Tomatoes 101

Hey Garden Besties!

Let’s talk about tomatoes. Tomatoes are one of the most common crops people think about growing when they start their gardening journey. While some people say tomatoes are “easy to grow,” I personally think they can be a little tricky, especially if you are new to gardening.

Before you start worrying about every possible tomato problem, it helps to understand the basics first. What type of tomato are you growing? How much space does it need? Does it need support? How should you fertilize it? And can you grow it in a raised bed or container?

In this post, we are going to keep it simple and focus on the foundation of growing tomatoes.

You can grow tomatoes from seed or buy nursery transplants. Both work, but for beginners, I usually recommend starting with transplants first. Seed starting can be tricky, and I do not want that part to discourage you before you even get to growing.

Starting from seed is helpful when outdoor temperatures are still too cold, but you want to give your tomatoes a head start. This is especially useful for gardeners with shorter growing seasons, like zones 3, 4, 5, and some parts of zone 6.

If you start from seed, begin indoors about 8 to 10 weeks before your last frost date. Tomatoes germinate best with warmth, so a heat mat can help, but it is not required.

If you buy transplants, check the plant label before purchasing. Look for the variety name, whether it is determinate or indeterminate, days to maturity, and any listed disease resistance.

One of the first things to know is whether your tomato plant is determinate or indeterminate. This matters because it affects how the plant grows, how much space it needs, and how much support it will require.

Determinate tomatoes are often called bush tomatoes. They grow to a set height and then slow down or stop growing. Most determinate tomatoes stay more compact, often around 3 to 5 feet tall depending on the variety. They usually produce most of their fruit in a shorter window of time, which is helpful if you want to harvest a lot at once for sauces, canning, or meal prep. Determinate tomatoes are usually better for containers and smaller spaces, but they still benefit from support. A tomato cage or sturdy stake can help keep the plant upright once it starts holding fruit.

Examples include:

Indeterminate tomatoes are vining tomatoes. They continue growing and producing throughout the season until heat, disease, frost, or the end of the season slows them down. These plants can easily reach 6 feet or taller, so they need strong support from the beginning. A small tomato cage usually is not enough for a healthy indeterminate tomato. Indeterminate tomatoes also benefit from light pruning, especially removing lower leaves that touch the soil and thinning some growth to improve airflow.

Examples include:

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Once you understand the difference between determinate and indeterminate tomatoes, the next thing to know is the type of tomato variety you are growing. You may see words like heirloom, hybrid, open-pollinated, or F1 hybrid on seed packets or plant tags. These terms can feel confusing at first, but they are important because they help you understand flavor, disease resistance, seed saving, and what to expect from the plant.

Heirloom tomatoes are varieties that have been grown, saved, and passed down for many years, often at least 50 years. This does not mean the individual tomato plant is 50 years old. It means the variety itself has been preserved over time by gardeners, farmers, families, or seed savers. Heirloom tomatoes are often loved for their flavor, colors, shapes, and history. They may be red, purple, yellow, green, striped, large, small, smooth, or oddly shaped. Many gardeners grow heirlooms because they want tomatoes with unique flavor and personality.

One thing to know is that heirlooms may not always have the same disease resistance as some newer hybrid varieties. That does not mean you should not grow them, but it does mean you may need to pay closer attention to spacing, airflow, watering, and plant health.

Many heirloom tomatoes are also open-pollinated.

Open-pollinated means the plant can be pollinated naturally by wind, bees, butterflies, or other insects. If you save seeds from an open-pollinated tomato and grow them again, the next plant will usually grow true to type as long as it was not cross-pollinated with another tomato variety nearby. In simple terms, open-pollinated tomatoes are a good option if you are interested in seed saving. For example, if you grow an open-pollinated tomato and save the seeds, you can usually grow that same variety again next season. This is one reason many gardeners love heirloom and open-pollinated tomatoes.

Hybrid tomatoes are created by intentionally crossing two different parent tomato varieties to bring out specific traits, such as better disease resistance, higher production, more uniform fruit, improved heat tolerance, or stronger growth.

This is not the same thing as a GMO tomato. Hybrids are created through traditional plant breeding, which is controlled cross-pollination. This is a method that has been used for many years to develop many of the fruits and vegetables we grow today. GMO crops are created using genetic engineering technology to change the plant’s DNA in a lab setting, which is different from traditional cross-breeding. I think this is important to mention because there is a lot of misinformation around hybrid seeds. Some people hear “hybrid” and assume it means the plant is GMO or cannot be grown organically, but hybrid does not automatically mean GMO.

You may also see hybrid tomatoes labeled as F1 hybrids. This means they are the first generation from that specific cross. Just keep in mind that if you save seeds from a hybrid tomato, the next plant may not grow exactly like the original.

