One of the big lessons I have learned in the garden is how to create layers. It is important not only because it makes the garden more interesting but also because it encourages a more natural habitat for birds, insects and animals in the garden. Here in my Northwest garden I have about 6 different layers, the tall trees, understory trees, large shrubs, small shrubs, perennials and ground covers.
The layer I liked to concentrate on when I was building my garden was the understory trees. This layer of the canopy consists of trees that range in size from 20 to 40 feet. The native trees that are in my garden are Doug Firs, Pseudotsuga menzeisii, Western Red Cedar, Thuya plicata, and Big Leaf Maples, Acer macrophyllum. The large conifers are more than 100 feet tall and the Maple is around 60 feet tall. This creates a tall overhead canopy but leaves a lot of space between the big trees and the ground.
I had spent more than a dozen years working at the Miller Botanical Garden in Seattle and it was known as one of the best woodland gardens around. Mrs. Miller, the original owner and gardener, had tried to add a lot of fall interest to the garden because that was her favorite season. One way she did that was by adding trees with good fall color. This gave me the opportunity to see several great trees grown well in a similar environment.
In my garden I cleared about a dozen Big Leaf Maple seedlings which would have made the garden very shady. The Big Leaf Maples are a short lived tree while still getting very tall. My thought was that I would create this in-between layer of trees to enhance the taller canopy. This in-between area also provided a habitat for the birds, Many of the trees I considered grew naturally at the edge of the woods of taller trees so could tolerate part shade. That made them ideal for growing amongst the Doug Firs.
Being a plant collector I also saw this as an opportunity to add a number of different types of trees to the garden. This is a luxury that I never had in my city garden. On a smaller lot that already had nice trees, new trees were out of the question. I surveyed the garden and came up with a number of candidates to fill this special niche. Next week I will talk about the specific trees I added. Until then think of what you would like to add to your garden if you had the opportunity to add several trees.