Planter Boxes: 10 Tips for Growing Tomatoes

Growing Tomatoes Is a Favorite of U.S Homeowners

The U.S. is one of the top three gardening countries worldwide, with 71.5 million gardening households. And what do homeowners like to grow most? Tomatoes.

Tomatoes are the most popular homegrown produce, found in 86% of food gardens (RubyHome).

If you’re one of those households, these 10 expert tips will help you grow thriving tomatoes in containers.

1. Choose the Best Tomato Planter

Your tomato planter isn’t just a container—it’s your plant’s environment. The best planter box will help regulate moisture, prevent root rot, and support strong root growth. Whether you're gardening on a balcony or a backyard deck, the planter you choose directly impacts your yield.

Think of it as choosing the right home for your tomatoes: it needs space, drainage, and protection from the elements. Learn more about selecting the best tomato planter box.

What are the Best Materials for a Planter?

Wooden boxes are durable and have a natural look, but they can rot over time if not adequately treated. Moreover, some include treatments that can leach into your soil, impacting your plants.

Plastic planters are lightweight and easy to move, but they might not last as long in direct sunlight. To eliminate that concern, choose one that's UV-stabilized.

Metal planters look sleek, but they can scorch your plants on a hot day in full sun. That stresses your plants and means you'll likely have to water twice daily.

How Deep Should Your Tomato Planter Box Be?

Tomatoes need deep roots to grow strong and healthy plants, so choose a box at least 12-18 inches deep. The width should be wide enough to accommodate the plant without crowding its roots. Learn more about the best depth for planters.

Does Your Tomato Planter Need Drainage Holes

Drainage is another critical factor. Whatever gardening container you select must have drainage holes in the bottom. If not, drill several holes to prevent water from pooling. Otherwise, you risk root rot, which can kill your plants.

2. Choosing the Right Tomato Varieties for Containers

Not all tomatoes grow the same—and choosing the right variety is key when you're working with planter boxes. Some tomatoes stay compact and tidy, while others will sprawl and climb for weeks. The variety you choose will impact how much space you need, how often you harvest, and how much support your plants require.

If you're short on space or just starting, focus on varieties that are bred for container gardening.

Tomato Variety Comparison Chart

This comparison chart can help you choose the best tomato varieties for your container garden based on space, climate, and experience level.

Determinate vs. Indeterminate Tomato Varieties

Determinate varieties grow to a specific size, produce fruit, and stop growing. Also known as bush tomatoes, these are perfect for planter boxes because they stay compact.

Indeterminate varieties, on the other hand, keep growing and producing fruit throughout the season. This requires more space and support, as some varieties can reach up to 20 feet tall.

Heirloom vs. Hybrid Tomatoes – Which is Better

You'll also want to consider whether you prefer heirloom or hybrid varieties. Heirloom tomatoes have rich flavor and diversity, but can be less disease-resistant.

Hybrids typically resist common tomato problems and might be a better choice for beginners.

Choose Your Tomatoes Based on Climate

Finally, think about the local climate in your home garden. If you live in a cooler area, look for varieties that mature quickly. In warmer climates, choose heat-tolerant varieties that can withstand intense sunlight.

3. Use the Best Potting Mix for Tomatoes

Tomatoes grown in containers have one shot at good soil—so make it count. Unlike in-ground gardens, you can’t rely on natural soil biology or rainfall to balance things out. The potting mix you use will control drainage, airflow, and nutrient availability from day one.

The Best Soil Mix for Planters

Your potting soil is crucial for growing healthy tomatoes. A good blend usually includes Sphagnum peat moss and perlite or vermiculite to ensure proper aeration and drainage. You can buy a pre-made mix designed for container gardening or combine these elements to make your own.

Learn more about the right potting mix for containers.

How to Fertilize Your Container Tomatoes

Tomatoes are heavy feeders, requiring many nutrients to grow well and produce a bountiful harvest. Regular feeding is essential to keep your tomato plants healthy and productive throughout the growing season. Without enough nutrients, your plants might produce fewer fruits, which may be smaller or less flavorful.

Consequently, don't skimp on soil amendments during planting. Add dolomite and a balanced, granular fertilizer.

