Good question, quite a lot.
A healthy understory is very important in that it provides habitat essential for a wide variety of creatures. The understory includes, smaller trees, shrubs, thicket, perennials, grasses, and the smaller vegetation layers of moss and lichen.
So what’s in the thicket? Well, an awful lot of birds. In this post, I will show you how birds use dense vegetation. The post is more about the bird’s habitat than it is the birds themselves.
It is not so much that the berry, seed and nut producers are providing necessary and nourishing food (which they are) but more importantly the mass of crisscross twigs provide safety and shelter. This is what most gardeners forget about. They are conscious of the food-producing plants, but many times don’t provide the shelter plants in any number if at all.
The wicked winter this year is trying on birds and staying out of the winter winds and hungry predator’s claws is of utmost importance. These are two reasons birds make gardens a home. With another foot of snow this past week, the winter rages on right into Spring. Leafy plants are later to bud, yet migrating birds are on their way back. They need conditions to keep them safe and provide needed sustenance. So look for them tucked deep in your thickets.
With the exception of rain forests, the understory has a greater diversity of species compared to the canopy layer. The understory plants provide shelter and a rich food source to many beneficial insects along with small mammals, amphibians and birds.
The understory plays its role in maintaining the landscape by protecting the resources of water and soil. Plants, alive and those reduced to leaf litter, help prevent surface runoff, sustaining a healthy ground layer with a deep layer of good topsoil. Runoff takes with it the soil and organic matter, causing erosion, siltation of waterways and of course, decline in soil productivity. To read on creating this layer see, Leaf Mold Magic.
While most gardens cannot have a true forest understory, they can have the next best thing. Preserve any understory that remains on a property and plant in a way that mimics a natural understory, understanding that what one plants is never going to be natural in the same way it happens in wild nature.
In this type of landscaping, having typical garden cultivars of popular perennials is not the real goal. Wild species evaluated for garden use having similar competitive value are those typically used. We want the robust nature of these plants, but we also want them to create harmonious schemes. This is where this type of landscaping makes it more difficult to achieve for a typical gardener.
We want the experience of meadows, prairies, open fields and forests in our urban environments, but that just is not going to happen by what I mention in other posts. The space allocated to any of these environments created likely will not be sufficient.
We do what we can though. Sometimes just letting the perennials stand through winter adds shelter and food, but it also adds visual interest. Having a garden adjacent to woods is really a boon for wildlife. Planting a few native shrubs helps them as well.
Walking into the woods, one may not notice the understory shrubs as they blend seamlessly with the forest canvas. Part of the reason is that many are just seedlings and saplings of the canopy trees making it more difficult to differentiate what is actually there in all this growth. But, the shrubby layer and density is disappearing from forests around the country. Why?
The shrubs and thicket are a detriment to forest timber cutting and are often cleared. These plants are the ones adapted to growing in the shade, the herbaceous layer which includes all non-woody plants including annuals, perennials, grasses and sedges. Many of our forests are losing this precious and varied understory.
So how does this relate to conscientious landscape design?
It actually creates a more visually interesting landscape with interesting features as logs, stumps and standing perennials if taking cues from nature. I have three logs I incorporate in my own landscaping. Being a small city garden, I can not have fallen and dead trees, nor can I have a brush pile that you might find in a natural setting.
In the schematic above, you can see how the property is heavily planted, with numerous trees, and shrubs. The ground plane is densely planted with grasses and perennials. Grouping of plants benefit wildlife. Also many are food sources. I employ the benefit of fruiting plants and have many shelter plants, deciduous and numerous conifers. It saves money on fertilizer and water use. The leaf layer mitigates erosion of topsoil. Here I mulch the fallen leaves and use them as compost. Plants stay warm in winter and by Spring the leaves nourish new growth. Get and give, the way nature works.
Layers from this varied planting in the landscape intercept more water, preventing it from entering the storm sewers. I water my garden very little and only in long drought seasons. I don’t do it to save the plants, but to have the plants make food for the wildlife. My small garden has five trees and more shrubs (some as large as trees) than I even ever counted, all responsible for the wide variety of birds and insects you see in my garden on this blog. The wildlife means more to me than the plants. I can make new plants!
The key is variety and density. No, I could never have a forest here, but how I treat the ground layer makes a nod to the way one works. Taking clues from nature makes for responsible gardening.
See the first two posts of this series on Conservation Landscaping for more information.