Are the leaves that fall from your fruit trees in autumn a bonus for your garden, or a problem? We’re often asked if it’s OK to let them rot on the ground, or can they cause disease?
Should you be picking all the leaves up and doing something with them? And if so, what?
People often ask these questions because they’re noticing yellow leaves on their trees and wondering if they’re carrying a disease. There are 4 main reasons for yellow leaves. In autumn it’s usually due to the natural process of going into dormancy.
There’s often not a simple answer to these questions. In fact, issues like this need to be decided by comparing the costs of taking action (in time, money, or effort) against the benefits.
Plus, consider what you’ll do with the leaves if you collect them, and factor that into the equation. If they can be composted or be fed to animals, and therefore returned to the soil, great! That would be providing a positive result for your hard work.
But it’s a very different equation if they’re filling up your greenwaste bin, being burned, or—horror of horrors—going into landfill! In that case, you’re turning a potential resource into a climate-changing problem.
The best-case scenario is to return the lovely organic matter and nutrient in leaves to the soil. However, if there are fungal spores on the leaves which may create disease in the tree next season, there may be a potential risk. Two fungal diseases that can overwinter on leaves are Black Spot and Blossom Blight.
So, how to decide what to do?
The rule of thumb is that it’s best to let the leaves rot under the trees as long as they break down quickly. They should disappear within a couple of months, and certainly before next spring.
This is the least amount of work for you, for the greatest benefit for your soil. However, it does rely on you having reasonably healthy soil. Your soil should have an active soil food web and plenty of worms. The worms will actually come to the surface and harvest the organic matter as the leaves break down. This very effectively ‘cleans’ the fungal spores and removes them from beneath your tree.
Not sure if whether your soil has an active soil food web? If you don’t quite understand the key role it plays in the health of your garden, check out this short course.
If you find the leaves are not breaking down fast enough you can help them along by mowing them with the mower or slasher. A sprinkle of compost on top, or a spray them with compost tea or worm juice can also help them along.
Getting chooks or other animals on the job can really help too, as they’ll scratch and peck the leaves and help them to break down faster.