Metro-East Living

Trees and need nitrogen every year but don’t add trace elements

By Charles Giedeman

Pruning back clematis can rejuvenate it.
Pruning back clematis can rejuvenate it. Newport News Daily Press

Q: Is this the time of the year to fertilize trees and shrubs? We have several young trees and shrubs, which may need it if this the right time. What fertilizer should we use?

F.L. of Millstadt

A: Most of the nutrients trees and shrubs need will be provided by the soil itself. These are termed micronutrients. They are needed in such small amounts that if you apply them, you could be giving these plants too much of these trace elements, setting back the plant.

Your fertilizer application can still be made this spring before the leaves begin to bud out.

You mainly need to be concerned with applying nitrogen, phosphorous and potassium (potash). Nitrogen is can dissolve in water and may be moved out of the root zone to other locations where the tree may not be able to obtain it. Nitrogen needs to be applied almost every year and should be applied in two smaller applications, in spring and in fall as the leaves are dropping. Phosphorous and potassium stay in the soil longer, which means you need to apply them only about once every three years.

The best area to apply the fertilizer is just outside the drip line (which is an imaginary line just outside the tip of the branches as you look up to the outside of the tree. Just think of an umbrella shedding water; the tree reacts the same way. You can apply the fertilizer by a spreader in this area or digging 2-inch-diameter holes about 1 foot deep spaced at regular intervals in the drip area. The latter application will encourage the roots of the tree to grow deeper. Two to four pounds of actual nitrogen are needed to fertilize the whole tree for a year (The first fertilize number is for percent of nitrogen. Divide this into 100 to find the actual pounds of fertilizer for 1 pound of actual nitrogen.)

Q: I have an old clematis plant that has bloomed very well with no special attention. But for the past three years, the plant grows well but produces no new floral displays. The leaves produced usually turn yellow right after they appear. The plant usually doesn’t grow as well either. What could be the problem?

M. R. of Belleville

A: Age is the problem. You will have prune to rejuvenate the plant. Before it begins to grow this spring, prune off any old discolored branches. This process will stimulate the plant to form new shoots, which will produce the flowers. Every year after this year, prune off 1/3 of the older branches closer to the base of the plant to keep stimulating the plant to produce younger tissues. This is called rejuvenating pruning, which works for other older shrubs that do not bloom as well as they used to.

Charles Giedeman is a local contributing writer. Send your gardening questions to Lifestyle Editor Patrick Kuhl, Belleville News-Democrat, P.O. Box 427, 120 S. Illinois St., Belleville, IL 62222-0427, or email them to pkuhl@bnd.com.

Use a shovel or check out a soil probe to collect samples that will help tell you what your garden needs.

Do it now

  • Gradually take your vegetable plants outside to begin hardening them off with the variations of temperatures.
  • Apply dormant oil to landscape plants and fruit trees to kill scale insects and mites before they hatch.
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