Monday, June 23, 2008

Marshall's Brief Guide to Hostas

Hostas are easy to grow, shade tolerant, herbaceous perennials. Grown mainly for their beautiful foliage, hostas exist in a wide range of shapes, colors, sizes, and textures. They were once classified in the family Liliaceae but are now included in the family Agavaceae. Hostas are also called plantain lilies or Funkia, but these names are outdated. The scientific name for hosta is also its common name.

Hostas, native to Japan, Korea, and China, were imported to North America in the mid-1800s. From the handful of species that were imported, hybridizing and tissue culture propagation have increased options for today's gardeners as there are many species and thousands of cultivars available.

If we're at all familiar with gardens, the name hosta evokes an image of a low-growing green plant with large broad leaves. To be more specific, a hosta is a non-bulbous lily that is a shade tolerant, hardy perennial plant grown principally for its foliage. But hostas produce pendulous 1" to 2" long white or violet flowers on an erect panicle up to 31" tall.

Hostas are hardy in USDA zones 3 through 8, meaning they grow in most areas except deserts and the tropics or subtropics. They need about 700 hours below 40 degrees F to meet their dormancy requirements.

Hostas prefer moist, light, humus-based acid soil. The soil should be rich in organic matter and it can be any form: peat moss, rotted or composted manure, rotted sawdust, or composted leaves. By adding large quantities of organic matter, moisture retention and aeration of the soil is improved. Due in part to their leaf size, hostas have a very high transpiration rate, and so soil conditions should allow for optimum water retention.

Keep in mind that with hostas, whichever you choose, you really can not go wrong. However, there are two keys to growing hostas successfully: light and water. Most newcomers think all hostas do best in full shade, but this isn't true. Hostas tolerate varying degrees of shade, yet some like the sun. Each variety of hosta has a different light requirement, so you can plant hostas in almost any light situation. Generally, blue hostas prefer more shade and the gold and yellow-colored varieties tolerate and receive their best coloring from more sun. If you have dense shade, you might want more variegated ones to help brighten the areas.

Preferring a well-drained location, hostas generally need more water than the rain provides in an average year. This is true especially if growing under trees which take up much soil moisture. Plants in ideal growth conditions receive 1 1/2" per week. Over the course of a season that is 3/4" every 3 to 4 days. Hostas need this extra water during the growing season, but not in winter when they are dormant. Too much water in winter can contribute to crown or root rot.

Hostas need room and about two seasons to grow and achieve their full potential. When planting, space the small-leaved hostas between 18" and 24" apart and the large-leaved ones 24" to 30" apart. Space them appropriately to allow room for growth since hostas do best when left undisturbed for several years.
After they are planted, your hostas will require little care. Attentive watering and well-drained soil are musts, and a layer of mulch (no more than 2-3") will prevent competition from weeds. Annual feeding with slow-release fertilizer will keep your hostas happy. With so many different options in fertilizer, the thing to do is to take a soil sample to your local Cooperative Extension Office for testing and fertilize according to recommendations.

Place your hostas in soil that is loose and well-drained in a shady spot that is protected from hot afternoon sun. Amend the soil with organic matter or compost. Add a slow-release fertilizer to the soil. Place the hosta in the hole so that the clump is level with the soil surface, and water thoroughly. You can plant them any time during the growing season, but the later in the season you plant, the more important it is to keep them adequately watered. Cutting off the flower scape as soon as possible after blooming tends to increase the probability of re-bloom.

Hostas do not need regular dividing to keep them vigorous. They can be left undisturbed indefinitely, but when dividing is necessary, do so in the spring just after the plant pips are emerging from the ground so the new foliage is not damaged. If the plants are left undivided, you can enjoy their mature beauty sooner.

Hostas are virtually disease-free. Major pests include slugs and snails, deer, cut-worms and leaf beetles. Slugs chew holes in the hosta leaves and make them unsightly. There are books about slug control methods including: picking them off one by one, leaving out beer-filled trays in the hopes the slugs drown, copper rings, squashing them between bricks, pesticides, and my favorite, diatomaceous earth. It is a powder of the finely ground shells of diatoms. Diatoms are microscopic sea creatures. When sprinkled on the ground, the slugs crawl over the powder, cutting themselves all to pieces, then they die of dehydration.

Deer love hostas. Apart from keeping a dog present in the affected area, there is no single cure for deer. Previously successful methods of repellent, such as leaving bags of human hair around, are no longer effective because urban deer have become comfortable co-existing with humans. A varied program with several components will be more effective than a single preventive method. Contact local nurseries for information on deer repellent products currently on the market. Rabbits and squirrels may chew an occasional leaf, but are not generally known to be problems for hostas.

Cut-worms and leaf beetles can cause more damage than slugs. Cut-worms live in the ground and feed at night by crawling up the plant and eating holes through the unopened leaves. Leaf beetles will eat holes in the center of the leaves between the veins. Sometimes this can be confused with slug damage. A natural control is the house wren. They have a tremendous appetite for those pests and for slugs. If you're not keen on birdhouses, you can fall back on commercially available pesticides. Always carefully follow label instructions and heed warnings.

Now that you're an expert on hostas, how do you pick the right ones? Think about the space you have available and the amount of the sunlight the plant will receive in your garden. Those are determining factors.

Here are a few varieties to consider:

x'Sum and Substance' - A striking hosta with large, leathery, neutral-green leaves. It has been called "the biggest and most popular hosta in the world." It grows to 3' tall and 5-6' across.

x'Blue Angel' - The largest and most dramatic-looking of all hostas, 'Blue Angel' has deep blue-green leaves and can grow into a mount 30" tall and 6' wide.

x'Emily Dickenson' - Deep green glossy leaves with creamy white margins, a neat, compact, mounded habit, and deep lavender flowers make this a welcome plant in any garden. It grows to 20" tall and 26" wide.

x'Praying Hands' - The most unusual hosta to appear. The plant has extremely narrow, curled, crinkled and furrowed green-and-white leaves that some believe resemble hands folded in prayer. It forms clumps about 18" wide and in late summer bears 18" tall spikes of light-lavender flowers.

x'June' - Heavy leaves with blue-green margins, gold centers with green striations within the gold, and bright color in the shade. It grows to 15" tall and 15" wide. Bears very fragrant violet flowers from July to August.

Ready for a carefree, lush plant to cover your problem shade areas or to provide a sense of calm to your garden? You're ready for a hosta.

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