By Erin Marissa Russell
QUESTION: I want to grow tomatoes in a container garden. How deep should the containers be for cherry tomatoes and full-size tomatoes? — Allen Y.
ANSWER: The question of how deep the container for your tomatoes should be depends on the size of the mature plant. It doesn’t matter whether a plant produces large slicing tomatoes or cherry tomatoes. To determine how deep its container should be on the recommended spectrum, check into the mature size of the plant.
Containers for tomatoes should be at least between 24 and 36 inches. Miniature, patio, bush, or dwarf tomato plants can be planted in containers closer to 24 inches, while plants larger than three feet tall should be planted in deeper containers. Of course, you can plant tomatoes in even deeper containers without a problem.
There are a few other guidelines out there for the appropriate size of tomato for containers that don’t measure the container by depth. These guidelines measure the containers by diameter or volume. They may be easier to use in some situations, so we’ve listed them below.
- Plant determinate tomatoes in containers with at least an 18-inch diameter, and plant indeterminate tomatoes in containers with at least a 24-inch diameter. Not sure of the difference between determinate and indeterminate varieties? Check out this article on determinate and indeterminate tomatoes.
- Smaller tomato varieties, such as patio or bush tomatoes, should be planted in at least a 5-gallon or 10-gallon bucket. Larger varieties should be planted in at least a 20-gallon bucket.
Of course, if you start tomatoes from seeds, you will probably need to use seed-starting trays or another small temporary container while the plants are young. Raise them through the seedling stage in these small containers, then when it’s time to transplant the young tomato plants, you can move them to the larger recommended container sizes.
Some gardeners recommend planting tomatoes in especially wide containers. These gardeners say it isn’t only the depth of a container that’s important when it comes to growing tomatoes. Instead, they say that tomatoes have an especially wide zone where their roots are growing and will need the extra width to spread out in a container. For example, a large determinate tomato plant can have roots that extend up to two feet on either side of the plant.
Container size isn’t something you can skimp on as a gardener. The size of the container a plant is growing in has several different effects.
- As we’ve already discussed, roots can be confined by containers that are too small, which means that a plant will never see its full potential when it comes to the plant’s own size or health and the size of its harvest.
- Roots will suck all the moisture quickly out of a container that’s too small for a plant. Plants that are in containers too small for them may wilt or need to be watered multiple times each day.
- Blossom end rot is a plant disease that tends to strike plants that are malnourished and under-hydrated from containers too small for them. The disease causes tomatoes produced by the plant to turn black and leathery on the bottom and develop a flattened shape. Tomatoes affected by the disease may turn ripe too quickly and eventually rot.
If you suspect that the containers you’re using are too small for your tomato plants, they probably are. There’s no negative effect that comes from growing your plants in containers larger than they need, so when in doubt, we recommend scaling up. Some people are able to grow their tomatoes or other plants in containers that are too small most of the time without a problem. They may suddenly start seeing problems in seasons when the weather is more extreme as plants come under more climate-related stress.
If your tomato plants need to be moved into a container that will hold more soil, you may notice some of the effects we talked about in the last section. We’re talking about developing blossom end rot, wilting, sucking up water, or yielding small plants with small harvests. You may also be able to see the roots of the plant overlapping themselves in circles around the sides of the pot or at the bottom. This is a condition called a “rootbound” plant that means the plant’s roots are struggling to find more soil and more nutrition.
Now you know several guidelines to help you find the best size container for your tomatoes as well as several signs that a tomato plant needs a larger container. Just choose container sizes carefully, scale up when in doubt, and keep watch for these signs in your garden as your plants grow and their needed container size increases.