Invasive or Non-Invasive? What Not to Plant in Your Garden

Just because a plant is nonnative doesn't mean it's bad.

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Invasive plants can pose a problem for gardeners and for wider ecosystems. As a garden designer, I always begin any planting scheme with a clear idea of the native plants of the area and take care to avoid the use of any invasive species which may become an issue for the region in question. 

But as I have undertaken my work, I have noted that there are a number of misconceptions about what the term "invasive" really means. Furthermore, people are not always clear that what is invasive in one area will not be a problem at all in another. Plants that spread easily are not necessarily always a problem; and invasiveness, like so many other things in gardening, is extremely location-specific. 

What Are Invasive Plants?

When we talk about invasive plants, we must distinguish between native plants which can proliferate quickly and become "weedy" in a garden, and nonnative invasive species. 

Some people may be concerned about plants which spread easily, which can be challenging to control. Such plants may be extremely vigorous, self-seed readily, or spread prolifically through their root systems or across the ground. Some native plants, however, can have these characteristics and not be a problem. In fact, some native plants which thrive in your garden and spread readily are beneficial.

These may be a boon in creating ground cover, protecting the soil, and enhancing the garden for wildlife. Plants sometimes bemoaned as "invasive" weeds may actually just be so successful because they are the right plants for the right places. They can be helpful in some instances in aiding the establishment of a garden ecosystem and in creating lower-maintenance designs. 

The latter category of nonnative invasive species is far more damaging, as plants within it can have a detrimental effect on ecology in a bioregion. They might outcompete native species, impacting biodiversity and taking a toll on local wildlife. They also come at an economic cost, as authorities and governments seek to control the problems.

It is important to note, however, that what is invasive in one region may not pose a threat at all elsewhere. In some very specific scenarios, even a nonnative plant may prove very useful in a garden. Understanding how that plant proliferates and looking at how it is used (and where necessary controlled) is key. 

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Gaining Plant Knowledge

The first step in recognizing which plants we should avoid is developing an understanding of the plants which are native to our areas. We can build our knowledge in this by looking at books and online resources, and consulting with experienced botanists and gardeners where we live. 

A good garden design should always have a high proportion of native plants. Native plants have evolved alongside the wildlife and people of a region and are best adapted to the climate and situation where you live. They fit into specific ecosystem niches and help you create a garden that is kind to people and planet, and which really will stand the test of time. Native plants can often be the best plants for place. They provide for your needs and create beautiful and abundant spaces. 

It is important to note, however, that gardeners sometimes gain by considering nonnative species to fulfill specific functions and provide specific things. After all, many of the common culinary crops we grow are not strictly native to where we live, but have been cultivated over many years to provide us with the yields we require and desire. And even nonnative invasive species have occasionally been shown to be beneficial in enabling the restoration of degraded land and in conservation schemes

So, while native plants should always be the backbone of any garden, utilizing solely locally native plants may be needlessly restrictive. There could be some very specific times when a plant not native to your specific location is the best choice—as long as it is not a problematic invasive in your area.

Nonnative plants which pose a threat to indigenous species and ecosystems should absolutely be avoided and not planted in your garden. And native planting should always dominate any design.

But it is important to remember that nonnative plants which thrive where you live will not always be problematic invasive plants in your area, and so it is important to do careful research when deciding what to grow, and what not to grow, in your garden.