Although summer this year has been slow to produce any real heat, I am relatively sure it will come. In the meantime our cool crops are loving the very extended spring!
The lawn is a big fixture in the landscape but it is largely not understood. What happens often in the landscape is the competition that happens between the trees we adore and the lawn surrounding them as they are competing for the same light and moisture. What began as a lush lawn with small, immature trees has over the years become a thin, weedy lawn shaded by large, mature trees.
It is nice to have harmony between your trees and turf areas, however it is important to realize a landscape is a living entity, growing over time and causing an evolution of sorts to occur. The trees are necessary for shade, windbreak and beauty and have the double duty of cleaning our air of pollutants, producing oxygen and providing habitat and food for a host of insects, birds and other critters. The lawns also help to clean our air (on a lesser scale), control erosion, produce oxygen and provide a decadent surface for us humanoids to lie on, walk on and endlessly care for.
Both trees and turf compete for water, nutrients and light. By reducing the amount of competition it is possible to live in harmony and in fact have the best of both. Most of the type of turf grasses will not grow well if they get less than six hours of direct sun daily. If your turf is thin and weedy underneath your trees, you may want to either prune up the tree to allow more light and water a bit more. If that is not a suitable conflict resolution, then perhaps it is best to have something else where that turf is currently growing. An option may be a type of grass that is more tolerant of shade like some of the fine fescues or rough bluegrass. Alternatively, making that area into a perennial shade garden or if the competition is severe to simply mulch under the trees with an organic surface mulch.
Another consideration is to think about the competition that is below ground. Trees with spreading root systems are heavy competitors for moisture and many of the roots are in the top couple feet of soil. If turf under trees is sickly it is a good idea to fertilize but at half strength as there is less turf to fertilize. Using a fertilizer that is not high in nitrogen is also recommended as you want to nurture the underground parts of the grass and high nitrogen promotes succulent top growth. Fertilizer formulations with a higher amount of potassium will help promote stronger leaf blades and make the turf a bit more tolerant to wear. It is also recommended to use a slow release formulation as well.
Turf needs about an inch of water a week for the best growth. Under trees there is much less available moisture - it can be 30 or 40 per cent lower - so ensure you take the time to water these areas deeply and thoroughly. Frequent shallow watering will form shallow roots on the turf that will dry out even more quickly.
Try to limit the traffic on the lawn in these shady areas as they will not recover as quickly as turf growing in full sun. Remove any leaves and branches that fall promptly as the grass in the shade needs all the light it can get. Overseed in spring to help fill in thin and bare patches.
Last but not least, mow the turf under trees a bit higher than the turf in full sun. It is important to remove about a third of the blades at each mowing and leave the clippings to replenish nutrients and organic matter back into the soil.
- Hanbidge is a horticulturist with the Saskatoon School of Horticulture and can be reached at 306-931-GROW(4769); by email [email protected] check out our website atsaskhort.com
