Spring is right around the corner, the mulch yards and nurseries are fully stocked and you see the landscapers and your neighbors mulching away. But have you ever questioned what you should know before mulching? Is mulch truly beneficial or can it actually hurt my plants? When is the best time to mulch? And what type of mulch should I use?
In this article we will explain both the benefits and issues of mulch, proper time to mulch, common issues that everyone seems to ignore and how to avoid them, and the various types of mulch. What we will not do in this article is sell a service to you. Arborscapes does not provide mulching as a service, rather this information comes from years of experience and having knowledge and an understanding of what plants need, like and dislike and the issues that Arborscapes frequently sees when common practices are not questioned.
In short, trees, shrubs and plants that are properly mulched have the potential to have 70% more absorbing roots versus areas covered in grass or nothing at all. These roots are critical to having healthy trees and plants as they absorb water, nutrients and oxygen.
(Example of root development under grass versus under mulch)
In a natural setting trees and plants mulch themselves with dead limbs falling and remaining on the ground throughout the year, but the larger mulching occurs in the fall when deciduous trees drop their leaves. Why is this? One of the benefits of mulch is regulating soil temperatures. The longer the soil temperatures stay warm, the longer the trees will actively grow absorbing roots. The dropping of the leaves allows the sun light to penetrate through warming the ground while the leaves, or mulch, act as a blanket holding in that that heat. As homeowners we tend to mulch in the spring, mainly for aesthetic reasons or to suppress weeds but we miss out on one of the big health benefits for our trees and plants. Furthermore, landscape companies frequently have to start mulching in the early spring in order to fit everyone into the schedule. We have seen a number of plants damaged as the fresh mulch releases heat warming the plant and tricking it to think it is spring, only to quickly be refrozen creating a line of brown and burned leaves on the lower portion of the shrub. To avoid this, be mindful of the air temperature, spread the mulch in advance away from the plants to allow it to cool, and more than likely just a thin layer is all that is needed which will reduce the amount of heat being released.
There are many types of mulch available including gravel, shredded tires, pine bark, pine tags and the most common double shredded hard wood. A statement I frequently use is “mimic Mother Nature”. Again trees and plants naturally mulch themselves and each other by dropping dead limbs and shedding leaves. However, as home owners, landscape companies and commercial property managers we generally do not find that fitting or aesthetically pleasing and so we regularly clean them up and remove them from the site. What’s important when choosing your mulch is to have something that breaks down over time providing the benefits described in this article. Although shredded leaves is most ideal, at least in my opinion, the double shredded hardwood is the most common, looks the best, and will still be beneficial to your trees and plants. You may also consider putting down a light layer of shredded leaves or compost followed by a light layer of the hardwood mulch.
A very big issue that we see at Arborscapes is over mulching, either putting down too much mulch or doing it too frequently. If we refer back to the idea of mimicking Mother Nature and how trees and plants mulch themselves and each other we notice that the mulch breaks down at the same rate as it is reapplied. You do not see the levels of leaves continuously increasing in the woods. A simple search on the internet will tell you anywhere from 2-4 inches, but it is important to understand that this is not a per year recommendation but to maintain a layer of that amount. Roots grow where there is the proper amount of oxygen and water. When layers of mulch are too deep the fine absorbing roots start growing closer to the soil. Once temperatures increase in the summer and rain becomes more scarce this layer dries out quickly and these roots die.
Another issue with applying the mulch too deep is the accumulation around the trunk. A properly mulched or planted tree will show the flare at the base, where the trunk meets the roots. Build up in this area can create many problems for your trees and plants such as decay of the base, or encouragement of roots to grow towards the surface. Surface roots are more susceptible to drying out and dying or to girdling/chocking the trunk of the tree. This is an issue with 95% of the trees and plants we see.
So getting to the point of how much mulch or how deep to mulch, if this is a new bed apply 2-3 inches, and if this is an annual application, a light layer of less than 2 inches will provide the beauty your looking for without building up over time.
One of the most common things we hear at Arborscapes is that the trees are killing my grass and taking all of the water. Trees and grass were never meant to cohabitate. Think about this, when was the last time you saw a think lawn in the woods? Think of this as more or less a boxing match between the two. Most of the time the tree wins the fight, but not without taking some hits itself. This “fight” can be extremely stressful to the tree making it more susceptible to insect or disease issues. At Arborscapes we remove a lot of dead trees each year from the lawn area as a result of the annual battle between the trees and the grass. Consider ending this fight by mulching around your trees, ideally to drip line, or edge of the branches. I know this may not be feasible, so mulch as far out as you are willing. Your trees will thank you and a nice bed with smaller plants throughout will look much better than an area of grass that does not look as nice as the rest of the lawn.
Another great benefit of mulching is that it can help absorb and maintain moisture in the soil. This is extremely beneficial for the absorbing roots and can reduce the need and amount of irrigation required. But mulch can also repel water or become hydrophobic. This generally occurs in the heat of the summer when the mulch dries out and forms a hard crust on the surface. Obviously, this is the worst time of year for this to occur since the roots of your trees and plants are likely in desperate need of water. To help avoid this, make sure you or your landscape contractor breaks up the surface of the mulch with a hard rake prior to putting down new mulch. When noticed during the summer make sure you again break up this layer so the water can percolate through to the roots of your trees and plants.
Have you ever noticed how much easier it is to dig a hole in a mulch bed vs. out in the lawn? There are a few reasons for this but ultimately it comes down to more poor space and a more oxygenated looser soil. This is basically the equivalent of aerating your lawn. As mulch breaks down to fine organic matter it works its way down into the soil improving the health along the way. In addition, this organic matter can be extremely beneficial to microorganisms in the soil that are beneficial to your trees and plants. Its important to note that there are different microorganisms for trees and plants vs. grass and lawns. Another reason it is beneficial to remove the grass and mulch around your trees.
A quick note on these weed barriers. In my opinion these fabrics are not needed, do not provide long term benefits and can reduce the amount of water and oxygen that passes through to the roots of your trees or shrubs.
Healthy soils equal healthy plants and properly mulching is a large part of improving and maintaining the health of your soils. If you have questions about good mulching practice, let us know! Thank you as always for your trust, and happy growing this season!