Why are my tomato seedlings turning yellow?

A variety of causes may produce tomato leaf discolouration, including nutritional shortages, plant diseases, and cultural issues. We’ll assist you in determining the reason of yellowing leaves on your tomato plants and providing remedies.

Tomatoes are one of the most popular crops for home gardeners, especially novices, but they are also one of the most difficult. They may be hosts to a variety of pests and illnesses, and their nutritional needs are substantial, which is why they are referred to as “heavy feeders.” Yellowing leaves on tomato plants might indicate a variety of issues, ranging from nitrogen shortage to overwatering to herbicide damage, but don’t worry – yellow leaves are quite frequent and have several possible treatments.

Some Yellow is Common with New Plants

If your newly purchased tomatoes have some yellow foliage, don’t worry, especially if they were tall and gangly plants growing in a small pot before you planted them in their new home in your vegetable garden. Yellow growth is a typical issue for certain nursery-grown vegetable plants, caused by either competition from nearby plants or diminishing nutrient levels in the potting mix.

To optimize the area available for developing plants, nurseries should pack tomato seedlings closely together. Lower leaves of tomato seedlings are shadowed by surrounding plants as they grow toward the sky. Lower leaves may turn yellow and even fall off if less sunshine reaches them. Once that plant is properly spaced and growing in its new home in the vegetable garden, yellow leaves will probably be less of an issue.

Although the garden center probably made sure there was plenty of fertilizer mixed in with the tomato seedling’s potting mix, that hungry young plant may have depleted some of those nutrients resulting in yellowing leaves. The good news is that garden soil is generally rich in minerals that tomato plants need to flourish, particularly if there is a lot of organic matter in the form of compost, manure, or decomposing mulch. Let your tomatoes a week or two to establish roots in the natural soil of your garden. Of course, it’s always a good idea to do a quick soil test to find out what nutrients are available to your veggies and how much fertilizer should be added to maximize growth.

Be Sure to Buy Healthy Plants

Yet, yellow leaves might be a sign of other health problems, such as communicable plant infections. When buying tomato plants from a garden center, look for healthy plants with stocky growth and green leaves that are free of spots or fading. Unhealthy bargain plants can introduce pest and disease problems that can take years to eliminate from the garden.

Nutrient Deficiency is a Likely Cause

The most prevalent cause of yellowing leaves on established tomato plants is a lack of nutrients in the soil. Tomatoes are extremely heavy feeders and require plenty of nutrients to grow healthy and be fruitful.

In the tomato plant, signs of nutrient shortage often begin low.

Although a lack of nitrogen is usually the reason why tomato leaves are yellow, it’s important to correctly identify which nutrient is deficient before reaching for a high-nitrogen fertilizer. A surplus of certain nutrients may lead to a deficit of others. To determine exactly what nutrients your tomatoes need, identify where the yellow leaves are on the plant and which parts of the leaves are yellowing, and run a quick soil test to determine exactly what nutrient your tomatoes need.

Are the Plant’s Older Leaves Turning Yellow?

Certain nutritional deficits will manifest themselves in the older leaves lower down on the plant. This means that the tomato was able to move nutrients from older growth to new leaves that need those minerals the most. Nitrogen, potassium, and magnesium deficits may produce yellowing of older leaves.

• In the case of nitrogen If there is a deficit, the whole leaf will become yellow. While tomatoes (like other plants) need nitrogen to develop, it is critical not to use too much nitrogen fertilizer. Too much nitrogen promotes luxuriant vegetative development at the expense of flower and fruit yield.
• A lack of potassium will cause the leaf’s outer edge to yellow before becoming brown and seeming scorched. A good dose of potassium, either in the form of added fertilizer or what’s already available in the native soil, is key to tomato fruit quality and yield.
• Tomatoes that don’t have enough magnesium will sprout golden leaves with green veins. If you’re certain you’re deficient in magnesium, try a DIY Epsom salt combination. Combine two tablespoons of Epsom salt with a gallon of water and spray the mixture on the plant. If the problem was truly due to magnesium deficiency, leaves should start to become green within a week of treatment.

The yellowing of the tomato leaves’ outer edges might suggest a potassium deficit.

Are the Newer Leaves Turning Yellow?

Plants do not transport all nutrients. Certain nutrient deficits will be seen in new growth at the tips of branches and towards the plant’s crown. Younger leaves might become yellow due to a lack of calcium and iron.

• In addition to yellow leaves, calcium Deficiency may also cause blossom end rot, which causes huge brown or black patches on the bottoms of tomato fruits.
• A lack of iron will cause tomato leaves to become yellow with green veins.

First Soil Test, Then Fertilize

Do a quick soil test before applying fertilizer. The findings of the tests will include the quantity of nutrients in the soil, the pH level of the soil, and advice on what items should be applied. Most fertilizers designed primarily for tomatoes or vegetable plants should include nutrients that cause yellow foliage.

The pH level is significant because it influences nutritional availability. If the soil is too acidic, plants will have a hard time absorbing calcium and magnesium. On the other hand, alkaline soil limits the amount of iron that plants can absorb. Tomatoes thrive on soil with a pH of 6.5 or higher.

