature garlic mustard plants. Flowers have 3-6 small, white petals that grow in clusters and bloom in May.

Garlic mustard releases chemicals that can inhibit the growth of nearby plants, and hinder beneficial soil fungi which help tree roots take up water and nutrients. 

Control Methods:

Manual/Mechanical: Small infestations of garlic mustard in non-forested settings can be manually removed. This is best done in early spring when the soil is soft and before seeds develop. A chemical herbicide can be applied in areas too large for manual removal.

Chemical:

Chemical application is most effective in the spring when garlic mustard is one of the few plants actively growing; care should be taken if applied in the fall to avoid harming other plants. Be sure to follow all chemical labels. Infestations in a forested area are best left alone, according to the research by Dr. Berndt Blossey at Cornell University. 

Overview:

Curly-leaf pondweed is a submerged aquatic perennial that grows in early spring, and then dies back going dormant in early summer. It is easily identified by its wavy lasagna-like leaves that are olive-green to reddish-brown in color depending on environmental conditions.  Stems are branched and somewhat flattened and grow up to 6 feet long. Before going dormant, flower stalks rise above the surface baring tiny brownish flowers. Bur-like turions are produced at stem tips and germinate in late summer or fall. 

Curly-leaf pondweed grows dense mats that displace native aquatic vegetation and inhibits water recreationists. The loss of native plants reduces biodiversity and the habitat available for spawning fish, waterfowl, and other aquatic wildlife. 

Control Methods:

As with all aquatic plants, controlling curly-leaf pondweed can be difficult. Therefore prevention is the best form of control. Cleaning, draining, and drying watercraft before entering and after leaving new waterbodies significantly reduces the spread of curly-leaf pondweed and other aquatic invasive species.

Manual/Mechanical:

Drawdowns, dredging, raking, cutting and harvesting can all be effective methods of control. There is some evidence that turion production may be prevented or lessened if plants are cut early in the season at the sediment level.

Chemical:

Due to early emergence, herbicide can be used to control curly-leaf pondweed with less of an impact on native plant life. All control methods will require multiple applications and monitoring for several growing seasons. Permits will be required for chemical treatments. 

A regional photographic guide to a broad selection of invasive plants that are often confused with similar native look-alikes. 

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