By Christina Perez

This article was adapted from a presentation entitled ‘Success in the Shade’.

Shade is an asset in the home garden. Just the image of dappled shade shifting softly over a wooden bench invites the mind to imagine and refresh. In the Piedmont region of North Carolina, our abundant deciduous trees and tall, stately evergreens make shade an inevitable part of the landscape. These shadowy areas have great potential, and with a little creativity and understanding of what shade plants need, the shade garden can become a focal point of the home garden.

Types of Shade

There are several distinct types of shade in the home garden. The first is filtered, or dappled, shade. This is characterized by the constant movement of light and shadow due to overhead tree branches. Filtered shade often gives the gardener the most options as many plants thrive in this light level^1,2. A second type is partial, or medium, shade. This type of shade changes as the day progresses; an area may be in shade for part of the day and full sun at other times. In general, partial shade zones receive four to six hours of shade per day^1,2. A third type of shade is open shade. Instead of being caused by tree branches, open shade occurs when a building or structure creates zones of shade. In general, open shade produces shade for three to four hours per day^1,2. The final type of shade is dense shade. Dense shade is found in heavily wooded areas as well as narrow side yards on the north facing side of homes and buildings. Dense shade is often the most challenging area to garden in successfully as relatively few plants prefer such reduced light levels^1,2

Shade Plant Adaptations

Apart from some parasitic plants, almost all plants capture sunlight in a process called photosynthesis. Many organisms, including humans, need to consume food to get energy. Plants, on the other hand, can make their own food. They have the wonderful capability of absorbing carbon dioxide from the air and water from the soil and converting it to sugar and an oxygen byproduct using the energy of the sun. Even plants that grow in shade need to be able to perform photosynthesis. These shade plants have several adaptations that allow them thrive in low light levels.

The first adaptation is leaf size. Because shade plants need to be able to perform photosynthesis to make their own food, they expend most of their energy absorbing enough light to make sugar. Large, wide leaves are an excellent way to capture the most light possible. This is often seen in shade plants such as Hosta ‘Amos’ and Colocasis ‘Thailand Giant’³. The second adaptation is leaf angle. Some plants are able to adjust the angle of their leaves to capture the maximum amount of light. Oxalis oregana is an understory herb in redwood forests in the western United States that is able to adjust the angle of its leaves to move with the progression of the sun through the forest⁴. Another important adaptation for shade plants is leaf surface. Some plants will alter aspects of their appearance depending on levels of light. For example, Cotyledon orbiculata will secrete a thick wax on its leaves and stem in high light environments to reflect light and prevent excessive water loss, but will not have a thick buildup of wax and will have flattened leaves to increased light absorption in low light levels⁵.

Site Preparation and Maintenance

Designing, preparing, and maintaining your shade garden is arguably the most important part of the process. The following are key steps in creating or redesigning your shady landscape:

Step 1: Test and Amend Your Soil: Learning about the components and nutrients in your garden soil is the foundation to success. This is the only way to know how you need to amend your soil to optimize it for your new shade plants. To obtain soil test kits and instructions, please visit the Master Gardener Volunteer office at 721 Foster Street Durham, NC 27701, or call 919-560-0536 Monday through Friday from 9:00am-4:00pm. Once you know the fertilizer and nutrient recommendations for your soil, make the required amendments before installing your shade plants.

Step 2: Make a Sun Plot: Often, we know that an area of the landscape is shady, but we rarely know exactly how much shade it has. This can be solved with a sun plot, a diagram that shows all of the areas of sun and shade in the garden throughout the day. To create a sun plot, draw out your property including all major structures, its orientation (does it face north, south, east, west, etc…), and the position of the sun. Now draw all of the shade on the property using a pencil. Try to capture the density of the shade by drawing it lightly and with gaps for dappled shade, or drawing it heavily to represent dense shade. Repeat this activity and create a sun plot for your property at 8:00am, 10:00am, 12:00pm, 2:00pm, 4:00pm, and 6:00pm. Once this is done, you will have the exact amount of sunlight each area of your property receives, and this will allow you to choose the correct plants for the various light levels. It is best to create a sun plot for your property for every season of the year as the position of the sun and leaf cover can change significantly throughout the year.

Step 3: Solve Your Problems: Before a new shade garden is installed, it is ideal to solve any problems that may exist in your garden site. For example, if the area drains poorly, install a drainage system; if the area is filled with weeds, weed the area properly; if your soil test recommends an amendment, make sure the recommendations are followed before any plants are installed. In the Piedmont, our most common requirement is to add organic matter to our dense clay soil to improve soil texture and drainage. Whatever your individual situation, be sure to assess your site and make any necessary improvements.

Step 4: Design Your Space: Shade gardens invite us to broaden our notions of what a garden should look like. Instead of bountiful blooms bouncing in the sun, think of spaces of calm and subdued hues where we can read, reflect, and get closer to nature. This is the time to think of incorporating elements in your space such as pathways, sitting areas, fences or gates, water features, a fire pit, and other focal points. Shade is the ideal place to relax and reflect, so consider creating an environment that invites these activities. Also think of installing a wild bird feeder to support our backyard birds and bring wonderful enjoyment to your shady retreat.

Step 5: Prepare and Maintain Your Space: Shady areas are often that way because of trees, so it is inevitable that we reflect on some important considerations in dealing with heavily rooted areas. Some trees, such as maples, have shallow root systems that make it almost impossible for plants to compete. If a landscape is filled with shallow roots, it may be best to accept this reality, put a fine wooden bench under your favorite tree, and place containers around it filled with shady loving plants. For wooded areas with deeper root systems, think small in your plant selection. Choose plants or shrubs with small root systems, and when planting, very carefully dig between tree roots to avoid damaging them. It is best to incorporate organic matter six inches into the soil between tree roots, but if this is not possible, try to incorporate it at least three to four inches². It may be tempting to build a raised bed around tree trunks and roots, but this is not an appropriate action. This can be potentially lethal for trees as raised soil around a tree trunk can cause the trunk to rot. Also, although it may seem like a great solution to raise the soil line to plant shade plants, tree roots will quickly invade that soil and out-compete the shade plants^1,2.

Once your new shade garden is installed, Water your shade plants deeply and less often to encourage deep root growth. Mulch your garden with two to three inches of mulch every year, and fertilize as necessary. Repeat your soil test every three years, and follow the recommendations specified by the reports.
References

1. Evans, E. Flowers and Woody Ornamentals. In: Evans, E., ed. The North Carolina Master Gardener Training Manual. 5th ed. Raleigh, NC: NC Cooperative Extension; 1998.

2. Miller, H. Gardening in the Shade. Horticulture Learn and Grow. University of Illinois Extension.

3. Givnish, T. J. 1988. Adaptation to Sun and Shade: A Whole-plant Perspective. Aust. J. Plant Physiol. 15, 63-92.

4. Hutchings, M.J., Harper John, E.A., Stewart, A.J.A. 2001. The Ecological Consequences of Environmental Heterogeneity: The 40th Symposium of the British Ecological Society. Held at the University of Sussex. Symposia of the British Ecological Society.
5. Robinson,, S.A., Lovelock, C.E., and Osmond, C.B. 1993. Wax as a Mechanism for Protection against Photoinhibition — A Study of Cotyledon orbiculata. Botanica Acta. 106(4): 307-312.
6. Martin, A. The Magical World of Moss Gardening. Portland, OR: Timber Press; 2015.