7 Invasive Non-Native Trees in Wisconsin

Invasive trees pose a problem for Wisconsin. What are some of the most common non-native trees?

Invasive trees can invade the land, outcompete native species, and devastate ecosystems. Most of these trees are capable of reproducing and spreading at extraordinarily fast rates.

It’s helpful to know which trees are considered invasive so that you can avoid including them in your landscape. Let’s look at 7 invasive trees found in Wisconsin.

1. Norway Maple 

The Norway maple is an invasive tree that produces many seeds that germinate and proliferate quickly at the expense of native plants that are usually less tolerant of shade. 

Outside of its native habitat, this tree can thrive in a range of conditions, but it can alter the biodiversity and structure of woodlands if planted there.

norway maple tree with growing big leaves

2. Tree of Heaven 

This small, rapidly growing tree can reach heights of 70 – 80 feet and can grow as wide as 6 feet across. It has smooth stems, pale gray bark, and light brown twigs.

Large clusters of yellow flowers emerge among its leaves in early summer. Its flowers are unique in that they emit a strong aroma reminiscent of rancid peanuts.

This tree actively invades almost every area around it. It also releases chemicals that are detrimental to surrounding vegetation and wildlife.

tall tree with thin trunk

3. Russian Olive 

Russian olive trees were initially planted as ornamental trees. It can grow to be up to 35 feet tall when mature. 

Russian olive trees can have dark, prickly branches hiding within their leaves. 

old russian olive tree in the forest

4. White Mulberry 

White mulberry trees are native to Asia and were brought to the United States to serve as food for silkworms. This fast-growing deciduous tree can grow 30 – 50 feet tall. 

White mulberry leaves are glossy. The bark of younger trees is orangish-brown; its color grows richer as it matures. 

This tree can tolerate a variety of environmental factors, including wind, drought, and salt. 

Be mindful when planting white mulberry; it can overrun native trees, including native mulberry trees. 

white mulberry in the garden

5. Scots Pine 

Scots pine is a coniferous tree that can grow 70 – 120 feet tall and 3 – 5 feet wide. These trees grow in isolated areas throughout Wisconsin. 

Young scots pine trees have glossy, silvery gray bark that becomes reddish-brown and more textured as they age.

These trees grow quickly in their early years and their roots often crowd out other plants’ roots. Although they’re not incredibly destructive, scots pines can easily invade surrounding grounds if not monitored and maintained. 

6. White Poplar 

White poplar trees are fast-growing trees that are often used to restore wooded areas due to their salt and drought tolerance. A mature white poplar tree can reach heights of 40 – 70 feet.

While the tree’s canopy is typically broad, it can be trimmed into a narrower column or pyramidal shape. 

White poplar trees are unique in that their leaves have a dense wool-like coating on their undersides. 

These trees can occasionally spread to surrounding areas where other plants and trees grow. 

white poplar tree trunks in the forest

7. Common Buckthorn 

The common buckthorn is a hardy tree. Its leaves develop early in the year, and they remain on the tree’s branches until the end of the season. The leaves, which are simple and finely serrated, grow in an alternate pattern along the branches.

This tree produces an abundance of fruit once it matures, which passing birds consume. It also casts deep shade on the ground below, which can stifle the growth of shorter plants and tree seedlings.

black buckthorn berries in the forest
Leila Haynes
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