Extension News

Horticultural Thoughts with Dr. Grow-It-All

Note to media editors:

Garden column for the week of Jan. 28

There is no photo for this week's column.


By James Romer
Extension Horticulturist
Iowa State University

Dear Dr. Grow-It-All,

Every year my Mom takes it upon herself to absolutely hack the trees in our backyard. She calls it pruning. I call it butchering. If this was a football game, there would most certainly be a foul for illegal use of the pruning saw or false start of the chainsaw. It's so bad that we fear for our lives. I love my Mom and I love the trees, but I can't figure out a way in which to tell her to put the chainsaw down and let the trees be. Help me please!!

Out on a Limb in Forest Home

Dear Out on a Limb;

The late dormant period (February to early April) is an excellent time to prune deciduous trees. The absence of foliage at this time of year gives the home gardener a clear view of the tree and allows him/her to select and remove appropriate branches. Also, the "healing" processes (wound compartmentalization and callus formation) occur most rapidly just prior to the onset of growth in spring. Proper pruning improves the appearance, maintains the health and prolongs the life of trees. Improper pruning destroys their natural beauty, weakens them and may lead to their premature death.

It is essential to make proper cuts when pruning trees. Do not make flush cuts. These are types of cuts made as close as possible to the trunk or main branch. Flush cuts produce large wounds, destroy the tree's natural mechanisms that promote healing, and slow the healing process. When pruning trees, make the final cut just beyond the branch collar and branch bark ridge. The branch collar is the swollen area at the base of the branch. The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk. When a branch is pruned properly, a slightly raised area remains on the trunk or main branch. However, do not leave stubs.

Use the three-cut procedure when cutting branches greater than one-inch in diameter. This technique prevents the branch from breaking off and stripping bark from the trunk or main branch. Make the first cut about one to two feet from the main branch or trunk. Cut upward and go about halfway through the branch. Make the second cut a few inches beyond the first. Cut downward completely through the branch. Remove the remaining portion of the branch by making the third and final cut just beyond the branch collar.

Do not apply wound dressings or pruning paints to the cut surface. The application of wound dressings or paints doesn't stop decay and may actually inhibit or delay the healing of wounds. There is one exception to the no paint recommendation. That exception involves oak trees. Oak trees should not be pruned from April 1 to July 1 to reduce the risk of the spread of oak wilt. If you must prune oaks between April 1 and July 1, for example to correct storm damage, apply a dilute latex paint solution to all cut surfaces.

Some trees, such as maple, birch and elm, bleed heavily when pruned in late winter or early spring. However, the heavy bleeding causes little damage to trees. (The trees won't bleed to death.) Eventually the flow of sap will slow and stop. Heavy bleeding of susceptible trees can be avoided by pruning in late June or early July.

The pruning of deciduous trees by the home gardener should be limited to small trees and the removal of smaller branches that can be reached from the ground in medium to large trees. Branches high up in large trees and those near utility lines should be left to professional arborists. Professional arborists should have the proper training and equipment to safely perform the job. Hopefully, this will help your Mom to avoid any calls of roughing the red oak.

Dear Dr. Grow-It-All,

My boss has these spindly weak-looking plants in his office. They look terrible! However, he takes great pride in them. I guess beauty is in the eye of the beholder, but it's enough to make one wonder about his eyesight. I'm looking for something to slip under his door so that those plants can get the attention they need to look better. Is there anything you can give me to turn those struggling plants around?

Barley Lit in Britt

Dear Barely Lit;

Many plants don't receive sufficient light in the winter because of the short days, low angle of the sun, and often overcast weather. While houseplants differ in their lighting requirements, all would benefit from supplemental lighting during the winter months.

The key to growing healthy houseplants is the light source. Most homes are lit with incandescent bulbs. Unfortunately, they are not a good light source for houseplants. Incandescent bulbs emit light primarily in the red portion of the visible light spectrum. They also are inefficient, 75 to 85 percent of the energy is lost as heat. Foliage that comes into contact with a hot incandescent bulb will be burned.

Fluorescent bulbs are a better source of light for houseplants. Fluorescent tubes give off little heat and produce two and a half to three times more light than incandescent bulbs of the same wattage. They also produce light over a broader range of the visible spectrum, however, blue is predominant. In addition, they are available in square, tubular and round shapes. Fluorescent lamps are also available in various colors, such as cool and warm whites, daylight and natural. Warm white fluorescent tubes emit a higher percentage of red light.

Fluorescent plant lights (commonly referred to as "grow lights") are also available to indoor gardeners. They emit light primarily in the red and blue regions of the light spectrum. However, "grow lights" give off less light than standard fluorescent lights and are quite expensive. A fluorescent unit containing two standard 40 watt fluorescent tubes or one cool white and one warm white tube provides adequate light for house plants and is much more economical.

In well-lit locations, artificial light may be needed only for a few hours in the evening during the fall and winter months. In darker areas, operate the lights for 12 to 16 hours per day. Since light intensity drops rapidly as the distance from the light source increases, houseplants should be placed within a few inches of the lights. Place plants that require lots of light directly under the lights, and those that can tolerate lower light levels to the side.

Contacts :

James Romer, Horticulture, (515) 294-2336, jromer@iastate.edu

Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu