Archive for Sunday, March 9, 1997


March 9, 1997


A question-and-answer session offers some hints. But gardening will always require a bit of trial and error.

Gardeners are gearing up for spring. At the recent Garden Party sponsored by the Journal-World and Clinton Parkway Garden Store and Nursery, they asked question after question. Here is a sampling.

When is the best time to prune forsythia?

Pruning is a method of improving the appearance of a plant to remove dead or destroyed limbs or revitalize it. The timing of pruning is important for shrubs that produce flowers. Spring-blooming shrubs, such as forsythia, produce their flower buds on the wood that grew the previous year. Therefore, they should be pruned immediately after their flowering period.

Conversely, summer-flowering shrubs generally bear their flowers on wood that grew that season. These shrubs should be pruned in the fall when dormant or very early in the spring of the year before the growth starts

Avoid pruning any shrubs in the late summer. This will cause a second flush of new growth that will not have time to harden off before the first frost.

What can be done about clay soil?

This is a frequently asked question because much of the soil in this area contains a large proportion of clay. Working with and amending clay soil presents a challenge to area gardeners.

Soil is composed of water, air, organic and mineral matter. Each component exists in a different proportion. Ideally, the volume of soil should contain 25-35 percent water, 15-25 percent air and 5 percent organic matter. The remaining 45 percent is composed of mineral material. Pore spaces exist between solid particles and aggregates of particles. Water occupies the smaller spaces and air the larger voids.

The mineral portion of soil is a combination of sand, silt and clay. The proportion and the size of these particles greatly affect the properties of soil. The size of sand is large in comparison to the size of a particle of clay. As such, water easily passes through sand. Clay is just the opposite. Clay soil has poor aeration and poor drainage. It is slow to dry and becomes compacted if worked when wet. Yet, it crusts when it dries. Clay soil is also slow to warm in the spring.

The addition of organic material will greatly improve clay soil. Organic material improves the passage of water, is a source of nutrients for plants and serves as a food source for soil microorganisms. Because organic matter continues to break down in the soil over time, it should be added annually to clay soils. A good source of organic matter is compost.

How do you go about making a compost pile?

Compost is a mixture of soil and decayed organic material. It needs a combination of ``green'' matter, ``brown'' matter, oxygen and water. Sources of high nitrogen ``green'' organic matter are grass clippings, spent flowers and kitchen vegetable wastes. High-carbon ``brown'' matter includes leaves, straw and sawdust. The more shredded the material is prior to being tossed into the compost pile, the quicker the breakdown occurs.

The compost pile may be started in an out-of-the-way ``heap'' or bin that allows for moisture and air circulation. Chicken wire or wooden slats make suitable compost bins. Compost should be ``ready'' in four to six months after starting and will have an earthy smell to it. To quicken decomposition, the pile may be turned periodically. Commercial products also hasten the process.

Decomposition occurs when microorganisms such as fungi and bacteria secrete acids and enzymes that break down the cell wall of the organic matter placed in the compost pile. The fungi population rises rapidly. After four to five weeks, their activity causes the interior temperature to rise high enough to deactivate weed seeds. As the decay continues, the temperature diminishes, the fungi disappear and millions of bacteria continue the gradual breakdown of the organic material to a nutrient-rich humus.

Many gardeners keep two piles of compost going. One is being added to during the year while the other is ``finished'' and ready to use. If space is a problem and only one compost pile is possible, scoop out the matter at the bottom of the pile.

Can dog and cat manure be used in a compost pile?

No! The manure from these pets may harbor parasites and other pathogens that can be harmful to humans.

Can clematis be moved from one location to another?

Yes, clematis can be moved. Most plants prefer to be moved prior to their flush of growing activity. Clematis prefer a location where its roots can be shaded while the rest of the vine receives sun.

Can dogwood trees grow in this area?

Though Lawrence has a few brave gardeners who grow dogwood trees, they are generally not recommended for this area. The heat and dryness of Kansas summers put the tree to the test. Our cold winters often destroy the flower buds that had been set the previous summer.

Other trees, such as the redbud and flowering crabapple, are better suited to the area.

What about hydrangeas?

Depending on the microclimate, hydrangeas may also be considered marginal. Their hardiness is doubtful in hot, dry locations. They need protection from southwest winds.

Do any flowers grow under walnut trees?

The roots of walnut trees release a chemical called juglone that acts as a toxin to many plants. Some plants -- such as certain varieties of hostas, azaleas, tulips, daffodils, iris and ferns -- grow with indifference under the dappled shade walnut trees. Other plants or varieties are bothered by it.

Lists are available to help guide your selection. Like many things in the garden, growing plants under walnut trees sometimes requires a bit of trial and error.

What plant can be recommended to grow along a chain-link fence?

Depending on the amount of sun and shade along the fence and the effect the gardener is trying to achieve, a variety of planting material is available. If a camouflage of the fence is desired, vines, such as honeysuckle or morning glory, may be perfect. Tall flowers like coneflowers will also help to hide the fence, as will some of the tall ornamental grasses.

Use your imagination with plant combinations. The K-State Research and Extension-Douglas County has brochures with plant suggestions that may help you solve landscape problems such as this.

How can columbine be encouraged to spread in the garden?

Columbine will seed an area rapidly if the flower heads are left on after flowering and allowed to develop into seed. The seed is dispersed by the air. Success at moving new plants is best accomplished when seedlings are small. These delicate-looking perennials are not particularly long-lived and may need to be replanted every three years.

Take advantage of the horticultural expertise around town and in gardening books as your prepare your spring garden. Remember, the K-State Research and Extension-Douglas County will open its horticulture hotline April 1 to answer your gardening questions.

-- Carol Boncella is education coordinator at Lawrence Memorial Hospital and a Douglas County master gardener.

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