Sun plants are those that are adapted to high levels of light. Their leaves can tolerate the high light and heat of the full sun, and they need those high light levels to grow their best. Without enough light, they stop producing flowers and fruit, growth slows, and they stretch toward the light. “Full sun” is usually defined as at least 6 hours a day of direct sunlight. Most sun plants produce adequately and look good with this much sun. However, they might do well with fewer hours of full sun if the shade that covers them the rest of the day is bright and open, with high levels of reflected light.
Sun plants that are being grown for their foliage will perform satisfactorily in less than full sun. A full-sun shrub might be very attractive, with an open, arching habit, in light shade. However, the fall color of their leaves may not be as vivid; high light levels produce more of the pigments that cause fall color.
Even full-sun plants can get too much sun. Locations that reflect light onto the plant from a white wall or cement driveway can be exceptionally hot. Look for plants adapted to deserts or extreme conditions for these spots, or moderate the heat somewhat by growing a vine on the wall or moving the plant a little farther back from the driveway.
You can use reflected light to get a little more light to plants that aren’t doing quite well enough, perhaps because a shadow passes over them in the afternoon. In the vegetable garden, place a white board or cardboard covered with aluminum foil on the south side of a tomato to boost its light levels. An aluminum foil mulch has much the same effect, and keeps down weeds, too.
Protection for Sun Plants
Most sun plants are more attractive if given some protection from the hottest afternoon sun. Nurseries often grow many of their sun plants under 30% shade cloth, which allows sufficient light but breaks the force of the full sun. The plants grow larger, greener leaves and look more lush in these conditions. However, plants that are grown for flowers or fruit might produce less with less light.