Container Gardening: Growing Tomato
Growing Tomatoes workshop at the Glendora Gardens Nursery. April 23, 2022.
One of my favorite crops from a kitchen garden is tomatoes. By garden, I don’t mean only raised beds or big yard. Tomatoes can also grow in containers. This is the topic we covered at our gardening workshop on April 23, 2022 at the Glendora Gardens Nursery: How to grow and take care of tomatoes in containers.
The goal of this workshop is to get people comfortable at the idea of growing food; that they can be successful in growing tomatoes in containers. And to prove “no green thumbs needed to garden!” What we all need is some basic knowledge related to growing tomatoes and time set aside to garden.
And I think we achieved that at the workshop! We all had fun. Everyone went home with a planter of tomatoes, goodie bag, and some even won the raffle prizes!
Winner! That tote looks so stylish :)
At the workshop we covered:
WHY CONTAINER GARDENING
TYPE OF CONTAINER & SOIL
TYPE OF TOMATOES
TRELLISING
TRANSPLANTING
PRUNING
WATERING
FERTILIZING
DISEASES & PESTS
COMPANION PLANTS
If you are looking for a list of resources and items mentioned/recommended at the workshop, scroll down to the end of the article.
OK. Let’s start from the top.
WHY CONTAINER GARDENING
Kitchen Mini Tomato in container. This type only grows up to 12” tall.
Container gardening is perfect for apartments, rentals, or homes with barely any gardening space, or say, the garden is paved or concrete. Growing in containers also means portability - it can be moved to an optimal location where the tomato plant gets 6-8 hours of sun, preferably most of the morning sun. In addition to sunlight, placing it in locations where water is easily accessed means watering becomes convenient. You’d less likely to forget or procrastinate watering it.
I will be first to admit, had it not for the drip irrigation system installed in my garden, everything I grow probably died already. I just have no time and patience to water every single one of them!
CONTAINER & SOIL
Rich organic potting mix of G&B and Fox Farms Ocean Forest in 7-gallons grow bags.
Tomato has a large root systems. It needs soil depth of at least 12”, and growing space of at least one square foot. In this workshop we are using a 7-gallon grow bag. I will not use any less for the reasons of nutrients deficiency and water evaporation.
Use container with good drainage. That means use pots with drain holes. No problem there with grow bags. On the flip side, the drainage concern could turn into dryness issue. We will cover that later below in WATERING.
The type of soil for container planting is important. The soil needs to have good drainage, aeration (not likely to get compacted), and rich in nutrients and organic materials (compost).
Use potting mix that is rich in composted organic matters. This can be either bought or a mix of your own. Potting mix is different than garden soil mix - garden soil is too heavy and usually have large chunks of matters. I would also advice against using existing soil you dug up from the garden, even if your garden soil is rich in nutrients, it will most likely carry in ground pests, such as pillbugs, slugs and other insects. While these usually don’t cause concern in a large raise beds or in the garden, in a small environment as in the container, they could fast become pest issues.
So save yourself some stress, and start with fresh soil.
TYPE OF TOMATOES
Basically there are two types of tomato plants:
DETERMINATE: Also called “bush” tomatoes. Grow to a fixed height (4-5’), produce its whole crop in one harvest.
Example: Roma, Amish Paste, Celebrity, Marglobe, Rutgers.INDETERMINATE: Also called “vining” tomatoes. Grow to at least 8’-10’ vine and will continue to grow until frost or diseases kill it. Producing a steady crops of tomatoes throughout the growing season.
Example: most heirlooms and cherry tomatoes..
Scroll down to RESOURCES for a list of Determinate and Indeterminate Tomatoes.
For container gardening, DETERMINATE types are suggested, as they are more compact in size and practically no pruning is needed. That doesn’t mean we can’t grow INDETERMINATE tomatoes in a container - we just need a bit more planning and care - which brings us to the next topic.
TRELLISING
Medium size obelisk trellis supporting cherry tomato (Indeterminate).
By nature, tomatoes grow sprawling on the ground. However, that increase the chance of pests ruining the crops and diseases infecting the plant. In controlled planting, which what farming or home gardening is, we use different types of trellis to support the growth of the tomatoes.
For DETERMINATE growing in a container, a tomato cage (circular or square) or a short obelisk trellis would suffice, as the plant only grow to a certain height.
Growing INDETERMINATE in a container is doable. It does need stronger, different type of trellis and more care - we will discuss this in PRUNING.
There are other methods to support growing tomatoes - single stem method using a rope or tall stake, ladder trellis, arch and panel trellis - these methods are typically used for INDETERMINATE tomatoes to support and control their continuous growth.
Since we are focusing on container growing, I will reserve the discussion on the trellising methods for another time. Let’s move on.
TRANSPLANTING
Workshop participants releasing root bound before transplanting.
The ideal time to transplant tomato to its permanent growing place is when the plant reach about 6-8” tall. Depending on the nursery pot it comes in, typically anything taller usually the plant already has developed root bound.
