Green is good, right? Unfortunately, it's not that simple. Some exotic species - those that have come to Penn's Woods from other geographic areas - become invasive, meaning that they invade, degrade or otherwise disrupt the long-occurring balance of an indigenous natural situation. Many unique challenges are presented by these alien invaders.

The prevailing perception that all green is good is the first challenge. Widespread education on the issue is desperately needed. The good news is that anyone can help spread the word, not the weed.

Another obstacle is that unlike some other forms of environmental degradation, the problem is caused by dynamic, adaptable living organisms that are capable of vast spread through reproduction and distribution by wind, water, roadways and many other mechanisms. Most distribution by humans is inadvertent, such as when reproductive material hitches a ride on hiking boots, watercraft, and vehicles. However, some introductions of exotics are intentionally spread for a specific use by humans.

Accurate identification of problem species and areas to prioritize for control are difficult. Without any plant identification training, anyone can start the search for invasive plants by looking for vast monocultures, or large widespread populations of one species of plant existing in an area. The stand could simply be an aggressive native species, but more likely, the size of the grouping could indicate the presence of an invasive species. Some species that form these vast monocultures include Japanese knotweed (Fallopia japonica), multiflora rose (Rosa multiflora), autumn olive (Elaeagnus umbellata), and honeysuckles (Lonicera spp.). The largest impact of large populations of invasive plants is the displacement of biodiversity, the right community mixture of species that serves different ecological functions.

The converse challenge to the existence of vast, easily recognizable populations is the presence of discreet invasions of species that are fit for invasion and spread. Upon introduction, populations of invasive species are initially small and unassuming, preventing early detection by the untrained eye. Therefore, a need exists for education, training and technical assistance in identification of potentially harmful species. For excellent identification resources, go to National Invasive Species Information Center.

Another challenge confronting the battle with invasive species is a misconception surrounding the definition of the problem. Not all introduced exotic species become invasive, in fact, only 1-5% invade. But when considering how many species have been introduced, the total number of problems is considerable, so a principle of precaution should be applied.

A final challenge on the invasive plant front is the controversy, frequent mis-use and complexity surrounding the use of chemical herbicides to treat plant infestations. Here, more research, education and precaution should be the guiding principles.

The key to effectively combating this complex problem and eventually winning the war is education! The more that good information can be spread throughout the human population, the more likely we are to gain an acceptable level of control within our natural systems, our backyards, and our outdoor community assets. A lot of good information is starting to become readily available to a wider audience, but much more work needs to be done. Everyone should know that each individual has the power to effectively wage local battles against invaders by taking some simple, yet effective preventative steps, which include:

• Go native with plant purchases. This includes familiarizing yourself with plants native to PA and even those native to your local area. Ask questions at nurseries related to scientific names, propagation methods, and whether the plant is a pure native or a cultivar. If you're not sure it's a pure native, don't buy it and then let the nursery owner know why you're not buying.

Some invasive species still propagated and sold in Pennsylvania include: Norway maple (Acer platanoides); burning bush (Euonymus alata), butterfly bush (Buddleja species), Bradford pear (Pyrus calleryana 'Bradford'), Chinese and Japanese wisterias (Wisteria sinensis, W. floribunda), English ivy (Hedera helix L.), Oriental bittersweet (Celastrus orbiculatus), common privet (Ligustrum vulgare), Japanese spiraea (Spiraea japonica), Japanese barberry (Berberis thunbergii), porcelainberry (Ampelopsis brevipedunculata), Japanese honeysuckle (Lonicera japonica), and exotic bush honeysuckles (Lonicera: L. maackii, L. morrowii, L. tatarica, L. standishii).

You may be thinking, "Wow, what can I plant?" Native alternatives to these and other invasive species exist and can fill the same niches as their invasive counterparts. For example, Virginia sweetspire (Itea virginica) can serve as a bright autumn red colored alternative to burning bush in some areas. When searching for native alternatives to any of these alien invaders, consider the source of information. What is native in Colorado is probably not appropriate for Pennsylvania. Also consider your elevation, soil conditions, moisture, and sunlight levels when choosing any plant.

• Educate yourself on the invasive species that could be residing your property. Identify problems and ask for help from your local authority on invasive species, such as a non-profit, conservation district, Penn State Extension, or the PA Department of Agriculture.

• When working or recreating in the outdoors, clean boots, boats, and equipment before moving to other areas to prevent further spread of any invasive plants.

• Volunteer for local weed whacking events, native plantings, and related conservation activities in your area.

Although this problem can feel overwhelming, the war against alien invaders can be won through knowledge, vigilance, cooperation, and informed action. Remember, educate yourself and others around you. Inspire local action and seek assistance from the experts to ensure that your battle plan is sound.

Some quality web resources from which to collect good information on invasive species include:

• National Invasive Species Information Center
• Exotic Forest Pest Information System for North America
• Mid-Atlantic Exotic Pest Plant Council
• National Park Service's Weeds Gone Wild
• National Wildlife Federation
• Penn State Cooperative Extension Weed Management
• PA Department of Agriculture
• PA Department of Conservation and Natural Resources (DCNR)
• DCNR Invasive Exotic Plant Tutorial
• PA Native Plant Society
• The Nature Conservancy: The Global Invasive Species Initiative
• USDA Animal and Plant Health Inspection Service
• Western PA Conservancy

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