Does Tree And Shrub Fertilizer Actually Work?

Everything You Need to Know About Tree and Shrub Fertilizer

Most of us are familiar with plant fertilizer. You just sprinkle some of the colorful granules on your lawn and next thing you know, your grass is bright green and thicker than the hair on your head. Right? Well, it’s not always that simple! Truthfully, the majority of homeowners don’t know what they’re doing when it comes to fertilizer — especially when it comes to trees and shrubs. Whether you apply too much or too little, use it at the wrong time, or assume all fertilizing products are the same, there’s a lot to learn when it comes to tree and shrub fertilizer. To cut to the chase — fertilizer does work, not only for your lawn but for trees and shrubs as well. You just need to know how to properly use it to your advantage, because it’s not as easy and straightforward as you might think.

What is fertilizer?

Tree and shrub fertilizer is almost always mistaken as plant food. However, plants technically make their own food through photosynthesis. You could say fertilizer is what gives them the energy they need to make their own food. Better yet, think of fertilizer as a multivitamin rather than food! There are three main nutrients in fertilizer: nitrogen (N), phosphorus (P), and potassium (K). Some pre-made fertilizers also include added nutrients for even more benefits like calcium, magnesium, and sulfur.

Types of fertilizers

Fertilizers come in two options: synthetic and natural. Synthetic fertilizers can be fast and slow-release. Fast-release fertilizers are usually water-soluble so they move quickly through the plant's roots system. Sometimes they move too quickly, and therefore don’t provide enough nutrients for the roots before it’s washed away or fully dissolved. On the other hand, slow-release fertilizer is considered the ideal option between the two because it works by slowly releasing nutrients over an extended period of time. Natural fertilizers usually come in the form of compost or manure and are a great DIY solution if you’re an organic or eco-friendly gardener. Unlike its counterpart, natural fertilizer also provides minor nutrients like iron and zinc. Additionally, natural fertilizer improves the soil’s structure by adding organic material to the soil, rather than the dissolvable granules of synthetic fertilizer. The one downfall to natural fertilizer? It contains less nutrients per volume, so you’ll have to apply a lot more to get the same effect as a smaller dose of the synthetic variety.

Find out what type of fertilizer to use by testing soil pH

Fertilizers come in a variety of different formulas, which is where homeowners typically make the biggest mistake in assuming all fertilizers do the same thing. In order to know what type of fertilizer to use, you first need to test your soil to see what it’s deficient in! Don’t assume you know where your soil is lacking just by looking at your plants. Although some symptoms are obvious, like leaf drop, many symptoms can have multiple causes making it impossible to guess what nutrients are needed. An actual soil test will be able to determine exactly what’s missing, without the guesswork and possibility of accidentally making things worse for your trees or shrubs. There are many pH testing kits available and DIY tricks you can do at home, but these aren’t the most accurate methods for testing. Fortunately, we can do the pH testing for you as part of our lawn care packages.

How to apply tree and shrub fertilizer

Now that you’ve tested your soil's pH level and know exactly what nutrients it's lacking, you can apply the correct fertilizer! Be aware that you can’t use all lawn fertilizers on your trees and shrubs. For example, if a synthetic fertilizer includes a weed killer, it can damage tree and shrub roots. On the other hand, natural fertilizer won’t harm them because it doesn’t contain any herbicides. Another important note: fertilizer isn’t a cure for sick or dying plants. Sometimes people will notice their tree or shrub is dying and think all it needs is a good dose of fertilizer to fix whatever's wrong, but that’s not what it’s used for! Remember, fertilizer is not food. Before applying tree and shrub fertilizer, follow these three guidelines:

Are you noticing growth?

Look at your shrubs and trees for signs of poor growth. This includes pale-colored leaves and leaf sizes that are smaller than normal. Poor growth can be a sign of malnourishment. Again, a soil test will confirm this!

How old is the tree or shrub?

If the tree or shrub is older the fertilizer will be less effective. Fertilizer application is generally only recommended for younger plants or newly transplanted trees and shrubs. For transplanting, the fertilizer can speed up the plant's growth so it will fill into the new allotted space.

Has the area already been fertilized?

Similarly, tree and shrub fertilizer works best on areas that haven’t been fertilized yet. If you’ve already applied a general fertilizer (that doesn’t contain weed killer) throughout your lawn, this should be enough to keep your plants healthy. But if you haven’t, we recommend a healthy dose of tree or shrub-specific fertilizer. For best results, aerate your lawn before applying fertilizer so the nutrients can better reach the grass roots!

How to Get Healthy Trees and Shrubs the Killingsworth Way

In short, the answer is yes! Tree and shrub fertilizer actually works. But it will only work if you understand why, when, and how to use fertilizer. Having said this, trees and shrubs need more than just vitamins to be happy and healthy. They also need to be protected from weeds, pests, flooding, and much more. Schedule a lawn care consultation or service today.

This blog post was originally posted in April of 2018 and was refreshed in April of 2020.

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