The Effects of Light

Light brings warmth with it. A building basking in summer sunlight often retains much of the sun's heat, and sometimes a corner will act as a heat trap. Temperatures can rise quite high in the afternoon, then decline by 10 degrees F or more within an hour after sunlight ceases to shine on the area. Take care when planting perennials in these situations because they must cope not only with light, but also with intense heat in summer.

Dappled light, the kind that filters through trees, is an even more complex factor. Dappled or filtered light not only changes with the season and time of day, but also with changes in leaf growth of the trees overhead.

Since shade is so variable, then, experiment with your own light conditions. Although you might read that a plant is suitable for shade, you may discover that in your particular shaded spot it needs just a bit more light in order to thrive.

You can always help a plant adapt better to your garden by altering the light. In wooded areas, you can increase light by lopping off the lower limbs of trees or by thinning out shrubs. You can lighten the dark corners of a building by painting the building white or by adding reflectors in the form of brilliant white pebbles in an adjacent terrace or path.

In sunny areas, you can reduce the amount of light your plants receive. Trellises, arbors, and lath houses are ideal for shading plants and thus reducing the heat. These structures are often used in southern gardens to prevent heat-induced dormancy. Nature can also be used to reduce the amount of sunlight reaching your perennials, although this takes a little longer. Just plant a hedge or border of tall shrubs or small trees along the south side of the garden.