Zach at Arizona Worm Farm created a “forest of fruit trees” that he can pick fruit from every day of the year. In this post, he shares his 4-step permaculture method for how to fertilize fruit trees organically. This method replicates what the trees get in a forest, producing healthy trees with more fruit.
Guest Post by Zach Brooks, Owner of Arizona Worm Farm
One of our goals at the Arizona Worm Farm is to create a “forest of fruit trees” where there is something bearing fruit every day of the year.
Some of the most dense, healthy plant growth on the planet is in forests. Who fertilizes those plants? Mother Nature! What we try to do here on our farm and in our yards is (as much as we possibly can) mimic the aspects of the forest that promote healthy, hearty growth and produce an abundance of fruit.
How do we create a forest environment in the desert?
Let’s start with a definition: In soil biology, detritus is dead organic material. Detritus in the forest typically includes the bodies or fragments of dead organisms and plants and their waste. Detritus typically hosts communities of microorganisms that colonize and decompose it.
Most of us don’t have animals roaming our properties that will poop or die, and few of us have enough trees to shed enough leaves to mimic a forest. In an urban environment, detritus is replaced quite nicely with compost.
To mimic nature and fertilize fruit trees organically, we need:
- The detritus that falls from the trees and plants and animals.
- The living micro and macro-organisms in the soil that convert that detritus to food for our trees.
- A dense covering on the ground to prevent evaporation and erosion while providing a habitat for the living organisms that make this all work.
Before you begin:
A pre-step: first, create a berm (about 6 inches high) at the dripline of your tree. That’s the line where if you sprayed water on your tree, the water would drip. If it is a very young tree, go to where you guess the dripline will be in three years.
4 Simple steps to fertilize fruit trees organically
How do we achieve forest-level success in our desert environment? It is surprisingly easy and consists of four steps.
Step One: Add microbes to feed your fruit trees organically
How to add microbes:
Worm castings or worm castings tea is the best way to add microbes in large numbers. Worm castings (or aerated tea made from the castings) create or join a soil ecosystem already full of bacteria, protozoa, amoeba, fungi, and nematodes.
A teaspoon of good, active garden soil, according to microbial geneticists, contains a billion bacteria, several yards of fungal hyphae, several thousand protozoa, and a few dozen nematodes. By adding worm casts to this equation, you boost the soil ecosystem and help it flourish.
Microbes (which you boost by adding worm castings) are the ultimate organic fertilizer. These microbes are the opposite of chemical pesticides that poison and kill everything in the soil in the name of abundant yields.
How many worm castings to add:
Scientifically, the perfect amount of castings is 5% – too little, and you won’t get the abundance of microbes we are looking for; too much, and you are just wasting money. It is easy to measure 5% when we mix a raised bed mix, but it is harder for a tree.
Our “rule of thumb” is about a cup of worm castings per three feet of tree height. My personal favorite advice is “toss a couple of handfuls.”
How to add the castings:
Spread castings around the base of the tree, right on top of the soil.
If you have access to good aerated worm castings tea (either from someplace like The Arizona Worm Farm that makes it or from your own tea brewer), it can be used instead of castings.
Step Two: Add lots of compost to fertilize fruit trees organically
In urban areas where we don’t get natural detritus, we add compost.
What kind of compost is best for fertilizing fruit trees?
The best compost is the compost you make yourself in your own yard using your own yard waste – it will have the nutrients your trees used to grow initially. The second best is to get a diverse combination of composts from companies that make good compost. Generally, the easiest way to do that is to buy most of your compost from someplace you trust and then add a bag or two of different composts.
How much compost should I use to fertilize my fruit trees?
We recommend one cubic foot of compost per three feet of tree height – but there’s not really such a thing as too much compost. It is safe to fill the water well (that area you created with your berm) with an inch or two of compost all the way out to the dripline.
Step Three: Cover with a thick layer of mulch
Why should I add mulch when feeding my fruit trees?
Mulch is your tree’s best friend, especially in our hot, dry climate. Most importantly, mulch is an awesome habitat for microbes.
Some other benefits of mulch:
- Conserves and extends available water.
- Protects the soil from erosion.
- Suppresses weeds.
- Moderates temperature extremes.
- As mulch slowly decomposes, it adds carbon to your soil.
How much mulch should I use?
We recommend you fill the rest of the water well with mulch. There is almost no such thing as “too much” mulch. Generally, aim to use at least 3-6 inches (7-15cm) of mulch. One foot of mulch is not too much.
Step Four: Water trees deeply to encourage deep roots
For healthy tree growth, we want deep, healthy roots. Shallow watering (usually the result of a tree in a lawn that gets watered a couple of minutes several times a day) will encourage shallow roots. Trees that fall over or have no ability to pull water from deep underground in the summer are the result of shallow roots.
How much water does a fruit tree need?
There is a standard rule arborists like to use: “About 10 gallons per 1 inch of trunk diameter per week”. Trial and observation will help you get it right.
How to water fruit trees:
After fertilizing your fruit trees, fill the water well with water (the mulch will float, but it will stay in place). Water slowly, allowing the water to seep into the soil rather than run off. Aim to water to a depth of at least 2 feet.
Watch your tree. After watering, the tree’s leaves should look healthy and green for anywhere from 7 to 21 days, depending on the outside temperatures and humidity.
When you see a bit of a leaf droop, it is time to water again. If you are uncertain, dig down 10-12 inches and see if the ground is still moist. Water only when it is dry to that depth. This will encourage deep roots, which help stabilize the tree.
How often should you fertilize fruit trees?
The basic rule is three times a year: Valentine’s Day, Labor Day, and Memorial Day. These days are usually recommended because they are the start of the three growing seasons in most places. They are also easy to remember.
The best answer is “when your trees need it.” If you observe your trees, you will start to see the compost and the mulch disappearing. This means it has been converted into food by the microbes. It is time to add more food for the microbes when what was there is mostly gone.
You can add worm castings more frequently and aerated teas as often as monthly. We find more than quarterly is probably not needed. Learn how to make worm castings tea in this blog post.
Do I need to pull back the mulch before I feed the trees again?
No. When you repeat these steps, don’t remove anything (don’t push the mulch aside or move compost). Add the same layers on top of the previous layers. Water and the natural cycles will get the levels straight, and we don’t want to disturb micro or macro-organisms.
Some other things matter – like appropriate placement, proper pruning (less is usually better), monitoring for pests, and adding shade when trees are young. But, if you get the four steps for organically feeding fruit trees consistently correct, you will have happy, healthy trees that reward you with lots of fruit.
Arizona Worm Farm is an excellent place to get all the products needed to feed your fruit tree forest organically. They have worm castings, compost, mulch, and worm castings tea available for purchase and delivery.
If you would like to see the Arizona Worm Farm fruit tree forest in person, they offer free public, guided, and VIP tours during regular business hours. See their website for more information.