With more than 4,000 cultivars, hostas are emperors of the shade

A problem many gardeners face is what to plant in a shady area.

Perhaps no plant brightens a shade garden more than the hosta, said University of Missouri Extension horticulturist David Trinklein. The hardy perennial thrives in shade and is easy to grow.

“It is little wonder why hostas earned the title of ‘emperors of the shade,’” said Trinklein. “Their lush foliage brings attractive color to the shadiest of garden corners.”

Horticulturists estimate there are more than 4,000 cultivars of hostas. They range in size from several inches in diameter to giants with a height and spread of 48 inches when mature. Leaf color ranges from solid green, blue or yellow to variegated combinations of those colors. A few cultivars are viridescent, changing from lighter to darker shades during the growing season. Others are lutescent, changing from green to yellow. A very few change from yellow to white, a trait known as albescence.

Like day lilies, hostas bear a compound inflorescence known as a scape. Individual flowers on the spike are lavender or white, depending upon cultivar. Trinklein says some flowers are delightfully fragrant, adding further appeal to this attractive plant.

While hostas are considered shade plants, most will not thrive in deep, heavy shade. They prefer several hours of morning sun followed by afternoon shade, or broken patches of dappled sunlight. Hostas’ aggressive roots compete well with the roots of most tree species.

Generally, blue-leafed cultivars need shadier ground. Green- and yellow-leafed cultivars can tolerate more sun. Most sun-tolerant cultivars will exhibit some leaf-edge burn if exposed to afternoon sun and Midwestern summer heat.

Some hosta cultivars take years to develop into a mature clump. Good soil preparation is a sound investment, Trinklein said. Hostas prefer rich loam soil high in organic matter and slightly acidic. Good drainage also is important.

Mix about 4 inches of organic matter deeply into the soil to prepare average soil. Well-rotted manure, compost, leaf mold or peat are good sources of organic matter. Plant in a 12-inch-deep hole that is 1.5 times the cultivar’s mature diameter.

Divide dormant hostas for more plants or buy established plants in nursery containers. To plant, remove the hosta from its container and free any tangled roots. Put the plant in the hole so that soil covers the roots at the same level as in the nursery container. Remember that soil settles when watered. If planting dormant divisions, soak the roots in water for about 30 minutes before planting. Always water thoroughly after planting.

Experts disagree about the need to fertilize hostas. Some insist that most garden soil contains sufficient nutrients. Others say hostas need more fertilizer and suggest adding a granular, complete fertilizer such as 12-12-12 or 5-10-5 early in spring, followed by two more applications about six weeks apart. Apply according to label directions and consider the cultivar’s stature and vigor. Do not fertilize hostas after mid-July. This could stimulate late-season growth and prevent the plant from hardening for winter, Trinklein said.

Hostas need about 1 ½ inches of water per week during summer. Burned leaf tips and drooping leaves are a telltale sign of too little water. If hostas need extra irrigation, water early in the morning to allow leaves to dry quickly.

Control slugs and snails by using poison baits containing methiocarb, metaldehyde or iron phosphate. Place pans filled with beer in the garden. Pests will crawl into the pan and drown.

Other than foliar nematodes, hostas are relatively disease-free. Hosta virus X is a relatively new virus that has been getting a lot of publicity as of late, said Trinklein. Cultivars with light-colored leaves may show blue or green markings that usually follow the vein of the leaf into the surrounding tissue. This results in a mottled appearance. Leaves also may look lumpy or puckered.

Symptoms on cultivars with dark leaves are harder to detect and may appear as light-colored mottling instead of colored streaks. HVX spreads by mechanically transferring from an infected plant to a healthy one, especially during propagation. There is no cure and gardeners should rogue out infected plants, Trinklein said.

It is difficult to choose which of the 4,000 hosta cultivars to plant. Trinklein suggests looking for cultivars that have won awards from the American Hosta Society or the American Hosta Growers Association.

“Once considered a green filler for shady areas, hostas are now the stars of shady landscapes,” he said.

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