Yellow leaves are a big source of worry for many fruit tree owners. So much so that we’ve done an entire blog on it here.
We’re always banging on about healthy soil being the foundation of your entire food growing system. It’s one of the main things you should always be working to build and improve.
So it won’t surprise you to hear that some (but not all) causes of yellow leaves can be fixed by improving the soil.
Healthy soil can help prevent yellow leaves
There are lots of techniques available to help you improve the soil, but one of the common questions we’re asked, is “how?”.
Adding aged chicken manure, compost, and worm castings are just a few (and we’re big fans of them all). Planting a diverse understorey is another really useful technique for rapid soil improvement, and you can learn more about that here.
A slightly more advanced technique is brewing your own compost tea. We brew it on a big scale (as you can see in the photo below), but it’s also easy to make on a home garden scale.
What is compost tea?
It’s probably easiest to start with what it’s NOT, which is compost extract.
Compost extract is made by putting compost in water and swishing it around or leaving it to soak. You can do a similar thing with weeds to make a weed tea or weed extract.
This technique is extracting some of the nutrients from the source material into a solution, along with some of the microbes. It’s a fantastic thing to do, and makes spreading the nutrients around your garden really easy.
However, this method doesn’t increase the number of microbes in the brew. That’s the point of compost tea.
To brew compost tea you start with a small amount of something that’s rich in microbes. This might be good quality (preferably home-made) compost, or worm castings if you have a worm farm.
Leaf litter from under a mature gum tree is also perfect as a source material because it’s highly fungal. Use the broken-down layer under the top layer of litter.
The source material is placed into water and agitated to knock the microbes off.
Then add microbe food and oxygen for 24-48 hours and voila! A small number of healthy microbes will turn into a huge number in a very short time.
The main types of microbes you’ll be brewing including bacteria, fungi, nematodes, and protozoa. The microbes breed like…well, like microbes (that is, REALLY fast when conditions are right).
Making compost tea on a home scale
On the farm we always make 1,000 litres at a time, but you can make much smaller batches at home.
There are a couple of drawbacks about making compost tea. It’s a bit fiddly to make and needs some specialised equipment. However, everything you need is readily available and fairly cheap, and you only have to set up your brewer once. We explain how to do it in this course (including plans for making a home-sized brewer).
How to use compost tea
Once a batch is finished, we always check to make sure we’ve brewed the right kind of microbes. We also like to make sure there are actually microbes present and we haven’t just made a nice brew of brown water. That’s not necessary for a home-brew situation, as long as you follow the guidelines.
Then we just put the tea on the soil under our fruit trees and let the microbes go to work.
The other thing to consider is that microbes are a bit like Goldilocks. They won’t be happy in the soil if the temperature is too cold or too hot, so wait for the weather to warm up before you get started, and then avoid brewing tea in a heat wave.
If the yellow leaves on your fruit trees are caused by nutritional deficiency or poor soil, compost tea is definitely part of the fix. But it won’t happen overnight!
Compost tea is not a “quick-fix” solution. It’s part of a long-term strategy that can take a couple of years to have a positive impact.
The best way to think of compost tea is as another tool in your healthy soil toolbox.