“A lot of gardeners underestimate how fast nutrients get used up in containers,” says Mark Bolt, Vice President of EarthBox, and a container gardening expert. “That’s why we include dolomite and fertilizer in our garden kits. It gives plants what they need without constant guesswork.”

4. Planting Techniques

When potting plants, you can start from seeds or seedlings. Starting from seeds gives you more variety of choices, but it takes longer and requires more attention. Small plants are a quicker way to start and are often more resilient.

Give Your Tomato Plants Plenty of Room

Tomato plants need space to grow, even in planter boxes. Plant each tomato at least 18-24 inches apart to give them enough room to spread out. Planting them too close together can lead to competition for nutrients and water, stunting growth.

Remember to Bury Your Young Plants Deep in the Soil

Equally important when planting, bury the tomato seedlings deeper than they were in their original pots. Tomatoes can grow roots along their stems, so planting them deeper helps establish a more robust root system. Snip off leaves several inches up the plant to ensure good depth.

Tomato Plants Require Staking

After planting, you'll also need to consider supporting your plants. Staking, caging, or using a trellis are all effective methods. They'll keep your tomatoes upright and prevent them from sprawling excessively.

5. Watering and Mulching

Watering is one of the most critical aspects of growing tomatoes in planter boxes. Tomatoes need consistent moisture, but avoid waterlogging the soil in your planter box.

Water your plants deeply and regularly, especially during dry spells. Inconsistent watering can lead to problems like blossom end rot or splitting tomatoes.

A Self-Watering Reservoir Maintains Moisture Levels

Self-watering planters are a fantastic solution for maintaining the proper moisture level. These planters have a built-in reservoir at the bottom that stores water. As plants grow, they can draw moisture as needed through capillary action.

“Using self-watering planters can reduce water usage by up to 60%,” says Mark Bolt, Vice President of EarthBox^®. “They also help prevent common issues like blossom end rot and splitting tomatoes. It’s the most efficient setup for container-grown tomatoes, especially in hot or dry climates.”

Self-watering planters maintain consistent moisture without daily effort. Your tomatoes get a steady water supply without the risk of overwatering or drying out. That’s especially beneficial during hot weather or busy schedules.

Learn why self-watering planters are a green thumb’s best friend.

Mulching Your Tomato Planters Helps Retain Moisture

Mulching is another excellent way to retain moisture in the soil and reduce watering frequency. Spread a layer of mulch, such as straw, grass clippings, or wood chips, around the base of your plants. This helps with moisture retention, stabilizes soil temperature, and prevents weeds.

Consider adding a drip irrigation system using traditional planters to maintain consistent moisture levels.

6. Feed Your Tomato Plants Regularly

As mentioned, tomatoes are hungry feeders, so fertilizing is critical to produce a sizeable crop.

Fertilizer Options for Tomato Plants

Tomatoes are heavy feeders, and container-grown plants rely entirely on you for nutrients. Choosing the right fertilizer—and using it at the right time—can mean the difference between a few small fruits and a season-long harvest. Here are your best options, whether you're going organic or conventional.

• Balanced Fertilizers: Start with a balanced fertilizer, such as a 7-7-7, 10-10-10, or 14-14-14 (N-P-K) formula. It provides equal amounts of nitrogen (N), phosphorus (P), and potassium (K). A balanced blend helps plant growth, root development, and fruit production.
• Tomato-Specific Fertilizers: Tomato-focused fertilizers often have a higher potassium (K) content to support fruiting. A standard ratio of 5-10-10 or 4-6-8 provides more phosphorus and potassium to promote blooming and fruit development.
• Organic Fertilizer: Compost, well-rotted manure, fish emulsion, or bone meal can be excellent nutrient sources for organic gardeners. Organic fertilizers release nutrients more slowly than synthetic ones, providing a steady food supply to your plants over time.

When to Apply Fertilizer to Your Tomatoes

Remember to add a slow-release fertilizer to the soil when planting. This will give your tomato plants a good start and provide essential nutrients.

During the initial growth phase, use a balanced fertilizer every 4-6 weeks to support leaf and root development.

Once your tomatoes flower, switch to a fertilizer higher in phosphorus and potassium. These nutrients encourage more flowers and fruits. Continue feeding every 2-3 weeks with a liquid fertilizer or according to the product's instructions.

