My tomatoes always seem to start out strong, I believe partly due to my mixture of manure, compost, and organic fertilizer. Every year I hold my breath, waiting for the first green fruits to catch my eye.
But no sooner do I start seeing those baby tomatoes do I also notice the bottom of my plants turning yellow. Many leaves also have brown spots.
Why do my tomato plants always seem to have yellow leaves at the bottom? And what can I do about it?
When the bottom leaves of a tomato plant turn yellow with brown spots, early blight is usually the culprit. Early blight is a fungus that occurs and spreads in wet and humid conditions. Since the fungus originates from the soil-level, early blight begins on leaves toward the bottom of the plant. When rain splashes on the ground, the fungal spores attach to the low-lying leaves.
What to do?
Not wanting to use fungicide mainly because I can be lazy/cheap and don’t want to buy it, I go a different direction.
I simply cut off the yellowing stems. Not only are the lower leaves shaded most of the time, I also know that by cutting these leaves off, I could inhibit the pathway for the fungus to reach the rest of the plant.
Though I still have a few issues with the yellowing leaves during the season, for the most part (thanks partly to a the hot and dry summers we usually have) the plants rebound and produce healthy red tomatoes.
Do you have early blight on your tomatoes? Here are five recommendations:
Clip stems as soon as you begin to notice the yellowing of the lower leaves with brown spots. If you let them stay on the plant, the fungus will travel up the plant. By catching it early, you won’t have to take away too many leaves and stems.
Clip the lower leaves, even if they’re unaffected. When the plant reaches about 18″ high, clip all stems growing on the lower 6″ of the plant. As the plant grows higher, aim for no stems on the bottom 12″ of the plant. If the leaves are allowed to touch the soil, early blight will continue to spread.
Mulch thickly. Since early blight originates in the soil, inhibit its path to the plant by laying on a 4″ layer of mulch around the tomato plant. My preference is wood chips, but I also have used other methods as well, as I talk about in this post.
Continue checking for yellowing over the next few weeks, especially after a rain.
Tie up any stems touching the ground, even if they are healthy. They run the risk of being affected eventually. A good tomato trellis should eliminate this step.
Important things to know about the yellow leaves on the bottom of your tomato plant:
The yellow leaves will not return to green. Once a leaf is affected, there really isn’t hope for that leaf and even that stem. Cut it off as quickly as possible to stop the spread up the plant. Most likely, your upper leaves — which receive the light anyway — are still healthy if you caught it early enough.
One More Suggestion
If you continually battle early blight, I share a quick tip in this video that I’ve found to help me in my garden:
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