Invasive Plants: Removal and Control

They’re called “invasives” for a reason. These plant species are fast-growing, quick-spreading, and resistant (or immune) to natural controls like insects, disease, and animals.

They spread uncontrollably, overwhelming the native flora that aren’t able to compete for resources. And the damage they do to surrounding ecosystems can harms plants, animals, and humans.

The most worrisome invasives in Minnesota

buckthornCommon Buckthorn (Rhamnus cathartica) was first brought to Minnesota from Europe in the mid-1800s and quickly became a popular hedge plant. This tall shrub quickly busted out of its landscaped environments to invade forests and other natural areas.

Though commercial nurseries stopped selling the plant soon after its arrival in North America, it had already gained a significant foothold. Tenacious buckthorn hedges may still be found in older neighborhoods.

The plant has no insect predators and is immune to native diseases.  Birds and bees and other animals eat buckthorn seeds, but at their peril: the seeds can have a severe laxative effect in some animals, a condition that is often fatal in smaller birds.

amur mapleAmur maple (Acer ginnala) is a small tree, growing up to 20 feet high, which is sometimes pruned into a hedge. A native of China and Japan with fragrant spring flowers and bright red fall foliage, it was introduced to North America in the 1860s as an ornamental. However, its prolific seed production has caused it to become a highly invasive threat to native plants in natural areas in the northern U.S.

Though it is still being sold commercially as an ornamental, amur maple was designated as a “specially regulated plant” by the Minnesota Department of agriculture in 2016, advising it be planted only in mowed and maintained landscapes situated at least 100 yards from natural areas.

honeysuckleHoneysuckle (specifically, the non-native bush varieties: Lonicera tatarica, L. morrowii, L. x bella, L. maackii) are upright deciduous shrubs that grow 5 -12 feet high. These non-native cultivars were introduced in North America as ornamental shrubs that were good for wildlife, and commercial nurseries continue to propagate them.

But despite their pleasant look and fragrance, they are bad neighbors: they overwhelm native shrubs and plants, shade out herbaceous ground cover, and deplete soil moisture.

white mullberryWhite Mulberry (Morus alba) bears fruit that is a favorite food of silkworms. The tree was brought to North America from China in the 19th century with the goal of boosting the continent’s fledgling silk industry.

The process proved costly, and the idea was abandoned. But not before the white mulberry had sprung up throughout the U.S. This fast-growing weed tree grows up to three feet each year, and can grow up to 50 feet high. It is a particular threat to the native red mulberry (Morus rubra) through hybridization and the transmission of a harmful root disease.

barberryJapanese barberry (Berberis thunbergii) is a medium-sized woody shrub introduced in North America in the 1870s as an ornamental. It quickly escaped its confines to threaten native species in woodlands and natural areas. Its multitude of small twigs and branches forms dense, thorny thickets that crowd out native trees and herbaceous plants.  Its red fruits can hang on into the winter months, eaten by birds and other animals who then disperse the seeds as they move.

The Japanese barberry’s long-lasting leaf density increases ground level cover and humidity, creating an hospitable habitat for whitefooted mice and black-legged ticks, which increases the risk for Lyme and other tick-borne diseases. Japanese barberry’s dense thorny thickets also prevent the movement of wild and domesticated animals and people in the wooded areas.

knowtweedJapanese Knotweed (Polygonum cuspidatum) is a shrub-like plant that can grow over 10 feet tall. It was introduced to the U.S. from Japan in the late 1800s for ornamental purposes and erosion control. Its rhizomes — stem-like structures that grow horizontally across the soil surface from which new roots and shoots form — allow the plant to spread quickly. The resulting dense thickets suppress the growth of native vegetation around it. Japanese knotweed colonizes rapidly in floodplains, riverbanks, and wetland areas, though it can survive in full shade, high temperatures, high salinity and drought.

Removal and Control

Returning a property overrun by invasives to its natural state doesn’t happen overnight. It takes expertise and upkeep to bring back native species and ensure that they flourish. However, the result is a property that is a productive part of our delicate ecosystem.

Our program has three ecologically sound steps:

Identify– We’ll scout your property to break down the mix of native and invasive plants and formulate a strategy

Remove– Next, we’ll perform an initial cutting and removal of invasive plants within the property bounds. Depending on the situation, we may also use an herbicide to discourage particularly tenacious invasives.

Repeat – A single removal isn’t enough to stamp out invasive plants on your property for good. Native species need time to establish themselves. To give them the best possible chance, we return for between 2-5 years to repeat the process.

Let SavATree be your partner in fighting invasive species. To learn more about our action plan, get in touch.