Tomato plants growing in a pot or container have a unique water requirement than the plant growing in the ground. The two most common questions asked by balcony gardeners and first-time gardeners are: How much water does a tomato plant need per day? And how often should tomato plants be watered?
Let me answer each question in detail.
How often do tomato plants need to be watered for the tomato plant growing in a pot?
The watering frequency depends upon the size of the container, weather condition, and the type of tomato growing in the pot. A bush type tomato growing in a 5-gallon container needs water every day, sometimes twice a day during the hot summer months, and when the plant is actively producing tomatoes.
The best way to check if the plant needs water is to stick your finger in the potting mix up to 2” deep. If the soil feels dry, it’s time to water. Drooping leaves are the clear visual sign that the plant is thirsty.
If you see your tomato plant leaves turning yellow, it could be a sign that the plant’s watering requirements are not met.
Another convenient alternative is to invest in a Soil Moisture Meter. Just stick the prong in the soil, and the dial will show you the moisture amount in the potting soil. It is the easiest way to measure the water level in the pot accurately.
Okay, now that you established the tomato plant needs water, you wonder how much to water!
How much water does a tomato plant need per day?
A large, well-established tomato plant in a pot needs about a gallon of water a day. The size of the container, the daytime temperature, and the growing stage of the tomato plant may affect the amount of water the plant needs. As a general rule of thumb, water the container slowly until water comes out of the drainage holes at the bottom.
Factors to consider when watering a Tomato plant in a pot:
As mentioned above, many factors affect the watering needs of potted tomato plants. Here is the summery of the factors affecting the watering frequency of the potted tomato plant.
| Factor | Less Frequent Watering | More Frequent Watering |
|---|---|---|
| Container Size | Large (bigger than 15 gallon), Deep | Small (less than 14”), Shallow |
| Container Material | Plastic, Resin | Clay, Metal |
| Container Color | White and light colors | Black and other dark colors |
| Tomato Type | Patio and determinate varieties | Indeterminate and vining varieties |
| Weather | Spring and fall, cool temperature | Summer, hot temperature |
| Location of the pot | Shaded from the afternoon sun, away from the wind | Directly in the sun all day, in the path of wind |
| Quality of potting soil | Higher moss and clay | Sandy and porous |
| Stage of tomato Growth | Seedling, young plant, at the end of the season | Actively producing new fruits |
Let me explain each one in detail:
Size, material, and color of the tomato planter:
The size of the pot is one of the most significant factors that impact the watering requirements of the tomato plant. Tomato roots can go as deep as 20” if they have the room. When confined by the space, the roots start to grow at the periphery of the container and make the plant ‘root bound’. Being root- bound impedes the ability of the plant to absorb water and nutrients out of the soil and can stun the growth of the plant.
When growing tomatoes in bucket or pots, the bigger the container, the better. Plan to get the container at least 14” wide and 14” deep. Another option is to make a 5 gallon bucket tomato planter. For more prominent vining type or indeterminate tomatoes, 20″ pot like this or bigger pot size is recommended. You may get by with a smaller container size if you are more diligent in watering and fertilizing routine.
Other than the container size, pay attention to the material and color of the pot as well.
Containers made of clay will evaporate the water much quicker than those made of other materials. Resin containers are better for growing tomatoes.
The color of the pot also plays a part in retaining water. Black and other darker colors get hotter much quicker and lose more water through evaporation than lighter colors.
Ideal containers for growing tomatoes:
Tomato Type:
The second most significant factor to consider is the type and variety of tomato that you are growing in the pot. Take the time to know what type of tomato you are growing.
Indeterminate tomatoes (for example- San Marzano, Cherokee Purple) and vining kind of cherry tomatoes grow 6’ or taller. These large plants need more water to sustain leaf and fruit development.
Small patio type tomatoes are dwarf varieties that grow up to 1’ to 3’ tall. They have a moderate amount of water needs. If planted in a bigger container, watering can be reduced to every other day.
Weather:
Weather is a prominent influencer to watering needs of a tomato plant in pot. The hotter the temperature gets, the more water the tomato plant needs. During summer months, you may have to check the soil twice in a day to make sure the potted tomato is not running out of the moisture. In early spring and late fall, because of the lower temperatures, the watering can be done every other day.
Location of the pot:
Just like growing tomatoes in your garden in a raised bed, it matters where you put the potted tomato in your balcony or patio. When the pot is in the full sun or in the path of wind all day, more moisture will evaporate through tomato leaves, and you will have to water the plant more frequently.
If the pot receives the additional watering through rain, wait to water again until the top 1” to 2” of soil dries out.
