Those little sunshine icons on plant labels make light requirements seem so clear cut. But how much sun is partial sun? How deep is deep shade? And what about dappled shade — is that the same as partial sun?
Understanding the nuances of sun and shade can mean the difference between a plant that thrives or merely survives. Many plants will eke out an existence in the wrong light yet never reach their potential; a full-sun plant sited in shade may grow but it won't produce many flowers or fruit, while a shade plant in full sun may limp along exhibiting stunted growth or leaf damage.
Matching plants to the sun exposure they need prevents a lot of missteps — and getting a plant's location right the first time makes for a more sustainable and enjoyable garden. It all comes back to the much-repeated mantra of Master Gardeners: the right plant for the right place.
Often a plant's appearance offers clues about the particular type of light it requires. Shade-loving plants, such as hostas and ferns, often have large umbrella-like foliage, while sun-seekers may have smaller, even leathery or succulent leaves
A plant's origin also tells us what light it prefers. Prairie plants can withstand nonstop, unrelenting sun, while woodland plants do best in gentler, filtered light. Evergreen forests grow in dense shade, while savannas are open grasslands with scattered trees. Minnesota happens to have all of these biomes and, indeed, your own garden may contain each of these scenarios on a smaller scale.
In residential gardens, trees, structures and other features can affect the amount and quality of light that plants receive. Buildings and walls can block light in a solid, impenetrable manner but they can also reflect light. Water and pavement bounce light upward.
Trees and shrubs create shade that shifts and changes, depending upon the season and time of day. In spring, the area beneath deciduous trees resides temporarily in full sun, welcoming spring blooming bulbs and ephemerals until trees leaf out.
Roof overhangs and eaves may deter rain from reaching these shaded spots. A dense tree canopy also can limit the amount of moisture that falls within its shadow. Trees with roots close to the soil's surface compete with other plants for water and nutrients. In all cases, the resulting dry shade makes for one of the more challenging garden situations.
Get to know your garden
How do you determine what kind of sun and shade is in your own planting area? There is an app for that. Apps like Sun and Shade, Sun Seeker and FindMyShadow plot the path of the sun on your property. However, nothing beats your own observation in learning the subtler characteristics of your yard. "Get a chair and a cold beverage," as I heard Julie Weisenhorn, associate professor at the University of Minnesota, recommend on the radio the other day. "And spend some time getting to know your garden's sun and shade patterns."
Full sun is defined as at least six hours of direct sunlight a day. Many full-sun plants will be fine with 12 to 14 hours of sun, yet will appreciate a respite from the hottest afternoon sun. Plants with an additional drought-tolerance rating will do better in the hottest sun. Reflected light from a building or driveway, especially on the south side, can turn full sun into scorching. That kind of microclimate can be punishing for most plants.
Partial sun and partial shade sound like the same thing. Is this a trick question (or that glass half-full/half-empty thing)? Plants with these requirements need four to six hours of sun — however, that light is best when it's in the morning or evening. Harsh, overhead sun in the middle of the day is no friend to these plants. Plants designated for partial sun will do better with more sun, at least four hours, while those for partial shade will do better with no more than six hours of sun.
Dappled sun/shade falls into this same category. Tree leaves provide this type of filtered light as they sway with the breeze and as the sun moves through them during the day.
Full shade means less than three hours of direct sun per day. Ideally, those hours of sun are in the morning. Sometimes full shade is referred to as open shade or bright shade, such as the shade you find under high trees or in the shadow of buildings.
Deep shade doesn't mean darkness; all plants need some light to grow. Sometimes referred to as heavy or dense shade, this kind of shade is found under evergreen trees or on the north side of buildings with little direct light.
If your garden is shaded, don't despair. It's true you won't be growing tomatoes, but there's something to be said for gardening in a cool, serene setting while the summer sun blazes above.
Rhonda Fleming Hayes is a Minneapolis-based garden writer who blogs at thegardenbuzz.com. She is the author of "Pollinator-Friendly Gardening: Gardening for Bees, Butterflies and Other Pollinators," available at Amazon.com.
