Turf is a balanced system. This is why sunny areas of your lawn may respond differently to maintenance techniques than shady areas of your lawn. In other words, the turfgrass plant receiving less light will require less moisture and less fertilizer, but will need more attention in other respects. This article explains many of the steps necessary to establish and maintain nice grass in the shade.
Like all plants, turfgrasses need light to grow. Even the most shade-tolerant varieties of turf need a minimum of 2-3 hours of sunlight per day. The best results for establishing turf are by seeding. Do not try to sod heavy shade. The cost will be higher and the results will be temporary (at best). Early fall is the best time to seed, but for lawns with severe shade problems, early spring seeding may be preferable. Be sure that when aerating you are not doing more harm than good to established turf. Bio Green’s shady blend, recommended for the Northern Virginia area, is a mixture of fine fescue, Kentucky bluegrass and tall fescue.
Properly pruning and thinning trees can help with shady turf. In most cases, proper pruning will help (not hurt) the overall health of the trees. Pruning not only lets more light reach the grass below, but it also increases airflow. Increased airflow helps to eliminate conditions that favor the spread of disease. Dead, diseased, crossed, and lower limbs are good candidates for removal. Bear in mind that surface roots can be pruned as well as branches. In many cases, it is a healthier alternative to the “skinning” surface roots receive from mowers/string trimmers.
Besides a lack of sunlight, the biggest factor limiting grass growth is the competition from tree roots. Fighting for space, water and nutrients between the root system of your lawn and a mature tree is a losing battle for the grass. To help the grass roots better compete, remember that watering grass beneath the drip line of mature trees will have its own specific schedule. While turf needs little supplemental irrigation in the Spring and Fall, when the water table drops during the heat of summer, these areas will get stressed. Deep, infrequent watering is best. In addition, the soil tends to be much more acidic under trees (which will limit root growth due to aluminum toxicity) so these areas will need more frequent, heavier lime treatment.
Diseases like powdery mildew, brown patch, and leaf spot are sometimes a dominant factor that limits turf survival in the shade. Light, frequent watering will increase the number of hours each day that grass leaves stay wet. This directly increases the chances of disease while promoting poor airflow, and this can make control more difficult.
Overall, shaded turf is less capable of competing with weeds and pests. On the other hand, some weeds, like crabgrass and goosegrass, also grow poorly in shaded conditions and are less of a problem. This is one reason that early Spring seeding can be effective on shaded lawns.
Shade Management Tips
- Select shade-tolerant cultivars mixed with other high-quality cool-season grasses. A groundcover may be necessary for deeply shaded locations.
- Prune lower tree branches to improve low-angle light and air movement.
- Selectively prune interior tree limbs to improve light penetration (sun flecks) and air flow.
- Cut high and do not allow clippings to accumulate.
- Selectively prune tree roots as you would limbs. Do not remove too many at one time or remove roots that are too large when compared to the diameter of the tree (this benefits the trees as well as turf).
- Reduce traffic on shady areas of the lawn.
- Promptly remove fallen tree leaves, sticks, and clumps of clippings.
- Water deeply and infrequently. Avoid late afternoon and evening irrigation, which promotes disease.
- Minimize nitrogen fertilization during spring and summer and maximize potassium fertilization and supplement with iron for color.
- Apply fungicides, when necessary, to check disease outbreaks.
- Leave an appropriate turf-free zone around trees to improve their growth (create mulch rings; a larger diameter trunk requires a larger mulch ring).
- Keep soil pH neutral. Areas under the drip line of mature trees will be more acidic than the full-sun areas of the lawn.