An indoor tomato planter may not need frequent watering because of the less exposure to the wind and sun.
Quality of the potting soil:
The sandy or porous soil has less water holding capacity. Most of the water drains out quickly, which requires more frequent watering.
The clay type or heavy soil retains water much longer and requires less regular watering.
Best potting mix for tomatoes should have enough organic material like peat moss and compost to hold the water long enough for the root to absorb without being too waterlogged.
Stage of Tomato growth:
Just like the humans, the watering needs of the tomato plant in container changes as it grows. The small seedlings or newly transplanted tomato plant requires less amount of water then the tomato plant actively producing fruits.
One tip I learned from the local master gardener is, holding the water back a little when the tomato fruits are almost ripe intensifies the tomato flavor!
Importance of regular watering of tomato plant:
Did you know that the tomato is made of 93% of water? That’s why it is extremely crucial to provide consistent water to the tomato plant to grow optimally and produce an abundance of juicy tomatoes.
Inconsistent watering causes two physiological deformations in tomato plants:
Blossom End Rot:
When the potting soil is too dry or too wet, it affects the tomato plant’s ability to absorb the calcium from the soil. This kind of drastic variations in soil moisture level causes the bottom of the tomato fruits to deform and look like the dark, rotten part. It is essential to maintain a steady moisture level in the soil to prevent the Blossom End Rot.
Fruit Cracking:
Though the cracked tomatoes are okay to consume, it is unsightly. When the thirsty tomato plant suddenly receives too much water, the sudden surge of water makes the fruits to expand more quickly than their skin can grow. This results in split or cracked tomatoes. (According to NC State University Cooperative Extension)
The best way to prevent this is to harvest the almost ready tomato fruits ahead of rainfall, even if it means they finish ripening on the kitchen countertop than on the plant.
Best Practices for Watering potted tomato plant:
1. Check the soil every day
Don’t assume that you water the pot recently, so it is okay to skip the day. Scratch the soil 2” deep. If the soil feels dry, the plant needs water. Plus, as an added benefit, regularly checking the tomato plant will help spot the trouble spots, signs, and pest before it becomes a big deal (Check out how to make a DIY natural pesticide, if you do get pests on your tomato plant).
2. Water deeply
Give a thorough drink every time you water. The top 6” of soil should be moist after each watering. It will encourage the roots to go deeper and stronger.
3. Water slowly
Don’t just dump a jug of water in the pot. Provide a slow stream water so the potting soil have enough time to absorb the water before the water drains out.
Investing in a quality drip irrigation system for container, along with the timer is one of the best investment you can do for your container garden. It puts the watering on auto pilot and provides slow, deep watering at a scheduled interval.
4. Don’t over-water
Providing too much water is just as bad as not providing enough water. The root of the tomato plant starts to rot in the wet environment. Give enough time between watering. Make sure the soil is not wet before the next watering. Use a Soil Moisture Meter to check if the soil needs water.
5. Make sure the overflow water drains out
Another common rookie mistake is to forget to cut holes in the bottom of the container. The excess water that the soil receives needs a way to drain out of the pot. As mentioned above, wet soil is not suitable for tomato plant roots.
6. Line the bottom of the container
Line the bottom of the pot with a layer of coffee filters of a large piece of weed block fabric . It will prevent the potting soil from draining out along with the water.
7. Mulch the pot
To reduce the watering frequency, it is a good idea to layer an inch or two of wood chips or hay on top of the potting soil. Mulching will prevent the water from evaporating from the soil and retain moisture for the long term.
8. Water at the base of the plant
Avoid watering from the top and wetting the leaves. It causes diseases to spread from one leaf to another.
9. Water in the morning
Many of the tomato pests are attracted to the water droplets attached to the leaves. Watering in the morning gives enough time for the leaves to dry out before night, which will save the plant from the pests.
10. Cut back on watering when the fruits are nearly ripe
It is a natural way of hastening the tomato ripening process. Lack of water signals the tomato plant to divert the plant energy towards the fruits than towards the other part of the plant. Some gardeners believe that this helps to intensify the tomato flavor as well.
Conclusion:
Tomato plant is consisting of 90 to 93% of water. It is essential to water the potted tomato plant regularly and consistently. Following the above watering guidelines will help you grow a healthy, productive, and disease-free tomato plant in a pot.
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Last updated: 4/10/2021
Great article. I have container tomatoes, did well, set great fruit. I added large 2” deep saucers under container to keep water available. Now no new fruit and blossoms die and fall off. Do I need more miriacle gro or remove saucers cause too much water