Tomato Plant Problems - Yellow Leaves

Posted on 05 March 2020

Common Seed Customer Question:
“Why are some of my tomato seedlings are looking yellow?”

If your tomato plants leaves are turning yellow, this could be from a wide variety of reasons, however, before we go on, we have one thing to note:

If the first leaves on your tomato seedings (called “cotyledons”) are turning yellow and falling off, don't worry! This is a normal part of seedling development, o
nce the raggedy “true” tomato leaves appear, the first two cotyledon leaves may drop off on tomato plants as well as other vegetable plants. 

Below are two examples of yellowing cotyledon leaves on tomato seedlings: 

Tomato Plant Problems - Yellow Leaves

Tomato Plant Problems - Yellow Leaves falling off

More reasons for Yellowing Leaves on Tomato Plants:
There are many reasons why a tomato plant's leaves turn yellow. Under-watering and over-watering can both cause yellowing leaves, as well as nitrogen deficiencies in the soil, a lack of sunlight on the bottom leaves, or a possible disease (which tomatoes have plenty of). We recommend making sure to water only when needed, as tomatoes hate soggy feet. Water when the soil is starting to dry out, garden tomatoes typically require about 1-2 inches of water a week, depending on the weather and climate. 

Compost & Mulch:
Make homemade compost and top dress your garden soil to help keep your soil rich and full of nutrients. This may eliminate the need for fertilizer entirely, which is best, especially in organic gardens. Mulch your tomato plants to help conserve moisture. 

Fertilizing Tomato Plants:
Homemade compost is best and is free! But you can also use slow-release organic fertilizer if needed. We've also heard good things about using Cottonseed meal as a natural tomato fertilizer that can be mixed into your soil when planting. It contains nitrogen, phosphorus and potassium (6-2-1 ratio), plus including calcium, magnesium, sulfur, copper, and also provides trace elements such as manganese, molybdenum and zinc. Plus it's nitrogen supports leafy growth on young tomato plants. Cottonseed meal nutrients are released slowly and last about four months. Fish Emulsion is also another natural fertilizer that helps tomato plants throughout the season. 
Tomato Seeds

Grow a Variety of Tomato Varieties:

To increase your odds of a successful tomato harvest, we recommend growing both Heirloom and Hybrid tomatoes.Grow Heirloom open-pollinated tomato seeds for great flavor and seed saving, and grow Hybrid tomatoes for vigor, yield and better disease resistance.

Check out all of our 44+ Tomato Seeds »

We find that different tomato varieties (both heirloom and hybrids) perform differently from season to season, depending on the weather and soil & pest conditions. Where one season a hybrid or heirloom may thrive, the next season it could be the one plant that gets riddled by aphids or develops a disease. By growing a several varieties of different types of tomatoes each season, your chances for success are much greater! If you do find a diseased or pest-infested tomato plant in your garden, we recommend removing it – once they get sick they usually continue to struggle all season, and we don't recommend spraying them with chemicals. Simply take that tomato out, if you've planted several others you should still have a great harvest. 

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