Gardening Plant diseases

Should I Remove Diseased Plants From My Garden?

It’s fall! Time to drag your kids apple picking. The forests are on fire (the trees have flamboyant leaf colors, that is). And we finally get a break from the summer heat. Doesn’t it feel nice to be wrapped in a fleece hoodie!

Powdery mildew on a squash leaf.
Powdery mildew on a squash leaf. Photo: Ejdzej, Wikimedia Ccommons

But our gardens are beginning to suffer. The colder it is, the more plants decline. Your vegetable garden is less and less productive. And the diseases! OMG! Your tomatoes have downy mildew. Your phlox has powdery mildew! How many kinds of mildew are there anyway? Things aren’t going that well in your garden!

Seek And Destroy!

You may have been told that when a plant is sick, it is absolutely necessary to remove and destroy the infected parts. That seems to make sense! That way the disease can’t spread to other plants. Otherwise, the diseased leaves will fall to the ground and infect the soil. The following year, the diseases will come back in full force! It’s going to be a gardening apocalypse!

Powdery midew spores
Fungus spores are microscopic. They can be present without being seen. Photo: Cesar Calderon, Wikimedia Commons

Except… That’s Not Necessarily True!

Yes, the powdery mildew on your squash leaves could infect others. But, probably the worst is already done. Mildew is a fungus. Fungi are propagated by spores, which are like miniature propagules (but not true seeds) that float in the air. So if it’s on your leaves, it’s probably everywhere! On other plants, on the ground, in your face!!! Is it really worth removing diseased leaves? Well, don’t forget that as long as the leaves are green, they are still carrying out photosynthesis. Isn’t it better to leave them there to do their job?

And even if you removed all the diseased plants, there would be fungus and bacteria on other plants. What if you took out all the plants and all the soil and everything else throughout your whole garden? Well, you discover the little pests are hiding at your neighbor’s, waiting to surprise you come spring. It’s like trying to get rid of dandelions! It’s a lost cause.

Tomatoes on a plant infected by mildew
Leave sick leaves and branches in your garden. They will decompose and feed your soil. Photo: pitrs10,

Leave The Sick Behind

OK, this is controversial, but… I recommend leaving your sick plants in your garden for the winter. Seriously! Since everything is infected anyway, you might as well let them decompose and feed your garden…as Mother Nature always intended. After all, the best food for a plant is its own decomposed stems and leaves.

You could also put them into your compost. There is a good chance that the fungi and bacteria will suffer a gruesome death at the hands of your compost pile. No, composting does not necessarily kill all diseases, especially the cold composting most of us do at home. But it still destroys most sources of infection. And at least your sick plants will be well nourished when you use the compost to help them grow in coming years.

Vegetable garden with raised beds
Crop rotation helps reduce the spread of diseases in the vegetable garden.. Photo: Sten Porse, Wikimedia Commons.


“Wait a minute! Are you telling me that all my plants are always going to be sick for the rest of time and there’s nothing I can do about it?”

That’s pretty much it! At some point, gardeners just have to accept that disease is normal in plants, just as in humans. But you don’t need to go to the hospital for a cold. Nor do plants necessarily need hospital-level sterility for minor problems like powdery mildew. But there are still a few simple things that can solve the problem that don’t involve setting your flowerbeds on fire.

Start by using crop rotation in your vegetable garden. Disease spores overwinter in the ground, but if you plant your tomatoes somewhere else the following year, the chances of spores being in that spot are minimal! And the squash you put in their place won’t be affected by its own version of powdery mildew. Most diseases are host specific.

Disease Resistance to the Rescue

You could also use disease-resistant plants! Or at least more resistant varieties. The progress made in this field is amazing! Yes, there are squashes and phlox that resist powdery mildew and tomatoes that are resistant to all sorts of diseases. If you pick champions, you have a better chance of winning a championship!

Mathieu manages the and websites. He is also a garden designer for a landscaping company in Montreal, Canada. Although he loves contributing to the blog, he prefers fishing.

2 comments on “Should I Remove Diseased Plants From My Garden?

  1. Good advice. Like us if plant are exposed to a variety of microorganisms it can also help boost their immunity. Evolution at work.

  2. Cathleen Mahome

    Thanks, Mathieu, for continuing the Laidback Gardener tradition!

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