How to Apply Fertilizer to Your Tomato Planters

For granular fertilizers, use them around the base of the plants. Gently work them into the top layer of soil, careful not to disturb the roots. Water the plants thoroughly after application to help dissolve the fertilizer and allow the nutrients to reach the roots.

For liquid fertilizers, mix according to the package instructions. Then, apply directly to the soil or as a foliar spray during regular watering. Spraying fish emulsion on your plants is also an excellent way to provide a boost.

Consistent feeding ensures that your tomato plants can access the nutrients they need to thrive. It helps ensure a generous yield of delicious, juicy tomatoes. Watch your plants for signs of nutrient deficiencies, such as yellowing leaves or poor fruit development. Adjust your feeding schedule or fertilizer type as needed.

7. Managing Pests and Diseases with Container Gardening

Even in planter boxes, tomatoes are vulnerable to pests and diseases. Common pests include aphids, hornworms, and whiteflies. You can manage them by regularly inspecting your plants and using organic pesticides. Simply spray your plants with water can dislodge pests like aphids.

Preventing Diseases with Container-Grown Tomatoes

Diseases like blight and root rot can also affect tomatoes in planter boxes. To prevent these, avoid overhead watering, which can create the damp conditions that diseases love. Instead, water the soil directly at the base of the plant. Rotating your crops yearly and cleaning your planter boxes at the end of the season can also help prevent disease buildup.

Best Solutions for Insect Control

Many natural solutions can help deter pests and diseases if you prefer organic gardening. Neem oil, insecticidal soaps, and companion planting with herbs like basil can keep your tomatoes healthy without harsh chemicals.

8. Harvesting Tips for Your Tomatoes

Harvesting tomatoes at the right time is critical to enjoying their full flavor. Tomatoes are ready to pick when fully colored and slightly soft to the touch. If unsure, you can also judge by the smell. A ripe tomato will have a rich, sweet aroma.

How to Harvest Your Container Tomatoes

When picking tomatoes, gently twist to avoid damaging the plant. If the tomatoes don't come off quickly, use garden scissors or pruners to snip them from the vine. After harvesting, store your tomatoes at room temperature, away from direct sunlight, to allow them to ripen fully.

9. Troubleshooting Common Issues with Your Tomato Garden

Even with the best care, you might encounter common issues when growing tomatoes in planting boxes.

What is Blossom End Rot?

Blossom end rot, for example, is a condition where the bottom of the tomato turns black and hollow. This condition often stems from calcium deficiency or inconsistent watering. To prevent it, ensure your plants are well-watered and consider adding calcium to the soil if needed.

How Can You Prevent Your Tomatoes from Cracking?

Tomatoes can also crack from irregular watering, especially after heavy rain following a dry spell. To prevent cracking, try to keep the soil consistently moist.

Why Are My Tomato Plants’ Leaves Turning Yellow?

Yellow leaves can indicate several issues, including nutrient deficiencies or overwatering. If you notice yellowing, check the soil moisture and consider adding a balanced fertilizer to boost your plants' nutrients.

10. Use a Tomato Planter Kit

Tomato planter kits are an excellent choice for growing tomatoes in planters.

Planter kits typically include everything you need to start, making it especially easy for novice gardeners. Planter kits from EarthBox, for example, include:

• Self-watering planter box
• A staking/trellis system with wire ties
• Wheels
• 7-7-7 fertilizer and natural dolomite
• Tomato & Veggie Boost
• Organic potting mix

“We designed the EarthBox system to take the guesswork out of growing tomatoes,” says Bolt. “With built-in self-watering features, the kit gives gardeners of any skill level a simple path to better harvests—no digging, weeding, or guesswork. Plus, you can grow tomatoes even with limited space.”

A tomato planter kit can remove the guesswork of setting up your planter box. That allows you to focus on caring for your plants and enjoying the process of growing your tomatoes. With end-of-season sales, the tomato planter kit solution costs as little as $118.99.

Why EarthBox is the #1 Solution for Growing Container Tomatoes

Growing tomatoes in planter boxes is a fun and rewarding experience, whether you're a seasoned gardener or just starting. To ensure your success, EarthBox is an industry-leading solution. Its tomato planting system and grow boxes are lab-tested for performance.

Ready to grow better tomatoes with less effort? Shop EarthBox planters and planter kits. Find the best planter box for your growing needs.

Happy gardening!