A garden shaded by large trees can be a challenge, but the cool light offers a respite for many perennials. There are many plants that do not require full sun to thrive. Partial shade generally is defined as three to four hours of sun. It may mean dappled sunlight or be more evenly divided between light and shade.
Astilbe (Astilbe x arendsii), also called False Spirea, loves to grow in moist, partially shady sites. There are many varieties, with foliage varying from dark green to reddish green, and the feathery flowery spikes in red, pink, white, peach and purple. Astilbe blooms in June and July, and it thrives in USDA Hardiness Zones 4 to 9. Astilbe grows in neat mounds, making it an excellent border plant.
Hostas (Hosta spp.) are the workhorse of the shade garden. They are easy to grow and require little maintenance once established. There are many varieties available of this hardy herbaceous perennial. Hostas are grown for their foliage, which comes in combinations of green, gold, white and blue, variegated and solid, leathery or smooth. Blue-tinged hostas do not grow as well in partial shade; they need deep shade for best color. Hostas do produce flower spikes, with white, purple or blue blooms. Hostas make excellent ground covers and specimen plants. They need rich organic soil and thrive in USDA zones 3 to 9.
Siberian bugloss (Brunnera macrophylla) has blue, forget-me-not-like flowers that brighten the garden in April and May. This plant, which has heart-shaped blackish-green leaves, grows to 18 inches tall and prefers partial to full shade. Siberian bugloss, a clump-forming perennial, is somewhat drought tolerant but needs well-drained organic soil. Siberian bugloss thrives in USDA zones 3 to 8.
Columbine (Aquilegia spp.) is a bushy perennial that grows to 2 feet tall and wide. It has low-growing leaves and long flower spikes. The blooms' five petals and five sepals come in a variety of colors, including white, pink, blue, indigo, red and yellow. Columbine is native to the Rocky Mountains, and it does not like full sun. It prefers partial shade, rich moist soil and good drainage. Columbine grows in USDA zones 3 to 8. The plant lives only two to three years, but it reseeds very easily.