A few examples of hybrid tomatoes include:

Celebrity
Early Girl
Better Boy
Heatmaster

Hybrid tomatoes can be a great choice for beginner gardeners because many are bred to be productive, reliable, and more resistant to certain common tomato diseases. One of the reasons there are so many hybrid tomato varieties is because plant breeders are often trying to solve common growing challenges, like disease pressure, heat tolerance, fruit quality, or overall plant performance. This can be especially helpful if you garden in a warm, humid climate where tomatoes are more likely to deal with fungal and bacterial issues. Just remember, disease-resistant does not mean disease-proof, but it can give your plants a better chance when combined with proper spacing, watering, and airflow.

Spacing is important because tomatoes need airflow. When tomato plants are too close together, the leaves stay crowded, airflow is reduced, and fungal issues can spread more easily.

If you are growing in containers, plant one tomato plant per container. A 5-gallon container can work for small patio tomatoes, but for larger tomato plants, I prefer a 10 to 15-gallon container or larger. If you are adding companion plants like basil, marigolds, onions, or garlic, plant them around the tomato without crowding the base of the plant. Companion planting can be helpful, but overcrowding can create more pest and disease issues.

Pruning tomatoes can help improve airflow, keep the plant easier to manage, and reduce leaves touching the soil. This is especially helpful in warm and humid climates where crowded plants are more likely to deal with fungal issues. Before pruning, it helps to know if you are growing a determinate or indeterminate tomato because they should not be pruned the same way.

A tomato sucker is the small shoot that grows in the “V” where the main stem and a leaf branch meet. Those suckers can eventually turn into more stems, flowers, and fruit, so you do not always need to remove every single one.

With determinate tomatoes, only prune when needed. Focus on removing leaves that are touching the soil, yellowing, damaged, or showing signs of disease. The goal is not to shape the plant heavily. The goal is simply to keep the plant healthy and reduce leaves sitting on the soil where disease can spread.

For indeterminate tomatoes, pruning is more helpful because these plants continue growing and producing throughout the season. Since they keep sending out new growth, they can quickly become crowded if they are not managed.

With indeterminate tomatoes, you can remove lower leaves, thin out crowded areas, and remove some suckers to help improve airflow and keep the plant easier to support. You do not need to remove every sucker, especially as a beginner. Start with light pruning and focus on growth that is making the plant too crowded, touching the soil, or making it harder to trellis.

The main goal with pruning is not to strip the plant down. Tomato leaves help the plant make energy and can also help protect fruit from sunscald. Try to avoid pruning when the plant is wet because that can make it easier to spread disease.

Tomatoes are heavy feeders, so they need nutrients throughout the growing season. The biggest thing to remember is that tomatoes need different support at different stages of growth.

When the plant is young, you want to support strong roots and healthy leaf growth. Once the plant starts flowering and fruiting, you do not want to overdo nitrogen. Too much nitrogen can give you a beautiful leafy plant with very little fruit.

This is why fertilizers labeled for tomatoes and vegetables can be a great option. Many of them are formulated to support fruiting plants and may include calcium, which helps support strong cell walls and healthy fruit development. Calcium is also important because a lack of available calcium in the developing fruit can contribute to issues like blossom end rot. My favorite at the moment is the True Organic Tomato and Vegetable Fertilizer.

Just remember, calcium is only one part of the picture. Tomatoes also need consistent watering because even if calcium is present in the soil, the plant needs steady moisture to move that calcium into the fruit.

Always follow the product label because every fertilizer is different. A soil test is also helpful, especially if you are growing in the ground or if you have been using the same raised bed or container soil for a while. It helps you understand what your soil actually needs instead of guessing.

For this example, I am using a 4-foot by 4-foot raised bed. You can get creative with your layout and adjust it based on your space, but the key things to remember are spacing, airflow, and companion planting.

When you first plant tomatoes, think about the mature size of the plant. A tiny transplant may look small in the bed at first, but tomatoes grow quickly. Give the plant enough space from the beginning so it is not crowded later.

For this example, let’s say we are planting indeterminate tomatoes.

When growing tomatoes in containers, many of the same rules apply. The most important things are container size, soil quality, consistent watering, and choosing the right tomato variety.

For containers, I recommend starting with determinate tomatoes because they usually stay more compact. A 5-gallon container is the minimum size I would use for a small patio tomato. For larger tomato plants, I prefer a 10 to 15-gallon container or larger. If you want to add companion plants, you have a few options. In a larger container, you can plant one small companion plant with the tomato, like basil or a marigold. You can also plant companions in smaller separate containers and place them near your tomato plant.

Container-friendly bush tomato varieties:

Patio – classic container tomato bred for pots
Bush Early Girl – early harvest with compact growth
Celebrity – reliable producer and semi-determinate
Roma – great for sauces and canning; look for determinate types

Tomatoes are not always as simple as people make them seem, but once you understand the basics, they become a lot easier to manage. Start by knowing what type of tomato you are growing. Give it enough space, choose the right container or garden layout, support it early, and fertilize it consistently.

In the next post, we will talk about some of the most common tomato issues that can impact your plants and harvest. Happy Gardening!