When Should I Plant Hostas?

Hostas (Hosta spp. ) are popular perennials that typically are planted or transplanted in early spring and early fall. Gardeners have roughly 2,500 hosta varieties from which to choose, with the varieties offering a wide array of leaf sizes, shapes, colors and textures. Some hostas even produce fragrant blooms. Also known as plantain lilies, hostas are simple to care for and perfect for shade gardens. They are hardy in U.S. Department of Agriculture plant hardiness zones 3 through 8, depending on their variety.

One of the best times to plant or transplant hostas is in early spring after the last average annual frost date has passed. A late-spring frost can damage the plants' new leaves, however. So place plastic pots over emerging plants if freezing temperatures are predicted.

Hostas also can be planted or transplanted in early fall, or at least six weeks before the first average annual frost date. Six weeks is enough time for the plants to develop strong root systems before the ground freezes.

Although hostas do well in some shade, they do not tolerate deep shade. They thrive in locations with morning sunlight and afternoon shade. Hostas in full afternoon sunlight usually display leaf burn during summer. Hostas with blue leaves grow best in shade, and those with white, gold or yellow leaves do better with more sun exposure.

The ideal soil for hostas is loamy, slightly acidic and drains well. Add 6 inches of compost, manure, Canadian peat moss or other organic matter to the hosta bed, and mix it with the soil to a depth of 12 to 16 inches. The optimal pH level for hostas is 6.5 to 7.5.

Dig a 12-inch-deep planting hole for each hosta plant. Make the hole's width 1 1/2 times the anticipated size of the plant's root ball at maturity. The plant’s label should include the size of the hosta at maturity.

Tap around all sides of the container holding a hosta to loosen the soil and roots before removing the plant. Make vertical cuts in tangled root balls if necessary, using a tool that was sterilized with a household disinfectant, and shake loose soil from the roots. Do not add the loose soil to the planting hole. Plant your hosta in the hole at the same soil depth at which the plant grew in its container. Typically, the first set of leaves above the roots should be at ground level.

If your hosta came with bare roots, then soak the roots in lukewarm water for 30 minutes before planting. Build a small mound in the bottom of the planting hole, and spread the roots over the mound. Fill the hole with soil and water. Saturate the top 6 inches of soil around the plant with water.

Soak the soil around hostas with at least 1 inch of water each week. Early morning is the best time to water the plants. Signs that hostas are underwatered include drooping leaves and burned leaf tips.

Beginning in March in many U.S. locations, hostas alternate back and forth between producing leaves and roots. They have one or two cycles, or flushes, during which three or four oversized leaves emerge. These leaves take several weeks to open.

After the first flush's leaves open, the plants begin to harden off, or become accustomed to the conditions, and produce wax and purple pigments. At the completion of this leaf phase, the plants start producing white roots above roots they produced the previous year.

Soon the second flush begins with the emergence of three or four leaves. Keep the plants well-watered -- especially new plants and transplants -- because the leaves consist mostly of water.

Hostas bloom for about three or more weeks in summer. Each lilylike blossom opens at the top of a long, vertical shoot. Bees pollinate the flowers, which then create seedpods. The black seeds inside the seedpods ripen in six to eight weeks.

At the base of each blooming shoot, dormant buds emerge and become new shoots and leaves the next spring.

When hostas' yellow pigments become visible and their green leaves turn to gold in fall, it signals the plants are preparing for winter. At that time, it is too late to plant or transplant them.

Their ripe seedpods open, and the seeds take to the wind. The foliage remains through the first few freezes before shriveling. Flower stems persist until the first snowfall.

Before the first snow, remove all foliage and stems from the hostas. Apply a 2- to 3-inch-thick layer of mulch over the soil of hostas you planted or transplanted in spring or fall to protect the plants during winter.

During winter, hostas remain dormant, with no growth of any kind. Hostas require roughly 700 hours of temperatures below 40 degrees Fahrenheit. The longer the cold period lasts during their dormancy, the stronger the plants emerge in spring.