Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

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How do I grow clematis?

Fast-growing perennial clematis vines are well known for their beautiful flowers. Clematis vines will bloom in spring, summer or fall, depending upon the specific varieties. Clematis vines require sun to partial shade and need trellises or some other kind of support.

The key to growing healthy clematis is to see that they have hot heads and cool feet. That is, the vines and foliage should be in the sun and the root areas should be shaded so that they are cooler. Provide shade for the roots by planting clematis on the shady side of a boulder, wall or other object. Annuals, perennials or shrubs also can provide shade for the clematis roots. The soil around clematis roots should be rich, cool and moist.

Grow the large-flowered clematis on fences, trellises, lamp posts, arbors or other structures. Or emulate English gardeners by growing clematis vines over yews and other shrubs or small trees. The vines will scramble over the foliage, reaching up toward sunlight. The vertical growth of vines is valuable in small garden spaces. Vines also will soften the lines of building walls and other hard constructions.

Spring and fall are the best times to plant clematis although container-grown plants can be planted throughout the growing season. Look for vigorous plants that are about two years old. They will have well-developed roots.

Clematis plants will thrive when grown in a well-draining organic soil that has loose, friable structure. Dig a planting hole that is ample, two feet deep and two feet in diameter. Fill the hole with a rich well-draining mixture of loam, peat moss, dried cow manure and super phosphate. Since clematis grows very well in basic soils, check the pH of your soil. If it is at neutral (7.0) or on the acid side (less than 7.0), add lime to the soil at recommended rates. Every couple of years, retest the soil pH, especially if the clematis is not performing as well as you would like.

Scratch well-rotted manure into the soil a couple of times a year--as with any ornamentals, be careful not to injure to roots. Clematis are heavy feeder so you may want to give them periodic feedings of liquid fertilizer that is formulated for flowering plants, during spring and early summer.

At first, you may have to help clematis grow on a fence or trellis. Support the stems on the trellis with loose ties.

Plan to encourage the development of six to eight stems during the first year. During the first spring, cut the vine back to about one foot after planting to force branching near the base. Then through spring and early summer, pinch the growing ends back higher and higher to force more branching. It is far better to have more branching and less flowers during the first year in your garden. The more you prune to encourage branching during the first year, the better will be the appearance of your clematis.

Gardeners will be happy to hear that clematis are not likely to be bothered by pests and diseases. The worst problem is likely to be clematis wilt, a fungal disease that rarely proves fatal. If a plant is infected, cut it back to the ground and remove the foliage and vines from the garden. The plant clematis probably will come back again from the roots. Mildew can be a problem if left unchecked during a year of heavy infestation--spray at the first signs with a fungicide such as funginex. As an alternative, try a home remedy consisting of one tablespoon of baking soda, one tablespoon of horticultural oil and one tablespoon of liquid detergent in a gallon of water.