Tomato hornworm is shown in photo above.
There's more to growing tomatoes than simply planting them (deeply) into soil and then keeping up with watering.
Turns out, there's a LOT more to know about cultivating a great crop of tomatoes! Here's what to look for in your tomatoes, and solutions for keeping your plants healthy and producing beautiful tomatoes.
Curled leaves means your plant is stressed
If leaves curl upward or inward but stay a healthy green, the cause is likely heat, drought, wind, or over/underwatering. Leaf curl is the plant's way of conserving moisture.
What to do about leaf curl
Yellow Leaf Curl
Different from regular leaf curl (as noted above). This is a virus, transmitted by whiteflies. The leaves curl, turn yellow, you'll see a sticky residue, and clouds of tiny white flies when plants are disturbed. Whiteflies can't survive our cold winters, so they are mostly an issue for greenhouse and indoor plants. However, if you have outdoor plants with whiteflies, it is likely that it was introduced into your garden through infested plants you purchased at a nursery or greenhouse grower.
What to do
Prevent bottom end rot and improve soil quality due to nutrients leaching out over time
With consistent watering, the nutrients will understandably leach out of the soil, leaving it without enough of what tomatoes need to set and produce fruit.
What to do
Fungal disease early blight
Early blight is a common fungal disease characterized by dark, circular lesions with a bullseye pattern on leaves, stems, and fruit. It typically starts on the lower leaves and progresses upwards. Can lead to reduced yields.
What to do
Tomato hornworm and cutworm
Tomato hornworms and cutworms are both garden pests that can damage tomato plants, but they differ in their appearance, feeding habits, and preferred locations on the plant. Tomato hornworms are large, green caterpillars with white and black markings, and a horn on their rear end, feeding on tomato leaves and sometimes fruit. They'll do big damage to your tomato plants quickly. Cutworms, on the other hand, are dull-brown caterpillars that hide near the soil line and can cut off seedlings at the base.
What to do
To remove hornworms, wear thick gloves to pick them off the plant and relocate them (more than 10 feet away) or dispose of them. They don't bite or sting, but using gloves is recommended. Another method is to use a scissors to cut them in half right on the plant as you see them.
For cutworms, which curl up upon being touched, diatomaceous earth (DE) is recommended. This powder is made of ground-up fossils and is harmless to humans and larger animals (as long as not consumed), but excellent for tiny creatures like cutworms. Lots more info on cutworms is here.
Herbicide Damage
Herbicide drift (like from lawn weed killers) or contaminated compost causes the leaves of tomatoes to become twisted or distorted.
What to do
There's no fix - plants may outgrow mild damage if new growth looks normal
Avoid spraying pesticides near any vegetables and never spray on a windy, even breezy day.
Be cautious using grass clippings from treated lawns.
Fertilize - tomatoes are known to be 'heavy feeders'
Fertilizing tomatoes is essential because it provides the nutrients they need to grow strong roots, produce healthy foliage, and set abundant, flavorful fruit.
Fertilize tomatoes by starting with a balanced fertilizer at planting (NPK ratio like 10-10-10 or 20-20-20), then switch to a low-nitrogen, higher phosphorus and potassium fertilizer once flowers appear (NPK ratio like 5-10-10, or 8-32-16). Feed every 2–4 weeks during fruiting, watering deeply afterward. Always follow label directions and avoid over-fertilizing — too much nitrogen makes lots of leaves but fewer fruits.
Curled leaves means your plant is stressed
If leaves curl upward or inward but stay a healthy green, the cause is likely heat, drought, wind, or over/underwatering. Leaf curl is the plant's way of conserving moisture.
What to do about leaf curl
- Water deeply and consistently, but don't overdo it. Just keep the soil evenly moist.
- Mulch around base of plant to keep the roots cool and moist.
- Provide afternoon shade (shade cloth or Agribon works well) if we're experiencing a hot spell (temps over 85 degrees F)
- Don't over fertilize (too much stresses the plant). Over-fertilizing can lead to excessive foliage growth at the expense of fruit production.
- Spray plant leaves with a solution of two tablespoons Epsom Salts to one gallon cold water. A regular spray bottle can be used for this solution. Simply thoroughly mist the leaves (top and bottom) on a cool morning as a helpful remedy for magnesium deficiency in tomato plants, which can cause leaf curl. Don't over apply (once every three weeks or once a month should be all that's needed).
