Grass grown in shade will often deteriorate, becoming sparse or of poor quality if it does not receive enough sunlight. Choosing a seed mix that is more tolerant of shade can help.
Problems with shaded lawns
Most turf grasses require four to six hours of full sun each day. Without this there is a reduction in photosynthesis and the turf will deteriorate, be less resilient and more prone to disease.
Turf will rarely do well under trees (left) with dense canopies, such as oak, which block out nearly 95 percent of summer sunlight. Their feeder roots compete for water and nutrients, and drip from the canopy is also damaging.
Remedies for deteriorating grass
Selecting shade-tolerant grass mixes (left) is the most important factor in growing turf successfully in shade. Fescues are better at coping with shade, drought and poor nutrient levels. In damper soils, opt for a mix with more bents. However, even grasses that are claimed to be shade tolerant need some light to survive.
Lawns showing signs of deterioration can be ‘overseeded’ (right) with a shade-tolerant mix. This is best done in early September. However, if the soil is compacted, of low fertility and heavily infested with moss it may be better to replace it. For many areas, it may be more practical to use a ground covering other than turf.
Shade modification
Consider removing selected trees to improve light levels or prune trees to increase light. It is also beneficial to leave a turf-free zone of 1m (39in) around trees. Plant species that cast light shade such as Betula, Gleditsia and Robinia.
Cultural practices
Even shade-tolerant grasses prefer sunny locations, so lawns grown in shade will require careful management:
Mowing: in shade, cut lawns less frequently and no lower than 6cm (2.5in) and preferably 7.5–9cm (3–3.5in). Always remove the clippings.
Watering: if lawns beneath trees require watering, irrigate heavily and infrequently to encourage trees to root deeply.
Feeding: lawns in shade are best fed in autumn, just prior to leaf fall. They can also be fed in early spring about one month before trees begin to leaf. Use half the rate of nitrogen applied to turf in full sun. High-potassium (K) feeds are particularly beneficial to grass growing in shade.
Moss control: moss will tend to out-compete turf grasses in cool, moist, shaded situations.
Alternatives
In areas of dense shade, such as that cast by buildings, it is more appropriate to consider alternatives such as decorative mulches or shade-tolerant ground cover.
Tony Dickerson