Tomatoes are subject to a variety of illnesses and pests, many of which may cause yellowing of the leaves. If you suspect that your tomato plant has a bacterial or fungal disease or is being eaten by insects or mites, reach out to your local agricultural extension service for help diagnosing the problem and finding a solution. Your state extension program’s website may offer information about tomato health issues that are widespread in your region. The Home & Garden Information Center at Clemson University, for example, has a whole website devoted to tomato illnesses and problems.

Plants receive nutrients and water via their roots. Water transports these essential nutrients into and through the plant to where they are most required. This means that even in fertile soil, your tomatoes may show signs of nutrient deficiency if they aren’t getting enough water. Tomatoes need about an inch of water a week early in the growing season and two inches a week when they begin fruiting.

Rather than watering a little bit every day, water deeply twice a week (depending on the weather), allowing water to penetrate about a foot into the soil. Water the soil around the base of the plant thoroughly if you’re using a watering wand hose attachment or a watering can. Pause as water starts to runoff or roll away to enable all of the water to soak into the soil. Give the plant another drink when there is no more standing water. Instead, a soaker hose may be used to supply water at a gentle drip.

Deep, infrequent watering is an excellent method for training tomato roots to grow deep into the soil. This practice will make plants more resilient to stress, and the widespread root system will have an easier time finding nutrients in the soil. Watering tomatoes requires consistency, particularly as fruit starts to form. Fruits that crack open or develop blossom end rot are signs of over- and under-watering.

When it comes to fertilizing your plants, always follow the instructions on the product label. This ensures that your plants receive the nutrients they need while minimizing fertilizer runoff and crop damage. If the label calls for “sidedressing,” that means the fertilizer should be applied next to rather than directly on the plants — usually 4 to 6 inches away from the plants themselves.

Too much of a good thing may be harmful, and this is especially true in the case of fertilizers. Adding more fertilizer than the label specifies (either too much at one time or applying too frequently) can burn tomato roots. If you’re growing tomatoes in containers, fertilizers and other salts in the water can build up in the pot, leading to salt injury or fertilizer burn. To wash away surplus salts, thoroughly wet the pot until water drips from the pores in the bottom.

Weed control is a constant task for all vegetable growers. While it may be tempting to use a herbicide (whether synthetic, organic, or homemade), bear in mind that tomatoes are very susceptible to chemical weed management. Even if herbicides are not directly sprayed to tomato plants, herbicide drift may cause plant harm, resulting in stunted yellow development. Instead of using pesticides, control weeds in the vegetable garden by hand weeding, mulching, and spacing plants closely enough to restrict weed competition.

With the correct circumstances, tomato leaves are sensitive to sunburn. Early in the season, sunscald is frequent on freshly planted tomatoes, particularly if the seedlings are accustomed to growing inside under a grow lamp. “Hardening off” is a key step in preparing vegetable seedlings for planting in the garden.

Begin the hardening off procedure two weeks before you want to plant your tomatoes in the garden. Just place potted seedlings in a shaded location outside and bring them inside at night. If temperatures fall below 45 degrees Fahrenheit, stop hardening off until the weather improves.

If you intend to buy tomato seedlings from a garden center, keep your plants protected from sunscald on the way home. Avoid keeping plants in the vehicle for extended periods of time, and make the plant nursery your last visit before heading home. If at all possible, avoid having tomato leaves rub up on the vehicle glass.

Sunburn may occur on older, established plants as well, particularly when the summer days heat up. Tomatoes that are growing on exposed west- and south-facing sites, or are sited near a reflective surface like a block wall, may grow better with some protection from a shade cloth.

Go Easy on the Organic Matter

Although it is uncommon, another cultural issue that causes leaves to yellow is the use of too much organic materials as soil additions, such as leaves or sawdust. The amount of carbon material in these circumstances might deplete the soil of nitrogen, which could be supporting your tomato plants. It’s particularly difficult if the amendments aren’t adequately integrated into the soil, so keep ratios and correct mixing in mind when adding organic matter to your soil.

Related Questions

• What causes yellow leaves on tomato seedling?

  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 suggest watering only when necessary, since tomatoes despise wet feet.

• Can yellow seedlings recover?

  As a leaf loses its chlorophyll, the plant abandons it and starts to absorb the leaf’s remaining nutrients. That is why, once a leaf becomes yellow, it is often impossible to convert it back green. (But, in circumstances of nutritional deficits, yellow leaf color may occasionally be restored with therapy.)

• How often should I water tomato seedlings?

  Water freshly planted tomatoes well to ensure that the soil is wet and suitable for growth. Watering plants everyday in the morning early in the growth season. When the weather rises, you may need to water tomato plants twice daily. Garden tomatoes typically require 1-2 inches of water a week.

• Why are my seedlings turning yellow?

  A nutritional shortage is most likely to blame for the yellow-green tint. When flower and vegetable seedlings are started inside, nitrogen and phosphate shortages might emerge. Yellow-green leaves and reduced plant development are signs of nitrogen shortage.