We talked to a lot of people this weekend at the Durango Home and Ranch show. Two topics stuck out, why are my Aspen trees dying and what to do about the intense drought that we are facing. The reasons why Aspen's struggle as a landscape tree and why they are on the City of Durango's list of trees NOT to plant is the subject of another blog post / rant. The issue of the drought, however, is something that is and will continue to affect all of us in the southwest. Knowing what trees you have and what their water requirements are is the first step. Native species like Ponderosa Pine, Pinon Pine, and Juniper need little to no supplemental watering as they are well adapted to deal with drought. Trees such as Weeping and Navajo Willow as well as the few common species of Cottonwood in our area require more water. As a general rule deciduous trees require more watering as their leaves are more susceptible to evaporation and heat than their needled cousins with more water efficient adaptions. So the question is : How do i make sure my trees are getting the water they need, without spending a fortune? A simple answer is, Mulch.
The reason that mulch is such a good thing is that it retains water, keeps the soil underneath and more consistent temperature, and breaks down into the soil, thus improving soil quality. There are many ways to efficiently deliver water to your trees and their root zones, ie. drip irrigation systems. However, mulch is the easiest and most cost effective way to make the most out of any water that falls naturally as well as supplemental water applied by you. Ideally mulch would cover an area equal to the drip line of your tree, meaning as far out as the widest branches. Many times this isn't a feasible option if you have a large tree and do not want your entire yard to be mulch. Keep in mind that this is the ideal situation and concessions can be made to suit your landscape design. The layer of mulch should never exceed 4 inches as that would reduce the soil - oxygen interaction that roots need to thrive. Furthermore, mulch should not be touching the trunk of the tree as that could lead to too much moisture on the trunk which may breed certain molds or fungi. There are many types of mulch available that serve those purposes, but with different levels of effectiveness.
The best mulch that you can put down to accomplish the three tasks above is general arborist mulch. This is all of the byproduct of pruning and removal operations by local arborist companies such as Deep Roots Tree Care. This mulch is generally available from your local nurseries as well as directly from the companies themselves. We do sell mulch, so I realize that my opinion here may seem biased. However, arborist mulch contains more organic material such as leaves that speed up the composting process of the mulch, causing it to break down and incorporate into your soil faster. While there is some nitrogen leeching that occurs during this process, it is returned to the soil as the mulch composts and has not been shown to have any dramatic affects on the growth of trees. Arborist mulch is usually the cheapest mulch available as well. Aesthetically it is not always uniform in size of chip or in color, so if those are of major concern a more expensive prepared mulch might be a better option. We see a lot of bark mulches made from ceder bark or pine bark. These are prized by landscapers for their uniform good looks as well as good smell. Tree bark is made of lignin, and its job is to keep moisture and other bad things away from the the sapwood and heartwood of the tree. Mulch made from tree bark does not break down as fast as arborist mulch so it is possible to wait longer before the need for re-application. However, during this time it gets matted down and, because its bark, creates a moisture barrier to the ground. Instead of soaking up water it sheds water. If you choose to use bark mulch is it imperative to "fluff" it to prevent this from happening. Talk to your local arborist or your local nurseries and decide which mulch works best for you and your specific needs.
So get out there, spread some mulch and spread the word!