Deep Root Fertilization: Your Complete Guide

Deep Root Fertilization: Your Complete Guide

check tree healthDeep root fertilization might just be the best way to fertilize trees.

Not sure what that is, how it works, and whether or not your trees and shrubs need it? Strap in. We’ll cover all the basics.

Why do I need to fertilize my trees?

First things first—let’s talk about why your trees and shrubs may need deep root fertilization.

The trees on your property look a lot like their self-sufficient, forest-dwelling cousins, but there’s one big difference: their environment.

Wild trees don’t survive to maturity unless they’ve taken root in a place that meets all their needs. Compare that to trees on developed land, which are often transplanted, subjected to landscape changes, or forced to compete for nutrients with grass.

If the trees (and shrubs!) on your property weren’t carefully selected for the site, there’s a good chance they’re not getting all the nutrients they need.

This makes for trees that grow slower, are more susceptible to insects and disease, and have shorter life spans—not exactly ideal for your yard. Keep a special eye out for signs that your plants are struggling if they fall into any of these categories:

  • You live in a city or suburb
  • Your trees are established, but came from a nursery
  • You have trees and shrubs that aren’t native to your area
  • You remove all leaf litter before it has a chance to break down

How to tell when a tree needs fertilization

An expert will be able to assess your tree’s needs best, but here are a few of the warning signs that you can check for on your own.

Yellowing or off-color leaves.  Struggling trees often show signs of stress in their leaves. Trees that naturally have colored or patterned leaves don’t count, of course

New shoot growth is under 6 inches. Happy trees grow 6-plus inches a year. When growth falls under that benchmark, we recommend fertilization. If the tree has started to encroach on a house, deck, or patio, you might need a treatment that will safely slow the tree’s growth while promoting root grown and maintaining health. We call our blend ArborBalance and find it works well even in older and declining trees.

Visible dieback. Insect attack and disease can also contribute to dieback—make sure to either rule those out or treat them first.

That being said, not every landscaped tree is going to need fertilization—we’ll get into this later.

What’s deep root fertilization and how does it work?

tree root fertilizationDeep root tree fertilization is what we call the process of fertilizing trees and shrubs via a liquid fertilizer soil injection. It’s the fastest way to get nutrients to the plant and has the added benefit of aerating the soil.

First, you (or your arborist) need to assess the plant’s needs. This is where soil tests come in handy—they can help give you an idea of what nutrients your soil needs. Though your arborist will likely adjust the fertilizer blend to suit the soil, the 3 most commonly needed elements are:

  • Nitrogen
  • Phosphorus
  • Potassium

From there, your arborist will use specialized tree injection equipment to inject the liquid tree fertilizer about 6-8 inches beneath the surface. They’ll then continue the process, placing injection sites 2 to 3 feet apart in a grid pattern underneath the tree’s canopy and slightly beyond.

When should I fertilize my trees?

Our arborists generally recommend deep root fertilization once or twice a year in the spring or fall.

Both times have their benefits. During spring, plants are gearing up for a season’s worth of growth, and fertilization provides a nice boost of nutrients. During the fall, trees take in the extra nutrients for their winter dormant period.

Fertilizing annually is especially important to encourage growth in small trees, though old, established trees can sometimes skip a year.

When deep root fertilization isn’t appropriate

It’s worth noting that fertilization isn’t right for every tree.

In the summer, the winter, and when the tree is recovering from drought and certain health issues, we don’t typically recommend fertilization. Newly planted trees, meanwhile, don’t benefit very much from fertilization—they need time to establish their roots before they enter a period of more rapid growth.

When we can’t fertilize a tree that is stressed or struggling, or else want to encourage root growth over trunk and branch growth, we usually recommend a biostimulant.

This kind of treatment promotes fine root development, improves soil structure, and increases drought and stress tolerance. We call our own custom blend ArborKelp®, and apply it the same way we would a fertilizer. This is a great option to look into if you’re concerned about tree stability and recovery, as it can be applied multiple times a year.

Do I need to use a tree service?

Yes and no.

Only a tree service expert will have the equipment needed to preform deep root tree fertilization.

However, if you’re not ready to call in the experts yet, you can always try surface fertilization. This process takes more time and effort, as it’s dependent on rainfall to move the nutrients underground to the tree roots. It won’t work well on turf or sloped land, though, and if you have more than a couple trees on your property, it can get expensive.

Your best option is to get in touch with a local arborist for advice. They’ll be able to diagnose your trees and help you figure out which treatment will get the results you’re hoping for.

We offer free consultations! Get in touch to see if there’s a SavATree in your area here.