False spirea (Sorbaria sorbifolia) Zones: 2-9 Size: 6 feet tall 10 feet wide Conditions: Full sun to partial shade; moist, well-drained soil Forms large masses of arching branches covered with green pinnate leaves. Billowy white sprays of flowers in mid- to late summer. Mature plants spread where you let them. Unbelievably durable and will take any soil. Annual or occasional decapitation to the ground is a good idea because it helps keep the plant under control.