I like to grow tomatoes as a summer plant in my container garden. But I’ve faced a problem where the leaves seem to fall off.

Your tomato leaves are falling off because there is a lack of nitrogen in the soil. Nitrogen is an essential macronutrient that encourages foliage growth on plants. You need to add an organic nitrogen-rich fertilizer such as bone meal, blood meal, alfalfa meal, or kelp to the soil.

Many other problems can cause the tomato leaves to fall such as lack of sunlight, low temperature, lack of growing space, or fungal diseases. I’ve written the details that can help you figure out what’s wrong with your tomato plants and what you can do about it.

Lack of Nitrogen

Nitrogen is the most essential macronutrient for the tomato plant to grow healthy foliage. If the soil is lacking in nitrogen, the tomato leaves will start falling off.

If you’re using soil rich in organic materials, it should contain a good amount of nitrogen. If it does not, then you need to amend it.

You can get the soil tested from your local extension service for a small fee. They will tell you exactly what is the problem in the soil and how you can fix it.

If you know the lack of nitrogen is causing problems to your tomato leaves, I would suggest adding a slow-release nitrogen-rich fertilizer to the soil.

This could be an organic fertilizer having high nitrogen content such as blood meal, bone meal, alfalfa meal, or kelp.

Make sure you add the amount as specified on the package. And you only need to add the fertilizer once every month or so. Make sure not to overuse the nitrogen fertilizer as it can burn the tomato plant roots and kill them.

Inadequate Sun Exposure

Tomatoes are a warm-season plant that needs at least 6-8 hours of sunlight every day. If the plant does not get this required light, it may start losing leaves.

You want to ensure that the tomato plant gets the required sunlight. So pick a spot in your garden that will get this.

Choose an open spot that’s free of shade-granting trees, fences, or tall structures. If possible, look for a planting spot on the southern side of your home.

South-facing walls experience the most exposure as the sun travels from the east horizon to the west. Thus, they’re perfect for plants like the tomato that need a lot of sunlight.

Exposure to Low Temperatures

The tomato is a warm-season plant that does well in temperature between 55 and 75 degrees Fahrenheit. If the temperature drops below 55 degrees, the plant leaves may start falling off.

At lower temperatures, the plant will go into conservation mode. The cooler environment triggers its survival response, forcing it to drop leaves as a last-ditch effort to stay alive. You’ll experience less foliage and a much smaller harvest at the end of the season.

Keep an eye on the weather report! If you’re scheduled to have nighttime temperatures any lower than 55 degrees, make preparations.

Protecting the plant isn’t like preventing frost damage. You’re looking at over-arching effects from simple air exposure. The goal is to keep soil and air temperatures around the plant stable.

If the tomatoes are in containers, bring them inside. Keep them on top of a heating pad or in a heated room. Outdoor plants will require a cover. Plastic covers can create a greenhouse effect to lift temperatures to a safer range.

Too Much Water

The tomato plants require lots of water but if you overwater them it can cause root rot. This fungal problem will damage roots causing a lack of nutrients to the leaves and they will fall off.

On average, tomatoes need one to two inches of water a week. Anything more than that, and you’re risking health problems.

Overwatering will cause the leaves to develop bumps and blisters. If you don’t scale back, they will wilt and eventually fall off.

This is a pretty easy problem to solve. Just ease back on the watering a bit! Every day check the moisture in the soil.

Stick your finger 1-2 inches in the soil and check if the tip of your finger feels moist. You should only water the soil if your finger feels dry.

Water the soil well so it gets a deep watering. This helps the roots spread deep into the soil to collect the moisture and nutrients.

As the temperatures rise, you may need to water twice a day to keep the plant well-hydrated. It prefers to live in moist soil. But, you don’t want to let the roots sit in standing water.

Not Enough Water

Tomato plants need a lot of water when growing into mature plants and developing foliage and tomatoes. If they do not get sufficient water, the leaves will start falling off.

Lack of water prevents the moisture and nutrients from the soil to reach the leaves through the roots. This lack of nutrients will cause the leaves to wilt and die.

The only way to tell if you’re underwatering your plants is to monitor their conditions. Pay close attention to the leaves in the morning. Usually, wilting early in the day is a telltale sign that the plant is deprived and thirsty.

The solution is the same as you would use when it’s a problem of overwatering. You need to monitor the soil every day and water as necessary.

Stick your finger 1-2 inches in the soil and check if the tip of your finger feels dry. That’s an indication you need to water the soil well.

One great way to get around a lack of water is to install a drip irrigation system. Drip systems will water the plant slowly and deeply, which is much more effective and helps you find that hydration balance.

Fungal or Bacterial Diseases

If the tomato plant gets infected by a fungal or bacterial disease, the plant will get stressed. One common sign of such stress is when the leaves start falling off.

Fungal diseases like Blight, Septoria Leaf Spot, Anthracnose, and more are quite common. Most of these diseases are either caused by fungus or bacteria.

Fungus-based diseases are usually a result of the growing conditions for the plant. Spores can also blow in from nearby infected plants, potentially ruining your entire garden.

The best course of action will depend entirely on the disease that’s plaguing your plant.

For fungal problems, the solution may be a change in the garden environment. Consider scaling back on your watering habits to prevent standing moisture. Avoid splashing water on the leaves when watering the plant.

You may also want to thin the plant out to increase air circulation and prevent ultra-humid environments conducive to mold growth. Some fungicides are available as well. They can keep many diseases at bay.

Now, bacteria-caused diseases are much harder to cure. Oftentimes, plants experience them due to contaminated soil or diseased foliage nearby. There’s no real cure for most bacterial diseases. Thus, the only solution is to eliminate the tomato plant and treat the soil to prevent future outbreaks.

Transplant Shock

You may have started tomato seeds or bought the seedlings. Once grown, you will transplant them outdoors. But this can cause transplant shock if you’re not careful. And the stress may cause the leaves to fall off.

A biological response, transplant shock occurs whenever you move the plant to a new environment. It could be moving the plant to a new container, an unfamiliar spot outside, or a garden bed in the ground.

If the environment is drastically different from what the plant is used to, it’ll experience various problems.

You must be very gentle when transplanting tomato plants. The first step is to choose the right time. Avoid transplanting on a bright and sunny day. Overcast days are best, as it gives the plant some time to adjust to more sun exposure or higher air temperatures.

You can also harden the plant off by building its exposure to its new home over the course of a week. Start by leaving it out there for an hour or two a day before it’s ready to live there full time.

When moving the plant to new soil, fertilize it first. The extra boost of nutrients will prime it for faster recovery, which may help you avoid the effects of shock.

There are many ways to avoid transplant shock. The trick is to be as gentle as possible and steer clear of exposing your tomato to extreme change all at once.

Not Enough Growing Space

The tomato plant can grow quite wide and need good space from the other plants. Lack of growing space causes problems like stress, lack of nutrients, and fungal diseases. All of these can cause leaves to drop off.

If the plants are too close to each other they start competing for nutrients and moisture. The lack of sunlight and air circulation between the plants can cause humid conditions attracting fungal diseases.

Tomatoes need 18 to 24 inches of space between them. If you are planting in containers, you’ll need to keep a single plant in a pot that’s at least 18 inches in diameter.

Carefully transplant your tomatoes to meet that space requirement. Thin the herd and make sure that air can flow between your plants freely.