Regional Gardening Reports :: National Gardening Association

In the Garden:
Lower South
July, 2010
Regional Report

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This bright dappled shade provides the turf beneath its canopy enough light to stay dense and healthy.

Of Turf and Trees

Gardeners across the country love trees. Yet in a lower south summer trees are appreciated for more than their majesty and beauty. Trees make summer bearable...perhaps I should say, survivable!

A great shade tree stands as a shield against the brutal rays of the summer sun, creating a habitable zone beneath its boughs for us to relax or play.

We also love turf. It is a green outdoor carpet on which we run and play. It also provides a key foundational element of traditional landscape design and moderates the summer temperatures by absorbing rather than reflecting the solar rays.

So we love our trees and turf, but alas they are not so fond of each other! They compete with each other for water and nutrients. Additionally, from the grass's perspective, trees rob sunlight required for their leaf blades to make carbohydrates, the fuel for growth and good health.

Most of our southern turf species can tolerate some shade. St. Augustine is fairly shade tolerant if the shade is very bright or with some part day sun. Zoysia and Centipede are less shade adaptable and Bermudagrass just can't do without more direct sunlight.

So what are we to do? The solution is to create an environment where both turf and trees can thrive. Trees need a mulched area around them when they are young. This keeps the grass away from the tree avoiding the inevitable damage to the trunk from mowers and string trimmers.

For the first five years or more maintain a wide mulched area, preferably out to the edge of the tree's canopy. This reduces competition from the turf grass for water and nutrients. The result is more growth for the tree during these early years. Supplemental water and fertilizer for the tree is also helpful during these early years. The goal is to get them to "shade sized" as soon as possible.

Once a tree reaches a large size and starts to cast a wide shade area the goal is to maintain good health rather than promote growth. This won't require extra fertilizer, but during an extended drought some infrequent deep soakings will be helpful.

Turf on the other hand will start to suffer as the tree canopy above it creates an increasingly dense shade. There are several things we can do to help the turf to remain healthy and to promote a denser lawn.

Some judicious pruning can be done to increase the light intensity. This may include some thinning of the canopy, which means a very light removal of selected branches where they join another branch. This can easily be overdone to the detriment of the tree, so involve a professional arborist in this process.

Removal of low hanging branches can also be helpful in allowing some incidental light in from around the canopy. When pruning a tree to benefit the turf beneath it remember that a tree will respond to excessive pruning with a lot of regrowth in the area of the pruning cuts, often ending up in more dense shade than before.

The leaf blades of the grass plant are its solar panels. They collect the sun in the plant's food factories to support growth and thus promote a healthy dense lawn. If you mow grass short in the shade you will essentially be limiting its ability to capture what little sunlight is reaching the ground.

Set your mower a little higher to leave a little more leaf blade to capture the limited light and not only will your turf maintain its density better but it will look thicker too. This doesn't mean to mow less often; just mow at a higher setting.

Finally, don't try to replace sunlight with fertilizer. It won't work and the excessive nutrition may actually work to create a less resilient grass plant.

So here's to a beautiful lawn AND some nice shade trees to make our southern summers a little more habitable outdoors.

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