7 Reasons Your Tomato Plants Are Stressed and How to Fix It
If you’re having issues with your tomato plants this year, we can help! Join gardening expert Melissa Strauss to discuss some potential stressors and how you can fix them in time for a bountiful harvest.
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Tomatoes are one of the most popular crops among home gardeners. In fact, up to 86% of gardeners in the United States grow them every year. You can prepare these sweet, juicy fruits in so many ways, it’s difficult to even start a list!
On the whole, tomatoes are not difficult to grow. So it makes sense that so many gardeners not only grow them, but many get started this way in the first place. Tomatoes are a gateway to a full-fledged veggie garden.
If you’re growing them this year, you should be ready to handle any issues that crop up. There are a number of reasons that your tomato plants may experience stress, which could show up as languishing plants and subpar tomatoes. Let’s take a look at some common stressors and how to correct them to grow a bountiful harvest of tasty tomatoes.
Heat
Tomatoes are heat-loving plants, but there is such a thing as too much of a good thing. Particularly in warmer climates, too much sun or heat can stress out your entire veggie garden, including your tomato plants.
The ideal temperature range for these plants is around 85°F (29°C) during the day and 70°F (21°C) at night. When the days creep toward 95°F (35°C) and nights stop dipping below 80°F (27°C), your plants will stop producing red pigments. If you’re growing a red variety, this will make your tomatoes turn out orange. In this type of heat, they may cease to ripen at all.
In hot weather, you may see flowers drop and stunted growth along with fruits that refuse to ripen. Heat can disrupt pollination and turn your leaves yellow or brown. Eventually, the leaves may dry out and die.
How to Fix It
If you live in a hot climate, choose your varieties to match. Certain types are more heat-tolerant than others. Consider ‘Solar Fire,’ ‘Heatmaster,’ or ‘Celebrity.’ Offering your plants some afternoon shade is helpful in this type of climate as well.
Keep your tomatoes hydrated, as hydrated plants are more tolerant of stress of all types. Keep the lower branches thinned out to promote air circulation which will keep things cooler toward the interior of the plant.
Use mulch to help the soil retain moisture and offer some protection and insulation to the roots. If a heat wave is coming, go ahead and harvest your unripe fruits. Tomatoes continue to ripen after you pick them.
Water Issues
Both over– and underwatering can be issues that cause stressed tomato plants. Let’s talk first about underwatering, as this is the easiest to fix.
Underwatering
Underwatered tomatoes will be droopy, stressed, and wilted, and may have curling leaves. Overall, a lack of water leads to stunted growth, blossom drop, and dying foliage. Usually, you can catch this issue before anything extreme happens.
How to Fix It
Water thoroughly and regularly. Always water at the base of the plant, where the water will go directly to the roots rather than evaporating. Watering in the morning will also help get the water to the roots before the heat causes evaporation from the soil. A layer of mulch will also help hold moisture in the soil.
Overwatering
Too much water can cause similar symptoms to underwatering. You may see yellow, drooping leaves, which indicate root rot or other fungal issues. Fungus, in general, is the most detrimental issue caused by too much moisture.
How to Fix It
Allow the soil to dry slightly between waterings, but don’t allow it to become completely dry. Always water at the ground level rather than overhead. Water on the foliage can result in fungal diseases like powdery mildew.
If drainage is an issue, work on correcting it so that the soil drains properly. Thinning out the foliage will allow more sunlight to the interior of the plant, which will also help cut back on fungal issues. Always water in the morning. Wet soil at night is a breeding ground for fungus.
Lack of Nutrients
Tomatoes are heavy feeders, requiring significant nutrients to perform their best. Iron and magnesium deficiencies cause chlorosis, which is yellowing between the veins. Calcium and potassium deficiency can cause leaves to roll and blossom end rot in many cases.
Another nutrient issue is nitrogen deficiency, which causes the leaves to turn pale, yellow, or reddish. A lack of phosphorus may manifest as darkened leaves and stunted growth.
These deficiencies can result from a general lack of or depletion of nutrients in the soil. They can also be the result of soil that is too alkaline or the result of soil that isn’t watered properly. Tomatoes need slightly acidic soil to convert their nutrients into a form they can utilize.
