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In The Country

How to Prevent an Alien Invasion: The Amateurís Guide

Tim Iverson
Seasonal Naturalist
Cunningham Falls State Park

(3/2014) Soon the seasons will begin to change, and the weather will become more favorable. Warmer weather and spring showers will cause the plants to bloom. For those of us with a green thumb this is the time of year when we start planning our gardens. Most of us choose what to put in our gardens based on popular trends, appearance, and ease of care. While these are important factors when choosing flowers or plants there are more important factors to consider when selecting what or what not to plant. Before purchasing and planting you should be asking yourself one thing before everything else: Is it native?

The importance of selecting native plants over non-native plants is paramount. Non-native, or exotic, plants often become invasive species. Now you might be getting confused by throwing all these terms around, so Iíll attempt to clarify. Native species are plants, animals, or any organism found in an ecosystem that is supposed to be there. Exotic or non-native species are any plants, animals, or organisms that are found in a given ecosystem that are not supposed to be there. For instance, Iím sure by now youíre familiar with those pesky little brown stink bugs that can be found literally everywhere in our area these days. Prior to about 2008 you couldnít find them in Maryland. They werenít even documented to be in the United States prior to 1998. With this example we can clearly identify that these Brown Marmorated Stink Bugs are exotic or non-native. They originally hail from Japan, and are most certainly not supposed to be here. As a result of their introduction and rapid expansion they are now considered invasive.

For a species to be invasive it must aggressively invade and establish itself in an ecosystem at the expense of other species. Invasive species thrive while others suffer. Invasive arenít necessarily always exotic. Even natives can be considered invasive, certain kinds of weeds for example. The problem with invasive species is that they can cause ecological and/or economic damage on a large scale. When dealing with non-native species they can quickly become invasive because they have been pulled out of their natural ecosystem where natural checks and balances like predators or diseases can help keep population numbers in check. When those bars are removed damage caused by these species can be dramatic. In order to help curb this issue we can combat it before it even becomes a problem.

There are many natural advantages to planting native species over exotic ones. For starters because they are native they will generally be much easier to care for. They evolved to live right here for these exact conditions, and will require little attention. Theyíve spent thousands of years figuring out how to best survive right here, and are uniquely capable of flourishing on their own. They can handle variable weather conditions, and outside of drought conditions should not need to be watered. Natives are heartier and can last for two to four seasons depending on the species allowing for longer enjoyment. Native plants usually donít require the use of pesticides or fertilizers either. Birds, bugs, and other wildlife have all developed a relationship and dependence on native plants.

Native flowers, trees, shrubs, and other plants all provide valuable food and habitat for our local wildlife. By planting things they recognize and depend on you can help cultivate a thriving habitat to observe nature up close and personal. You can even try to cater to the wildlife you wish to see. If you want to see specific birds or butterflies do a little research to find out the types of native plants they like best. If you can plant what they like you will be more likely to attract those species. For example, in the spring and fall many birds will seek out insects hiding in the leaves and bark of oak trees or poplars. Once the summer has set in they switch their diet to fruits and berries. Monarch Butterflies rely almost solely on Milkweed for nutrition during reproduction and migration times. Itís all about catering to the needs of the animals or insects you would like most to see. Do a quick internet search to identify the types of habitat and food that a specific species will need.

Any experienced or novice gardener should know there are other important factors to consider ensuring you have a successful garden. Once youíve selected the type of flower, shrub, tree, or plant you wish to plant consider where and how you place it. Light conditions are very, very, very important. A shade loving plant will just not survive in the hot summer sun, so pay close attention to the location you place your plants for their specific needs. Also, consider the proximity the plant is with other surrounding plants. You want to ensure that when they all reach full growth maturity they will have plenty of room. While densely packed plants may help prevent the growth of weeds, it will also hinder the growth of some or all of your new plants too! Lastly, be sure to know when the best time to plant your new plant is. Generally, after the last frost of the spring season is likely to occur is a good time to begin that endeavor.

By planting only native species you will be doing your part to significantly reduce the chances of and prevent the spread of exotic or invasive species. Many of the invasive plant species in the southern United States were originally introduced and used for gardening and landscaping purposes. Continuing to introduce exotic species into local areas will only further the spread of newer invasive species. Valuable habitat is lost daily to development. By planting only native plants you can provide wildlife an oasis with necessary food and shelter.

To learn more about local native plants visit the Maryland Native Plant Society at or the Pennsylvania Native Plant Society at

Read other articles by Ranger Tim Iverson