Root bound is when the roots has grown in a circular pattern following the confined space of the pot. It will stunt the growth of the plant. Here’s what to do when we encounter root bound:
Water the seedling to make sure the soil in the pot is thoroughly moist. Take out the seedlings out of the pot. Carefully loosen up the root ball. Tease out the roots so the ends are free from its circular growth pattern. Discard the tangled roots as necessary. This will help the roots to grow naturally after being transplanted, ensuring strong and healthy growth of the plant.
If the plant is extremely root bound, the process or unbounding will cause trauma to the root system. Tomato is resilient, but a small help from B1 FERTILIZER will further reduce transplant shock.
Dig a hole so the seedling can be planted 1” deeper than the original soil line. Or in the case of a tall seedling (12” or taller), plant it much deeper - remove leaves or any growth that get buried. Deep planting forces the plant to grow more roots from the buried part of the stem. And more roots means more nutrients that can be absorbed by the plant, which resulted in a healthier and stronger plant.
While typically not necessary for container gardening - as we already use rich potting mix - adding a sprinkle of powdered egg shells in the hole where the tomato is transplanted will help prevent “blossom end rot” - this affect the fruits where the bottom is flat and brown due to lack of calcium.
How much is a sprinkle? I’d estimate my “sprinkling” to be a bout 1 tsp per hole. Too much then the calcium could impeded the plant’s ability to absorb magnesium from the ground.
PRUNING
The practice of keeping the bottom 12” of the plants free of leaves is to conserve the plant’s resources to the blossoms and fruits production. It also helps with ground air circulation, which minimize fungal diseases.
For DETERMINATE, barely any pruning is needed. Mainly to prune off leaves that grow inward - again, to improve air circulation and allow pollinators to find the blossoms.
For INDETERMINATE - except cherry types - in addition to inward leaves pruning, regularly pinching off suckers will focus the plants energy to the main vine for more blossoms and fruits.
Suckers are new vine growths from the base of the leaves. Left alone this growth will form a “new main” vine that will also produce fruits.
Keeping the number of “main” vines to a minimum typically yield larger fruits and stronger and healthier plants. It’s because the energy is more focused than spread out to a lot of vines. If not doing a single stem method, I like to keep 3 main vines from the suckers that grow closest to the base of the plant.
When growing INDETERMINATE tomato in a container, it is crucial to keep the growth of the vine under control. Cap off the plant when it has reached over the cage. As for pruning off suckers, your call. For larger fruits, but less harvest, keep the main vines to a minimum (4 at the most).
Unpruned tomatoes or letting the suckers growing unchecked would either yield more fruits but smaller, or more leaves than fruits.
Neglected Indeterminate tomato. It is growing well with healthy soil, but barely any fruits.
WATERING
Tomato needs consistent watering. Do not wait until the soil is completely dry to water. Total dehydration will cause stress to the plant as well as making it prone to diseases and pests attack. Oh yes. Those pests? They can sense weak plants!
A split or crack on a tomato caused by extreme change in temperature and or inconsistent watering.
Have you seen tomatoes with crack lines? A drastic change in temperature or inconsistent watering (or both) will cause tomato’s skin to expand and contract, resulting in splits. Not appealing, but still edible. Although the cracks, while still not scabbing or dry, could be an easy entry point for pests! That is one more reason we want to keep watering consistent, and protect the plants from heat waves.
In anticipation of a heat wave, provide covering or shade for the plant if possible and water the plant extra in the morning. For frost, well, tomatoes are not supposed to grow beyond frost, unless they are growing in a greenhouse. As for cold spells, as long as the temperature still hovering around 50s F, tomatoes can withstand the chill.
Soil in containers especially in grow bags will dry out faster than soil in a large raised bed or out in the garden. If there is no automatic irrigation for the container, I recommend using some type of water reservoir to supplement regular watering, in case the weather turns very hot and dry, or when we forgot watering the plant.
Unglazed terracotta watering stake is my favorite reservoir tool. Use it with a long neck bottle filled with water (wine bottle), and the container has a lifeline for at least a day or two (when I forgot to water it or go out of town for a weekend).
In addition to a reservoir, mulching will help reduce water evaporation.
Watering stake used in Herb Container Gardening Workshop.
FERTILIZING
Tomatoes are hungry plants! They use up a lot of nutrients from the soil. The best practice to fertilize them is “little & often”. Every 2 weeks is a good frequency for feeding the plants.
On the fertilizer bag, search for 3 numbers separated by dash lines “X-X-X”. The numbers refers to the N-P-K composition of the fertilizer.
Use fertilizer that has higher number of Phosphorous - the one with higher middle (“P”) number. Phosphorous encourages blossoms production, which translate to more fruits. You will find me using fertilizer with higher Nitrogen content (“N”) in the beginning - Nitrogen promotes leaves production and speed up growth. When the plant is about 2’ tall, I switch to more P & K numbers.
