Skip to Content

5 Mistakes That Cause Tomato Leaves to Curl (And How to Fix Them)

Growing fresh tomatoes is a highlight for many garden enthusiasts. What’s more rewarding than enjoying tasty veggies you’ve nurtured yourself? However, growing tomatoes can sometimes be tricky.

Tomato leaves curling is often a sign of stress due to less-than-ideal growing conditions, insufficient water, or a lack of nutrients. To remedy this, shield your tomatoes from intense sun and heat, ensure the soil is moist by watering it when the top inch dries out, and feed your plant with fertilizer at least twice during the growing season.

1. Growing Conditions

Tomato leaves curling because of temperature stress.

Tomato leaves curl because of temperature stress.

Tomato leaves curling is often a response to challenging growing conditions. One common cause is extreme heat. When temperatures soar above 90°F (32°C), the plant may experience stress, leading to curled leaves. This is because the roots struggle to supply enough water to the leaves, despite the soil being moist. Curling helps the tomato minimize moisture loss by reducing the leaf’s surface area exposed to the air, thus preventing the leaves from drying out.

Another issue arises with too much sunlight. While tomatoes thrive in direct sunlight, the midsummer sun can be overly intense, causing stress or even sunburn to the plant. Often, heat and sunlight combine to significantly impact the tomato’s health and appearance.

However, leaf curling due to heat and sun exposure usually isn’t deadly. The leaves might not uncurl, but the plant should continue to grow and produce fruit.

Solution:

  1. Provide some shade for your tomatoes during particularly hot days to protect them.
  2. Increase watering slightly during very hot summers to ensure they have enough moisture.
  3. Ensure good air circulation in your garden to help moderate temperatures and reduce stress on the plants.

2. Watering Issues

Tomato leaves curling because of underwatering.

Tomato leaves curling because of underwatering.

Tomatoes require ample water to fruit properly. However, during a summer drought, the soil might not retain enough moisture, leading to leaf curling as a protective measure against water loss in hot conditions, similar to the reasons mentioned earlier.

Solution:

  1. Keep a constant check on soil moisture levels.
  2. Water your tomatoes once the top inch of soil feels dry.
  3. When watering, ensure it’s thorough so that the water reaches the full depth of the roots.
  4. Be careful not to overwater, as this can also affect the plant negatively.

3. Lack of Nutrients

Tomato leaves curling because of improper fertilization.

Tomato leaves curling because of improper fertilization.

Fertilizer is key to producing large, juicy tomatoes, as typical garden soil often lacks the nutrients tomatoes need to thrive. However, fertilizing incorrectly can create issues.

One common problem is too much nitrogen in the soil, which can occur with fertilizers high in nitrogen compared to other nutrients. This imbalance often leads to overly vigorous leaf growth and downward curling of the leaves.

Another issue is the overall scarcity of nutrients in the soil, leading not only to leaf curl but also to yellowing leaves. Additionally, the plant’s growth can slow, and its fruiting may be sparse.

Solution:

  1. Enrich the soil with high-quality fresh compost; a bucket per plant is usually sufficient to boost your tomatoes’ health.
  2. Opt for a multi-purpose, slow-release fertilizer that provides a balanced ratio of nitrogen, phosphorus, and potassium (NPK).
  3. Apply fertilizer in the spring, before the tomato plants start fruiting, to support their growth and development effectively.

4. Tomato Yellow Leaf Curl Virus

Tomato leaves curled by TYLCV

Tomato leaves curled by TYLCV

Viruses present a significant challenge for gardeners, as they are tough to manage. In certain farming areas, the damage caused by viruses can be extensive.

The Tomato yellow leaf curl virus is notably prevalent among tomatoes. This virus manifests through the upward curling of leaves, a deformation that’s typically severe and distinct from other curling causes. Additionally, parts of the leaf may turn yellow, resembling chlorosis.

Solution:

  1. Regularly spray your plants, tomatoes included, with horticultural oil. This significantly lowers insect populations, cutting down on the likelihood of virus transmission.
  2. Should you notice a tomato plant with yellowing and curling leaves (similar to what’s described), it’s best to remove it promptly to prevent further spread of the virus.

5. Pest Infestation

Aphids

Tomato leaves curling because of aphids.

Tomato plants face many insect foes, but aphids are often the chief culprits behind leaf curling. These tiny, sap-sucking pests come in shades of gray or green and tend to congregate on the undersides of leaves.

The damage from their feeding results in leaves curling upwards, and you might also notice bumps or tubercles on the leaves where aphid populations are thickest.

Solution:

  1. Treat your tomatoes with horticultural oil, which is generally effective in getting rid of aphids.
  2. If the problem persists, don’t hesitate to apply the oil treatment again.
  3. Avoid using chemical pesticides on aphids to ensure your tomatoes remain safe to eat.