Myth: Oak Leaves are Killing My Lawn
This persistent myth is hard to debunk. Common scenario is that a home owner has a landscape with young oak trees. Years go by and the lawn looks great. Then as the tree matures and becomes 50’ tall the lawn develops random weak spots. These weak spots are caused by a thick mat of roots. These weak spots are natural gathering places for Oak Leaves. The homeowner sees leaves covering a bare spot in the lawn and assumes the leaves killed the lawn. But you can’t see the roots below ground, you only see the leaves. So leaves get blamed for killing the lawn.
Biology of Oak Leaves
A fallen Oak leaf retains its shape long after it has fallen from the tree because Oak leaves have a durable outer shell similar to a crab shell that does not quickly break down. It is a hollow empty shell of a leaf and has no negative impact on your lawn.
Of course if the leaves are several inches deep and remain on the lawn for weeks, then you could suffocate the lawn – but I have never seen that happen except where someone raked leaves into a pile. And when the pile of leaves was removed the lawn quickly recovered.
Save Yourself Some Work and Don't Rake the leaves
Raking oak leaves damages the lawn. St Augustine is the least trafficable turf grass - in other words, it is damaged easily by traffic or a leaf rake. Raking leaves in the fall damages the leaf during the semi dormant period - a time when recovery from such stress could take months.
The better way is to mulch the leaves with a good mulching mower and turn them into compost for the lawn to use.
Composting of Oak Leaves is Beneficial – Just Add Water
Two critical environmental conditions must exist to compost Oak leaves; A tall canopy height of the St Augustine lawn and water. Both conditions are quite easy to achieve – mow as high as the mower will go and water as often as law permits (even during cool weather). Do not be tempted to mow low to mulch more leaves – be satisfied they have fallen into the canopy. Trust me, the leaves will obey the law of gravity and continue to fall deeper into the canopy where biological forces will turn them into mush.
Once the Oak leaves are composted they become beneficial – not harmful – to your lawn. Below the lawn canopy, next to the soil is a very biologically active area of your lawn. It is an area of active composting. Leaves and all types of lawn debris – including dust, pollen and other pollutants - are being recycled into nutrients for the soil and plants. The Oak leaves feed the composting microbes with a steady supply of organic matter and minerals (mainly Carbon).
The Natural Processing of Oak Leaves - No Raking/Bagging Required: The natural organic method (and perhaps the easiest) for processing of Oak leaves in St Augustine lawns is to mow your lawn with a mulching mower. The mulching action shatters the oak leaves and allows them to fall into the turf canopy. Once inside the canopy, the oak leaves are composted by natural processes to provide nutrients, minerals and organic matter for soil microbes and the lawn.