Or to make it simpler, just grab a bag that’s labeled Tomato Fertilizer.
DISEASES AND PEST
Common diseases with tomatoes are:
Powdery Mildew - looks like powder all over the leaves.
Early Blight - looks like white blotches on the stems.
Septoria Leaf Spot - dark spots on the leaves, usually starts on the lower leaves.
Common pests:
Spider Mites - leaves turning yellowish with white speckles all over, fine webbing and tiny red insects (spider mites) on the underside of the leaves. In bad infestation, you will see webbing over the plant.
Aphids - greens or white tiny globular insects. Some have wings.
Hornworms - Hard to spot unless you are really looking! They are green with 7-diagonal lines and a horn on their butt (hence, hornworm)
Cabbage Loopers - green and crawling like a drunk caterpillar.
My “go to” spray to address the above issues is a mixture of the following:
Neem oil - Coat the plants to deter insects to lay eggs, kill mites, pests, fungus, and mildew. Used correctly it will not harm beneficial insects and birds.
Peppermint Castile Soap - The scent will repel flying insects. Works on sugar ants as well.
Tea Tree Castile Soap - Disinfect the plant, cleansing and kill egg sacks and larvae of mites.
Hydrogen Peroxide 1% - Take care of mildew and mold. Also kill pest insects.
Isoprophyl Alcohol 70% - Destroy the mites web structure so the spray can get through to the egg sacks. Disinfect the plant.
Luke Warm Water - Keeping the neem oil in its liquid state. Neem will solidify when the temperature drop (just like coconut oil).
SPRAY RECIPE
I got the original recipe from the Liquidirt channel on YouTube. Then modify it to add Neem oil for added adherence.
2 Quarts of Luke Warm Water
1 TSP Neem Oil
0.25 Cup Peppermint Castile Soap
0.25 Cup Tea Tree Castile Soap
1 Cup Alcohol 70%
1 TSP Hydrogen Peroxide 1%
If you only have 3% Hydrogen Peroxide, dilute it with water or use 1/3 tsp of it.
Use up what you mix on the same day as the potency of the mix will drop (alcohol and hydrogen peroxide).
TOMATO COMPANION PLANTS
French Marigolds are one of the best and most common companion plants. Not only they are beneficial to deter pests, the flowers come in many different color!
Companion plants are planted in close proximity or in the same container as the crop plants for the purpose of:
Pest Deterrent
Attract Beneficial Insects
Flavor Enhancing
Promote Growth
In a large planting space, we can plant multiple companion plants and practice polyculture. In a container, however, space for root growth is limited. We do not want the companions to compete with the crop plant for nutrients. If there is space, limit to planting just 1 companion plant that has small root system, such as:
Nasturtiums - Deter aphids, whiteflies, squash bugs, beetles, ward off fungal diseases. This is my favorite. The flowers and leaves are edible. They are water hungry though and needs to be in partial sun.
French Marigolds - Repel nematodes, tomato hornworm, slugs.
Chives - Repel aphids
Garlic - Repel Spider Mites
Some companion plants are better to be planted in nearby separate containers. These plants deter pests or serve as bait plants, attracting pests away from the crop plant.
Mint (perennial herb) - Deters white cabbage moths, ants, rodents, flea beetles, fleas, aphids.
Parsley (biennial herb) - Attracts hoverflies (which feast on tomato pests).
Borage (annual herb) - Repels tomato hornworm, cabbage worm. When planted in the same container, improves the flavor of the tomato.
Basil (annual herb) - Repels whiteflies, mosquitoes, spider mites, aphids, hornworms. When planted in the same container, improves the flavor of the tomato.
Fennel (annual herb) - Attracts ladybugs
Cilantro (annual herb) - Attract ladybugs and lacewings. Pollinators’ favorite especially when bolted (flowering). I purposely plant this through the year for the later reason.
Companion planting also make your kitchen garden more attractive and pleasing to look at with combinations of flowers and different leaves textures.
Overall, a healthy plant is the best defense against pests and diseases. Sometimes, despite our best practices of consistent watering, regular fertilizing, and pruning that should take care of the plant’s health, nature might throw a curve ball at us. Never get discourage. I see gardening as a constant play with food while learning at the same time. Find the fun in the process and enjoy the outdoor :)
Happy gardening!
Catharina ‘Kat’ is a Gardenary Certified Kitchen Garden Consultant serving the greater Los Angeles, San Gabriel Valley Areas.
Kat started Blissful Growing in 2021 with the goal of helping others living a healthier and sustainable lifestyle starting with growing food at home.
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RESOURCES & LINKS
Some of the links below are Amazon affiliate links. None of the products are sponsored. These are recommendations based on personal use and from other trusted sources.
Unglazed Terracotta Watering Stakes
Blood Meal (High Nitrogen fertilizer)
List of Determinate (bush) Tomatoes
