Tomatoes, Part II: “Why Are My Tomato Leaves Turning Yellow?”

Tomatoes, Part II: “Why Are My Tomato Leaves Turning Yellow?”

By Michael | Jenkins

As we read through your comments and questions, we’ve noticed that a great many of you have questions along the lines of “why are my tomato plant’s leaves turning yellow?” The truth is this is a really common problem, and that most gardeners and tomato growers have to deal with it from time to time. So, if this is happening to you, please know that you’re not alone! Tomato leaves turning yellow happens routinely, and there are a number of possible solutions. The challenge is, that there are a number of solutions because there are a myriad of potential causes for yellowing tomato leaves. Yellow leaves are the tomato equivalent of “cold-like symptoms” in a human being. So let’s run down the list of possible causes for your yellow tomato leaves and what you might do about them.

Before we move into that, let’s start with one quick note: the baby leaves (also called cotyledon leaves) your tomato puts out after it sprouts will yellow as the full grown leaves start to come in. This is normal, so don’t fret if that’s the issue. Healthy leaves should grow in fairly quickly.

So, why are your leaves turning yellow?

  • Early in the season, you may notice that your tomatoes’ leaves are turning yellow after you move them into the garden. This may be transplant shock, which many plants experience after being transplanted. Tomatoes, and in particular tomato seedlings, have delicate root systems and are fairly susceptible to transplant shock. So be gentle during transplanting, water your plants thoroughly after transplanting, and be patient. Your tomato plants just went through a major change, and they may need some time to recover.Here, I’d like to introduce a new type of plant pots which can 100% avoid transplant shock, that is Gardzen Marry Pots. When it’s time to transplant into a larger container, simply remove the bottom and place the Marry Pot on the top of a bigger container filled with soil. No way to ruin root system or bother plants.
  • Over- and under-watering are another common cause of yellow tomato leaves, and fortunately this issue is fairly easy to fix. Most tomato varietals require about 2 inches (5cm) of water a week—though they may need more or less depending on climate and weather conditions. Watering consistently and in harmony with the weather is a must for tomato plants—use a soil testerto make sure that your water and soil pH are within the parameters tomatoes enjoy! Slow, deep watering is best for tomatoes; heavy aggressive watering can disrupt the sensitive roots and cause other problems. And make sure you’re watering the roots, not the leaves; spraying down the foliage doesn’t actually help your tomatoes!
  • Compacted soil can lead to poor aeration and water absorption, both of which can lead to yellow leaves on your tomato plants. If the soil is overly dense or compacted, your tomatoes’ roots can’t move nutrition, oxygen, and water so the plant effectively suffocates. The best cure in this case is prevention: make sure your beds have nicely tilled or enrich soil full of organic material before planting or transplanting your tomatoes. Supporting soil health by introducing worms to your garden can also help, as can treating your soil properly. Avoid stepping on the soil around your plants; it can lead to soil compaction over time. You can also manually loosen your soil by stirring it up with your fingers, but be careful of your plants’ roots.
  • Tomato disease are another issue that may lead to yellow leaves on your tomato plants, but they’re less likely than the other options listed here. They’re also worth a blog or two in and of themselves, so they’ll be the topic of Part III, coming next week!

We hope this helps you diagnose and treat your tomato plants. Fresh tomatoes are such a wonderful gift from the garden, and we want to ensure you enjoy them as much as possible this season. If you have questions, tips, or tricks to share, please get in touch either here or find us on social media. We love to hear from you!

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