Growing Lawns Under Shaded Conditions
The establishment and maintenance of good quality lawns under shaded conditions may be possible if the basic requirements are known and understood. Trees have extensive root systems which enable them to take up huge amounts of water and nutrients from the soil. Dense leaf canopies decrease the light intensity reaching grass which grows underneath the trees. These factors -- competition for water, nutrients and light, as well as improper lawn care practices (i.e. too frequent irrigation) are some of the basic causes of turf failure under shaded conditions.
The following suggestions should help you establish a reasonably good lawn in shady sites:
Even under the best conditions, you should realize that you may still have a thin lawn in moderate shade. In many cases it is unrealistic to expect more.
- Use grasses which are somewhat shade tolerant. Fine leaf fescues have been found to be the best grass type to use in shade if the soil conditions are dry. There are several fine leaf fescue cultivars which have good to excellent shade tolerance. These should comprise the larger percentage of your grass mix, 60-80%. In addition, the mix could contain 10% perennial ryegrass and the remainder a blend of shade-tolerant Kentucky bluegrass. Use this mixture at the rate of 4-5 lbs. per 1,000 sq.ft.
Another possibility in this situation are those tall fescue varieties which show good tolerance to shade. Tall fescues are grown as a monoculture (not mixed with other grass types).
There are several varieties of Kentucky bluegrass which will tolerate moderate amounts of shade. If the site is moderately shady, consider using an 80% shade-tolerant Kentucky bluegrass blend with the remaining 20% perennial ryegrass. Use the mixture at the rate of 3-4 lbs. per 1,000 sq.ft. These shade-tolerant Kentucky bluegrass varieties are sometimes included in those mixtures dominated by fine leaf fescues.
If shade and wet soil conditions exist then consider using a mixture containing 70% Poa trivialis, commonly referred to as rough bluegrass. The remainder of the mixture can be 30% shade- tolerant Kentucky bluegrass blend. Use the mixture at 2-3 lbs. per 1,000 sq.ft.
- Fertilize a lawn in the shade lightly in the spring (Memorial Day) and again in late summer (Labor Day). If trees need to be fertilized use sub-surface application methods (i.e. liquid root fertilizing). In both cases use slow-release fertilizers.
- Irrigation in shady sites will not be needed as often as those lawns growing in full sun. Fine leaf fescues in most summers may not require any supplemental irrigation. Frequent irrigation of fine leaf fescues in shade will result in them growing poorly. If needed, provide deep (long duration) and infrequent (no more than once every few weeks) supplemental irrigation.
- Maintain soil pH to encourage good overall turfgrass growth. Have your soil tested and apply recommended amounts of limestone to maintain the pH between 6.0 and 7.0.
- Remove those trees which do not contribute significantly to the overall landscape plan. Often you must decide whether you want trees or grass.
- Trees which are properly pruned by a qualified arborist will allow more sunlight to reach the grass growing beneath them. Usually this involves removal of certain lower branches as well as the selective removal of interior branches in the crown area of the tree. Avoid extensive or drastic pruning.
- Plant new trees wisely taking into consideration the number and density of the trees.
- Plant tree species which provide open shade rather than dense shade. Also avoid those species known for their habit of producing large amounts of surface roots (i.e., Norway maple).
- Be sure soils have proper drainage and aeration to allow penetration of nutrients, water and air. This allows grass to grow better and discourages trees from establishing roots near the surface.
- Start lawns (in the shade and sun) during the late summer rather than spring. It is a much better time of the year for a new lawn to establish.
- Lawns in shade should be mowed at heights of two to three inches. Mow the lawn frequently so you never remove more than 1/3 of the leaf blade at any one time.
- Grasses in shade may be more tender. Reduce to a minimum the amount of traffic over a lawn in the shade for best results.
- Do not allow leaves (and other debris) to accumulate on the lawn which could potentially smother the grass.
- Where shade and competition from tree roots are too limiting consider alternatives to grass.
- Certain ground cover plants will tolerate shade, but not necessarily the competition associated with tree roots.
- A few inch layer of an organic bark mulch (large particle size) is often the best solution when all else fails. Avoid having mulches come into contact with the bark at the base of the tree.
Resource: Home Lawns, by Mary C. Thurn, Norman W. Hummel and A. M. Petrovic, Information Bulletin 185 (revised edition), A Cornell Cooperative Extension Publication, 11/94.
11/94 Prepared by: Thomas Kowalsick, Cornell Cooperative Extension, Suffolk County