In my previous forest gardening posts, I discussed in some detail the many different layers of a forest garden, and gave lots of examples of plants that could be included in each layer. Click here to find all my forest gardening posts. But there are other considerations, as you will read:
Not Just Layers
What makes a forest garden is not just architecture of the layers. There are other aspects that make up a forest garden. For example, vegetation patterns and density should be considered. In designing your forest garden, you will probably want to strive for a "lumpy" texture. In other words, create a lot of variation in how the plants are arranged and especially in the density of the plantings. Scientific research has shown that areas with great variation in plant density are more attractive to bird and insect species, thus increasing your forest gardens biodiversity (a very good thing). It also helps to promote a better balance between harmful and beneficial insects.
Plant diversity is also important. One of the chief differences between a traditional orchard and a forest garden is that orchards primarily feature a single species laid out in neat rows. A forest garden has a much greater diversity, and is not nearly as orderly. In designing your forest garden, you will want to pack as much diversity into your site as possible given the area you have to work with.
In addition to the physical structure of your forest garden, you will want to pay attention to its social structure. Your forest garden will be made up of the trees and other plants you intentionally include. But it will also be made up of trees and plants already present or that show up later as volunteers. Insects, spiders, centipedes, millipedes, birds, reptiles and small mammals will also take up residence. If you are lucky enough to have acres of forest garden, you might also get large mammals. All this biodiversity will interact with each other. This interaction - the food chain, pollination, decomposition, predator/prey relationships, symbiotic relationships, parasitism and so forth - is the social structure. Some thought should be given to that social structure.
For example, if you want to have a healthy population of pollinators (and you should want that), then you will need to plant a variety of flowering plants to attract them. By variety, I am talking about various sizes, shapes and colors of the blooms, as well as a variety of bloom times through the year. If all your plants bloom during only one part of the year, this will be a very inconsistent food source for the pollinators and will discourage a healthy population from forming.
You might also want to allow for some dead wood, such as dead branches and fallen tree trunks, to be a part of your forest garden. This dead wood will be used as food, nesting sites and protective cover for a variety of insects, birds and other animals, as well as fungi.
Much of the sun's energy captured by the forest garden will eventually turn to rot. This will improve the soil, but we can also capture some of this energy for our own use by growing edible and medicinal mushrooms, many of which actually prefer damp and shady conditions.
Soil structure is another aspect of your forest garden you should give a thought towards. There is a great deal more going on under your forest garden than just those tubers you planted. The roots of all trees, shrubs and plants are down there. Some are deep, some shallow; some will spread out greatly and some won't. Many fruit trees, such as apples and pears, have fairly shallow root systems. Many nut trees, such as pecans and hickories, have very deep taproots.
Within the soil, many small mammals, insects, worms, fungi and microbes live, eat and die. They too will have an effect on soil structure. Some of these organisms will decompose plant matter turning it into nutrient rich soil. Others, such as burrowing animals like moles and voles, will aerate the soil, and will carry the nutrient rich topsoil deeper into the ground.
Another aspect of the forest garden that should be taken into account is succession. The trees and other plants you include in your forest garden will grow up over time, and eventually die (I've already mentioned that it is a good idea to leave some dead wood in the forest garden). New trees and plants will take their place. You might need to prepare yourself for the dynamic and constantly changing nature of your forest garden. People like to control nature, but you cannot control your forest garden. At best, you can only hope to guide it.
It is common today for many people to look on well-manicured lawns and very neat & orderly gardens as highly desirable. But a forest is anything but well-manicured, neat and orderly. Your forest garden shouldn't be either.