A greener shade of “green”

Jun. 08, 2013 @ 10:31 AM

Spending time outside tending your landscape is a satisfying way to improve our health and that of our surroundings. However, when water, fertilizer and pesticide use gets factored in, how environmentally friendly is our yard?   Well, it turns out that, by applying some basic principles you can reduce the need for these inputs, and yards can become shady “green” oases which pay off in unexpected ways. 

When it comes to sustainability, not all landscapes are created equal. A healthy and diverse yard contains several “layers.” At ground level there is soil, mulch, and ground-cover. The mid-level contains herbaceous and shrub layers. Above head-height, there are canopy and understory trees. This “layering” makes for an interesting, diverse and healthy yard-ecosystem. 

The point is not to simply fill space with vegetation, but to create a diversity of habitats that provide niches for microbes, insects, birds and other animals.

Consider the traditional “mow-and-blow” yard with a foundation planting of shrubs, an expanse of lawn and maybe a tree or two near the edge of the property. What sorts of habitats are available in this setting for predatory insects? Those shrubs likely have a buffet of tasty aphids, mites, miners and scales, but any predator arriving at the feast won’t stay long without conditions favorable to its own life-cycle.

Without natural predators, the solution to the problem most often comes in a bottle, which in turn reduces biodiversity by killing off insects indiscriminately (the harmful and the beneficial). The idea that chemical use can be reduced in functionally diverse landscapes isn’t new. It’s part of a broader concept known as “integrated pest management”, which is slowly catching on as the unintended consequences of pesticide use become more obvious and consumers demand safer alternatives.

Starting from the ground up, healthy soil is full of living organisms and is the keystone to healthy plants. Improvements will have long-term benefits and are easy to achieve by increasing organic content through compost and organic mulch applications. They increase water infiltration, holding and availability rates, while improving drainage, pore space and rooting depth potential. They also boost nutrient availability and general soil health, ultimately reducing or eliminating the need for fertilizer. 

Be careful not to over-do the mulch. Initial layering can go as deep as three inches, but subsequent applications shouldn’t exceed an inch or two. Once a good layer is established, simply refreshing and raking the surface can dress up a bed without burying your plants. 

Another practice we can change is the mis-application of water. As we nervously approach our hot and dry season, I’m reminded of the annual spring migration of plants from the garden centers to our yards. Where did they go?  Chances are the locations selected for these plants had more to do with their height, flower and leaf color, or where a blank space existed. Well, here’s another consideration…how much water do they need? 

Different plants have different moisture and drainage requirements. Plants placed next to each other should have similar needs. Otherwise, you often maintain one plant at the expense of the other. This grouping concept is called “waterwise” landscape design. There’s lots of information available on this subject, especially from N.C. State Cooperative Extension and Durham’s City/County Planning and Water Management Departments. 

Once you get up into the tree layer of the canopy, there are some practices which are more sustainable than others.  For example: Never top your trees (and yes, crepe myrtles are trees). Don’t use spikes to access trees for pruning purposes. Do try to match your tree to your site to avoid costly consequences later and, finally, look for native selections when shopping for new trees for your yard.

Alex Johnson is Alex Johnson, urban forestry manager for the City of Durham.