It is important to understand that proper tree care starts when you select a tree. And what you do to your tree in its first few years of life bears a long-lasting effect on its shape, strength, and even its lifespan. Other than watering, there’s arguably nothing better you could do to help your new tree get established than add a layer of mulch. Mulching your trees serves several key functions.
What qualifies as mulch to begin with? It is more or less any organic matter, from wood chips, to compost, to straw. Carbon is nature’s ‘sponge’, and generally, organic matter that is brown (dry leaves, twigs, wood chips, straw) is primarily carboniferous and can hold available moisture to feed growing tree roots.
For humans, nutrients are either fat or water-soluble, but trees get all that they need from water. Mulches both hold moisture for trees’ use and are arguably the best way to fertilize a young tree by providing slow-release nutrition that leaches down to the roots below with rain.
Also, mulching your trees moderate temperature to help contribute to vigorous root growth. The vast majority of stabilizing tree roots reside in top 3-4 inch of soil where they have access to oxygen, whereas only a small percentage dig deep down as many might assume. For this reason, our objective as tree planters is to encourage root growth horizontally. Apparently, tree roots are ‘lazy’ and they tend to grow where conditions are good. Young roots will happily grow into loose soil, but they have a harder time punching through the hard-packed clay we often find in urban environments. They’ll grow even more enthusiastically into loose soil that is mist and held to a moderate temperature.
Withthis background, we’ve learned that mulch retains moisture, but another way that it contributes to creating good conditions for root growth is by helping maintain temperatures conducive to root growth. Unlike the tree canopy, roots can grow whenever the conditions are right. The primary ingredients for those conditions are adequate moisture and moderate soil temperatures. When a tree is well-mulched, the soil around its roots is slightly warmer during winter and slightly cooler during summer. This happens naturally in a forest as twigs and leaves constantly shower the forest floor, so we are simply recreating what young trees find in a more natural setting to ensure they thrive in years to come.