Written by davethetreecenters • April 30 Understanding Shade in the Garden
When choosing plants for the garden, the words shade-tolerant, or grows in shade are regularly seen. The true situation with shade is a little more complicated than that, and a better understanding of the various kinds of shade found in gardens is helpful in making good choices, and avoiding costly failures. Let’s think about the different kinds of shade, and their impacts on the growth of plants.
The Different Kinds of Garden Shade
- Shade from Buildings – supports a wide range of plants
- Shade from Deciduous Trees – easier place to grow many plants
- Shade from Evergreens – too dense and permanent for most plants
- Deep, Dry Shade – hard for almost all plants to survive in
Shade from Buildings
This kind of shade is the most forgiving, and the easiest to find plants for. A wide range of plants will grow well in areas shaded for all or part of the day by a shadow from a house or taller building. The primary reason for this is that the sky overhead is not obstructed, so plants still receive a full spectrum of light, containing all the wavelengths needed for growth. The only difference is that the light is less intense, so some plants will grow more slowly, or with more open growth and fewer leaves, as they adapt themselves to the lower light levels.
When looking at the areas in your garden that are shaded by buildings, it is important to look at the right time of year. The critical periods for most plants are equinox to equinox – March 21 to September 21. This is the growing and flowering season, and shade when they are dormant, and probably with no leaves, is not very important. As the year progresses to the mid-summer solstice, the sun rises higher in the sky each day. The length of a shadow at noon becomes shorter and shorter. So if you can, notice where the shade reaches to around one or other of those dates – it will be the same for both. Anywhere inside that area should be considered partially-shaded, although in June some of it will be in full-sun. Any plant that needs sun or partial shade will thrive in that zone.
Shade from Deciduous Trees
For many gardeners, these areas have a lot to offer, particularly in the trees are mature, with high branches, and spaced widely apart. Although you will need to do some good soil preparation, and attend to watering in the summer, with that done you can grow a wide range of shade-loving plants. From Japanese maples to camellias, and including all the different rhododendrons and azaleas, many shrubs and smaller trees that naturally grow beneath larger trees will love this area. Because the big trees leaf-out a little later, there is a sunny window of opportunity for short-lived spring plants, and early-blooming shrubs, to flower and grow before the full shade of summer arrives.
The shade from deciduous trees has been filtered – some of the wavelengths needed for plant growth has already been removed when passing through the leaves. This gives the light that magical ‘woodland’ quality, but it does make it harder for plants not adapted to woodlands to survive. Because of that, plants chosen for these areas need to be shade-loving, or enjoy dappled shade, and while many sun-loving plants will survive in building shade, they usually won’t in the shade beneath trees.
Shade from Evergreens
Evergreens, like Spruce, Fir, or large evergreen trees like southern magnolia, all present gardeners with more problems. Because they throw shade all year, that spring window of opportunity is gone, and the shade itself is often much denser, making the light-levels very low. Some evergreens, particularly most pine trees, do cast much lighter shade, and many plants that grow beneath deciduous trees will also grow beneath pines. They are much more ‘garden friendly’ than most other evergreens.
If the evergreens are some distance away, so that the garden area is open to the sky above, then it will be much the same as building shade, and allow a broad range of plants to grow. It is when the area is directly underneath the branches that problems arise. Some plants, like Japanese holly, Oregon grape, cherry laurel and sacred bamboo will grow in these locations, and are some of the best choices to go directly underneath those evergreen trees. Plants need to be described as grows in full shade to do well
The best approach is to keep evergreens with their branches right to the ground for as long as possible. Plant them where you won’t need to trim them up for access, and trim some of the upper branches so the lower ones stay alive. That way you won’t have the problem of planting beneath them to deal with at all.
Deep, Dry Shade
Here we are talking about those areas where thickly branched evergreens come down to within a few feet of the ground, yet the soil beneath is bare of anything green. Because of the overhead coverage, a lot of rain never even reaches the ground, so the area is both dry and dark. This is the hardest location to successfully plant, particularly if you cannot keep a steady supply of water coming. The best choices are periwinkle, big-root geranium and Japanese spurge, planted in big groups to fill the spaces, especially close around the tree trunks. Further out you will be more successful with a wider range of plants. Some gardeners just screen the area off with some taller shrubs planted further away, and hide the gap altogether.
You may think you have a shady garden, where not much will grow. Now you can go out and analyze that shade more carefully, taking note of what kinds you have. With that knowledge, you can make good choices of plants, and you will probably find you have a lot more options that you thought. A lot of very attractive plants grow best in certain kinds of shade, and without it our gardens would not be so varied and beautiful.