Finding the optimal diversity of plant species will encourage more wildlife, including beneficial insects.
Native plants offer the gardener an overwhelming array of benefits, but they are not without controversy. Despite all the evidence that landscaping with more native plants is healthier for people and for wildlife, some gardeners seem intent on attacking the whole notion.
Mention the concept of “biodiversity“, on the other hand, and you will find nearly uniform support. Biodiversity is so obviously a good thing – like Mom and apple pie – that no one could possibly be opposed to it. Right?
While biodiversity can be a (very) good thing, like any good thing too much of it can be bad.
For example, when we introduce a new invasive plant to a forest we are (temporarily) increasing the biodiversity of that forest: more species exist in the forest than did before, but this is clearly not a good thing.
Large groupings of host plants, like milkweed, are more likely to attract and support bees and butterflies.
Too much of a good thing can also be a problem, even in a native plant landscape. Attempting to plant too many different kinds of native plants in your garden or landscape can often be counterproductive, and here is why: over-diversification.
No matter where you live, there are probably many thousands of species of plants that are native to your county or state. Hike a mile or two through a nearby wild forest or prairie and you will likely spot hundreds of species of native plants.
But few gardeners own yards the size of a state, county, forest, or prairie. Most gardens are measured in the hundreds, maybe thousands, of square feet instead. And for the native plant enthusiasts tending these smaller parcels trying to squeeze in hundreds or thousands – or even dozens – of different species of native plants can be a mistake.
Every type of wildlife has certain habitat needs. This can be a type of ground cover, or a certain plant. Wildlife will use their senses, like smell or sight, to locate these habitat needs and if you dilute them too much in your landscape you run the risk of failing to support the insects or birds you intend to attract.
A study of gardens in England published in 2007 concluded, in part: “Entire gardens, or large parts thereof, given over to individual land-cover types, with different gardens providing coverage of different types, would be ecologically more valuable.”
In other words, it is ideal if each gardener treats their own garden as a single type of community because the network of different gardeners (with different community types) throughout a city or town provides the right amount and scale of diversity.
Planting three purple milkweed plants in a garden might attract some Monarch butterflies, but planting three dozen of them is much more likely to do so. Planting one or two turtlehead plants might attract a Baltimore checkerspot butterfly, but planting a hundred square feet of turtlehead is much more likely to be an attractant.
Large groupings of plants are attractive to people and to wildlife.
It may seem unnatural to entertain the idea of planting fewer species of native plants, but it makes sense once you think it through. An acre of prairie might contain 75 to 100 different species of native plants, but any given square foot within that acre might contain just six or eight species. We are still aiming for biodiversity, but now we are paying attention to the scale at which that biodiversity exists.
If you are gardening in a small area (hundreds or thousands of square feet) there is only so much variety you can offer to wildlife before you become self-defeating. In a four hundred square-foot garden, you should not aim to be all things to all animals: the haphazard plant shopping model (“three of these”, five of those, one of that”) just won’t cut it if your goal is to have your yard function at its ecological optimum.
Here are three steps to optimize your biodiversity:
- Decide your habitat type. Don’t try to cram canopy trees and an urban meadow both onto a small residential lot: pick your habitat type, then stick to it.
- Pick your plant palette. Chose a handful (maybe a dozen, no more) of plants that are locally native and that are well-suited to your soil type, shade conditions, etc.
- Plant a lot of plants. Remember the prairie example I mentioned earlier? It had six to eight plants per square foot, so don’t be afraid to plant your native plants densely. No more leaving 18 or 24 inches between plants in a wildlife garden!
Don’t be afraid that by specializing in a particular type of habitat, or that strongly emphasizing only a few species of plants, that your garden will be boring. As far as wildlife are concerned, nothing could be more appealing.
© 2012, Vincent Vizachero. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. If you are reading this at another site, please report that to us