How to Fix It
Fertilizing regularly is the number one way to prevent nutrient deficiency and stress in your tomato plants. It’s also a good idea to conduct a soil test up front to see if your soil is lacking in any of the macro or micronutrients your plants need. The test will also indicate the pH of your soil, which is helpful information.
Make sure that you water consistently. This enables your plants to take in the nutrients present in the soil. If a balanced fertilizer isn’t cutting it, consider buying a formula that meets the specific needs of a tomato plant.
Overabundance of Nutrients
Just as a lack of nutrients can be an issue, an overabundance can also be problematic. Too much nitrogen leads to excessive green growth and poor production. Your plants will be pretty, but they’ll produce fewer and lower-quality fruits. If it becomes extreme, you may see foliage burn.
Excess nitrogen and phosphorus interfere with calcium intake, resulting in blossom end rot and blossom drop. Blossom end rot manifests as a mushy brown spot at the blossom end of the fruit, and it destroys the tomato!
How to Fix It
Use a balanced, organic fertilizer for a slower, more gentle application of nutrients. When using fast-acting fertilizers, go easy, as over-fertilizing is more damaging than not giving them enough.
Perform a soil test ahead of time to ensure a good balance, and add limestone or gypsum to meet tomatoes’ considerable calcium needs.
If fertilizer burn occurs, there is nothing you can do to salvage that foliage, but you can flush the soil to prevent further damage. Scale back your fertilizing schedule and go with a gentler formula.
Over-Pruning
Pruning the lower leaves is a good practice that helps improve air circulation in your tomato plants, however, removing too many leaves can cause stressed, stunted crops.
Too much pruning can affect the plant’s ability to photosynthesize, making it weaker overall and less productive in most cases. Exposing the fruit to too much light can also lead to scalded fruit.
Removing too much foliage forces the plant to overcompensate for the decrease in photosynthesis. If other stressors, like nutrient or watering problems, are present, you can end up killing the plant altogether.
How to Fix It
It’s best to know what you’re doing from the start when it comes to pruning. Before you transplant, remove the lowest leaves. There should never be leaves that touch the ground.
As your plant grows, remove suckers, which grow upward from the axils, the place where a leaf joins with the central stem. Maintain clearance at the bottom six inches to a foot.
Keep an eye on your plants for pests and diseases, plucking off any affected foliage and disposing of it. Just be careful about the upper leaves. Never expose fruit to the sun; always leave coverage above your tomatoes to protect them from sunscald.
Pests
Tomatoes are tasty, and plenty of pests agree. Tomato hornworms, fruit worms, potato aphids, stink bugs, whiteflies, and a host of other insects will gladly dine on your crop if you aren’t keeping watch.
It’s typically easy to identify pest damage. Chewed leaves and fruit are a sure sign. You may also observe distorted growth of fruit and foliage, and generally unhealthy-looking plants, as many pests draw nutrients.
How to Fix It
I’m a proponent of using natural controls as much as possible. Insecticides are harmful to good insects like pollinators and beneficial predators. Once you eliminate these, the pest populations will increase exponentially.
Neem oil, used in the evening, is a safe and effective solution for many pests. Picking off the larger pests is also a good control. Natural pesticides made with helpful bacteria (like Bt) are good for controlling caterpillars.
Diseases
Tomato plants are also susceptible to quite a few diseases. Many of these are fungal, which is commonly the result of poor watering habits. You may notice powdery mildew on lower leaves, or yellowing or browning of the foliage. Some fungal diseases can cause leaf spots or lesions.
Viral and bacterial diseases also affect these plants, so it’s essential to watch for their symptoms. Sunken spots in the fruits or wilted foliage can indicate a bacterial issue. Mosaic viruses will manifest in mottled leaves.
How to Fix It
Some fungal diseases are easy enough to treat. Improving air flow and increasing sun exposure to the center of the plant will help in many cases. Neem oil is also great for treating certain fungal diseases.
Some fungal diseases, like late blight, spread quickly, so few solutions exist. Removing affected plant parts is helpful, and you can treat with copper-based fungicides or neem oil.
Sadly, some diseases have no treatment. Fusarium wilt and most viral diseases are incurable. The best way to treat them is to remove all affected foliage and hope for the best. Disposing of the entire plant is often the best way to prevent it from returning next year.
Some viral diseases come in with various pests. Proper pest management is the best prevention for these. Maintain a healthy balance of beneficial insects in your garden to keep pest populations down in the natural way.
