Throughout our three generations tending to the lawn care of Calgary’s commercial and residential property owners and managers, we here at Mirage Landscaping have come across more than a few tough questions.
One of the queries we hear often is, “Why won’t grass grow under my spruce tree?” and arises from the rather obvious fact that the space beneath such trees in most places is usually comprised of bare dirt and needles.
The conventional wisdom as to why grass doesn’t grow beneath spruce trees varies, but the truth is that it can be done with a little work and effort. Our lawn care and landscaping professionals can help explain how to achieve this look to anyone who wishes.
Some research says that pines and spruces drop needles that change the local pH of the soil, which then discourages the development of undergrowth. Other theories say that these trees are voracious resource competitors, drawing off soil moisture and nutrients to “starve” other plant life.
While it is true that conifers of all types thrive in more acidic soils, and that the acidity of such soils necessarily permeates every part of the tree during its lifetime, it is not necessarily true that fallen needles constitute an “acid dump” upon the soil underneath the tree.
From the moment a needle falls from an evergreen it starts oxidizing, gradually turning from a vibrant green to a spent brown. This is because of molecular breakdown caused by exposure to environmental oxygen as well as micro-organisms, both of which change the needle’s composition, leading to eventual decomposition. During their time spent feeding the microscopic world, needles lose their inherent acidity. So, spruces and pines do not radically alter soil acidity.
While dead needles are not acid factories, they do take a long time to totally break down and remain very water repellant. Left on the ground, dead needles are an effective physical barrier to growth. If you want a lush lawn to carry through to underneath your spruce trees you must rake regularly.
Grasses, like every other plant, require acceptable growing conditions to thrive. After raking, ensure that grass will grow in evenly by doing the following:
Thin out. Even shade-loving grasses will not thrive beneath a tight knot of mature evergreens that are casting deep shadows all day. Thin out the branches to create dappled sunlight underneath for most of the day. By thinning out your trees, you will also reduce their “rain shadow” effect, allowing rainfall to actually make it to grasses growing beneath.
Lower acidity. Mix in a layer of lower-acidity top soil into the top couple inches of dirt underneath the tree. This will not only provide better growing conditions, it will also help balance the nutritional inputs that allow both grass and evergreens to thrive together.
Seed! Throw down a nice even layer of high-quality grass seed on to your newly-mixed topsoil. Rake lightly, and then add another layer.
Water. New seed requires a lot of water, but since you are trying to grow grass in a naturally shady spot, it can be very easy to over-do it. Watch carefully to ensure you aren’t flooding anywhere when watering, and allow the area to dry out fairly thoroughly before watering again.
Mirage Landscaping of Calgary has generations of experience serving both commercial and residential clients. We offer free quotes on any size job.