Yellow Leaf Curl
Different from regular leaf curl (as noted above). This is a virus, transmitted by whiteflies. The leaves curl, turn yellow, you'll see a sticky residue, and clouds of tiny white flies when plants are disturbed. Whiteflies can't survive our cold winters, so they are mostly an issue for greenhouse and indoor plants. However, if you have outdoor plants with whiteflies, it is likely that it was introduced into your garden through infested plants you purchased at a nursery or greenhouse grower.
What to do
- Remove infected plants immediately - there is no cure.
- Grow resistant tomato varieties (i.e. Better Boy, Bush Celebrity Hybrid) if you've experienced this in the past or don't want to risk it in the future. CSU Extension says when purchasing tomato varieties, always select plants labeled “VFN,” “VFNA,” “VFNT,” etc. This indicates that the plants are resistant to Verticillium wilt (V), Fusarium wilt (F), southern root-knot nematode (N), early blight (A), or tobacco (tomato) mosaic virus (T). Selecting resistant plants may eliminate many disease problems.
Prevent bottom end rot and improve soil quality due to nutrients leaching out over time
With consistent watering, the nutrients will understandably leach out of the soil, leaving it without enough of what tomatoes need to set and produce fruit.
What to do
- Try Calcium Nitrate (at local stores and Amazon for $10). One tablespoon sprinkled around the outside of the stem (not touching the stem) works wonders to replenish the nutrients that have likely leached out of the soil. Calcium Nitrate contains calcium and nitrogen, both of which are essential for robust tomato growth. It strengthens cell walls, improves fruit quality and yield, and potentially reduces the impact of certain diseases and pests. Sprinkle once or twice per season (application spaced two to three weeks apart is recommended) around the time in the growing cycle when fruits are starting to form. Calcium nitrate also helps to prevent blossom end rot (which is caused by a calcium deficiency).
Fungal disease early blight
Early blight is a common fungal disease characterized by dark, circular lesions with a bullseye pattern on leaves, stems, and fruit. It typically starts on the lower leaves and progresses upwards. Can lead to reduced yields.
What to do
- Remove and destroy infected leaves, stems, and fruit throughout the growing season.
- At season's end remove all plant debris to reduce overwintering of the fungus.
- Apply fungicides early in the season (copper-based fungicides i.e. 'fixed copper' are an organic option), when symptoms first appear, to slow disease.
- Provide adequate spacing between plants for best air circulation
- Water at base of plant and avoid splashing water on foliage
- Rotate crops to avoid planting tomatoes in same location year after year
Tomato hornworm and cutworm
Tomato hornworms and cutworms are both garden pests that can damage tomato plants, but they differ in their appearance, feeding habits, and preferred locations on the plant. Tomato hornworms are large, green caterpillars with white and black markings, and a horn on their rear end, feeding on tomato leaves and sometimes fruit. They'll do big damage to your tomato plants quickly. Cutworms, on the other hand, are dull-brown caterpillars that hide near the soil line and can cut off seedlings at the base.
What to do
To remove hornworms, wear thick gloves to pick them off the plant and relocate them (more than 10 feet away) or dispose of them. They don't bite or sting, but using gloves is recommended. Another method is to use a scissors to cut them in half right on the plant as you see them.
For cutworms, which curl up upon being touched, diatomaceous earth (DE) is recommended. This powder is made of ground-up fossils and is harmless to humans and larger animals (as long as not consumed), but excellent for tiny creatures like cutworms. Lots more info on cutworms is here.
Herbicide Damage
Herbicide drift (like from lawn weed killers) or contaminated compost causes the leaves of tomatoes to become twisted or distorted.
What to do
There's no fix - plants may outgrow mild damage if new growth looks normal
Avoid spraying pesticides near any vegetables and never spray on a windy, even breezy day.
Be cautious using grass clippings from treated lawns.
Fertilize - tomatoes are known to be 'heavy feeders'
Fertilizing tomatoes is essential because it provides the nutrients they need to grow strong roots, produce healthy foliage, and set abundant, flavorful fruit.
Fertilize tomatoes by starting with a balanced fertilizer at planting (NPK ratio like 10-10-10 or 20-20-20), then switch to a low-nitrogen, higher phosphorus and potassium fertilizer once flowers appear (NPK ratio like 5-10-10, or 8-32-16). Feed every 2–4 weeks during fruiting, watering deeply afterward. Always follow label directions and avoid over-fertilizing — too much nitrogen makes lots of leaves but fewer fruits.
When to Worry
- If the plant looks mostly healthy, mild curl or a few spots isn’t a big deal.
- If there’s yellowing, stunted growth, or sign of insect or fungal damage, investigate further (see above for information and solutions).