Along with it being a good practice to keep the leaves as a source of nutrients for the soil, and microbial life care must be taken so that the leaves don’t sit too long without being mulched. Recently we had one of, if not the most, damaging snow storms in CU's history related to landscape tree and shrub damage. The reason this happened is because with such a large and early storm, the majority of the trees on campus still had their full canopies to hold onto the snow. Being so early in the fall, the turf had not hardened off for the winter yet either. We spent two solid weeks with our entire staff working non-stop to try and make the campus safe from falling tree branches. Just prior to the storm the leaves were starting to fall, and the heavy snow brought down not only large amounts of trees, but also defoliated the majority of the leaves, leaving extremely thick layers of debris on the still lush turf. Once we started to get a handle on the safety aspect of campus and began to make progress on the clean-up, I started to take a look at the turfgrass under these thick leaves.
As you can see in the above picture the turf has a yellow look to it; this is called chlorosis. It is evident when the plant is unable to make and sustain chlorophyll due to a lack of sunlight. Since the plant is still in a stage of growing, it is still in need of nutrients and with the thick coating of leaves, was unable to produce the amount of chlorophyll needed. This situation, if left unchecked, will cause loss of plants. Depending on how dense the cover it can kill off an entire area and when the spring comes around the turf is all dead in that location. The other scenario you can be faced with in this situation is lack of oxygen and abundance of moisture which can cause turf disease, again resulting in loss of plant material. So obviously we had to make some adjustments to our manpower and clean-up operation. Once the campus was in a safe condition we pulled a few staff member to start the process of leaf mulching.If you were to see this in person the turf will almost have a look of being rotten. Like any other landscape, debris in the early stage of decomposition is very limp, very damp, and over all just not healthy. Luckily this situation though is very treatable just by simply blowing the leaves off and allowing the affected area to get some sun and air. The condition will not be sustained and everything will return to normal.
You can see in the above picture that the leaf blades are yellow and in some cases brown. The blades that are more of the brown color are the plants that are further along in the process and are starting to die off. Some of those individual plants may or may not come back around. I believe that we caught the situation early enough and made corrections so that we will not have any noticeable damage from this event.
So again, leaves are great for your home lawns and gardens but you need to follow the classic idea that there is such a thing as "to much of a good thing." :-)