Though a favorite of many gardeners, evergreen trees have a reputation for changing soil acidity, making them less suitable to grow in a backyard where you want full greenery. While evergreens do typically live in acidic soil, are they the cause of it? Do evergreens make the soil more acidic?
Evergreens do not make the soil more acidic unless they have been in that location for a very long time. The soil that evergreens often grow in is typically acidic even before the trees grow. In other words, the soil being acidic is a cause rather than an effect of evergreen growth.
When it comes to working with evergreen trees, understanding how these plants interact with soil acidity is important in ensuring healthy plant growth. Read on to learn more about evergreens and soil acidity, what is pH and how to control it, how evergreens impact soil pH, and the effects of growing evergreens in your backyard.
Soil pH Explained
To understand how evergreens impact soil acidity, it’s important to first understand what acidity is and how it is measured.
If you’ve ever taken a science class, or watched certain TV shows, you probably know something about some of the impacts acidity has on different substances. We know, for example, that acid can break down many materials, but why this happens is a mystery to most of us.
The term acidity refers to the quality of having a low pH. pH is the unit of measurement used to track the acidity of a substance and refers to the concentration of hydrogen ions in the substance.
On their part, hydrogen ions are a type of hydrogen atom that carries a slight positive charge. When particles bond, hydrogen often “gives up” an electron to another atom in order for the two to bind together. When this occurs, the hydrogen atom loses its negative charge, making it positive.
Since these hydrogen ions are so small and so easy to force interaction with, they often interact with other substances when mixed together. This is what causes highly acidic substances to break down other materials.
If a substance has a high concentration of these hydrogen ions, the substance is termed acidic. If it has a lower concentration of hydrogen ions, it is basic.
Important to note, however, is that acidity only really exists in aqueous solutions (fluids that have water in them). While a solid object can impact the acidity of an aqueous solution, the solution is what is actually the acid or base. Soil, because it contains water, might be more acidic or less acidic based on the number of hydrogen ions in the water.
Evergreens Don’t Affect Soil Acidity
Despite the commonality of the claim that evergreens increase soil pH, this is actually not true.
Evergreen plants grow in acidic soil, they don’t really cause the soil to change its acidity levels. In other words, because the soil is acidic, evergreens grow. Evergreen growth is thus an effect of having acidic soil, not a cause.
Also important to note is that evergreens like acidic soil not because it has a higher concentration of hydrogen ions. In fact, this has a very minimal impact on the growth of evergreen trees.
Evergreens like acidic soil because of the nutrients that most commonly exist within the soil. The plants love to use small amounts of manganese and iron in order to grow strong. These chemicals often increase the concentration of hydrogen ions.
Another common misunderstanding is that evergreens, such as pine trees, acidify the soil through their needles.
Pine needles are highly acidic when they fall off trees. In fact, if these needles were to dissolve upon contact with the ground, they would raise the soil acidity significantly. However, because the needles take a long time to decompose, their acidity also depletes, making the impact rather insignificant.
Evergreens are unlikely to raise soil acidity by dropping pine needles, and this process would take years and millions of needles to make a noticeable difference.
Effects of Evergreens in Backyards
Though the effect evergreens have on soil pH might not be that significant, this doesn’t mean they don’t impact other plants growing in the same area. Nature is one massive life cycle, where one plant or animal’s actions impact other organisms. The sheer fact that you have evergreens growing in your backyard will impact your other plants.
Let’s take a deeper look at some of the bigger impacts evergreens have on gardens.
Providing Organic Material
One of the most important roles evergreen trees play in the ecosystem is contributing large amounts of organic material for the surrounding area to thrive. Unlike deciduous trees, evergreens don’t drop all their pine needles during one season—the needles fall throughout the year. This provides a great source of food for microorganisms, which then break down the needles into nutrients for other plants.
Impacting Water Usage
Another role evergreens play in your backyard’s ecosystem is competing for resources with other plants.
Evergreens consume equal amounts of nutrients as other plants but often use a lot of water. During dry spells, you might notice that plants around pine trees tend to die because the deep root systems of the evergreens suck up most of the water. This competition with other plants has a huge impact on which plants succeed in which environments.
Providing a Hospitable Level of Light
Plants need sunlight to create energy through the process of photosynthesis. However, if they are exposed to too much light, they can overproduce energy and die from overheating and lack of water.
Many evergreens are quick growing and often filter the amount of sunlight other plants receive. In most cases, evergreen trees will not prevent plants from getting light, but they ensure that they don’t get too much of it.
Controlling Soil pH in Your Backyard
Now that we understand soil pH, the impact evergreens have on soil pH, and how evergreens impact your plants, you might be wondering how you can impact soil pH.
As noted earlier, many plants don’t choose their location because of the acidity, but rather due to the nutrients available. Some plants do choose, however, not to grow because of the soil’s acidity.
In such cases, controlling soil pH is necessary so as to help encourage a biodiverse backyard. The best way to impact soil pH is to add supplements. These help to neutralize pH levels or intensify them.
Acids and bases automatically destroy one another. This means that if you have soil that is too acidic, pouring a base into the soil will break down some of the acids and bring the pH closer to neutral.
Of course, your objectives will determine which supplement you should add. For instance, if you need to make the soil more acidic, add sulfur, ammonium sulfate, or acidic fertilizer. Conversely, if you need to make the soil more basic, add lime, ash, or another carbon-heavy material.
Important to note, however, is that controlling soil acidity is not an exact science. Soil supplements can change the general makeup and acidity of the soil. However, you might need to apply them multiple times or in different amounts to achieve your goals.
Always read the manufacturer’s directions and consult expert help if needed to effectively doctor your soil.
Final Thoughts
While they are certainly acidic plants, evergreen trees don’t contribute to the acidity of the soil. Evergreens grow in acidic soil, rather than making soil turn acidic. Though over a long period of time evergreens might be able to change soil pH, this change would be marginal at best.
Evergreens do play many other important roles in regulating your garden, including providing nutrients for other plants, regulating resource availability, and protecting plants from extreme conditions. You can’t really use evergreens to regulate soil pH, but you can use other suitable materials to do this more effectively.
