It seems each time I talk about raingardens, someone has to ask about vermin. You know, squirrels without the cute fuzzy tails: rats and mice. The question is usually, "Do raingardens bring in vermin?". My standard answer is, "No". But after hearing it so many times, I decided to get some additional advice on the topic.
I talked with both a horticulturist and a biologist about this question. On my list were Jay Ross, Horticulture Curator at the Tulsa Zoo, and Stephanie Rainwater, a biologist at URS. Jay and Stephanie both noted that any garden with dense vegetation can provide a nesting area for all types of critters, from songbirds to cats to, you know. The key to what critters you attract is what food supply is nearby. If you have insects, you should get birds that eat insects, and so on.
In the public arena, a community might consider whether the garden is located near areas of animal feeding (advised or not), such as a duck pond or petting zoo. Likewise the residential homeowner should consider whether they leave dog, cat, or bird food where other animals can access it. In my own yard, I've found the compost heap to be a problem.
But are there features that make raingardens uniquely less prone to being used by vermin than other landscaping? The answer is yes. Raingardens are designed to flood - every time it rains. There aren't a lot of critters that will put up with being flooded on a regular basis - they'll pick somewhere else to nest.
So, what does all this mean? Raingardens should be less likely to house these unwanted guests than other types of gardens and landscaping, a fact that should encourage others to bring stormwater controls into their landscaping.
