Hostas require deep to light shade to grow well. For best results, plant them in the spring in well-turned, moist soil and mulch to keep the roots at an even temperature. Water hostas generously, especially when they’re newly planted.
In general, the darker the hostas’ leaves, the more shade they need to be healthy. Planting under trees and shrubs is popular, but hostas can suffer when they have to compete with shallow roots. To have strong root systems, hostas must grow in well-turned earth and can become stunted if the ground packs too tightly around their roots. When caring for established hostas, it may be necessary to occasionally dig them up to turn and enrich the soil.
Native to areas of Japan, China and Korea that receive about 60 inches of rain a year, hostas require a generous amount of water, about an inch per week spring through fall, but none during the winter. Mulching with pine bark, pine straw or oak leaves enriches the soil and helps it retain moisture.
To reduce shock, pruning hostas, or dividing them during thinning, is best done in the spring before new growth is well underway. Once the eyes of the new leaves sprout, dig up the plant and divide it with a sharp knife. To prevent fungus growth, dip the knife in a 10 percent bleach solution before cutting, and wipe the cut plants with the solution as well.