Container Gardening: 5 Tips for Growing Tomatoes

Tomatoes growing in a dark green EarthBox container gardening system

Tomatoes have a lot going for themselves. First, there’s the obvious – they’re downright tasty. Second, they’re loaded with lycopene, a powerful antioxidant. Third, they support heart health with anti-inflammatory properties. And fourth, they’re easy to grow in gardening containers.

If you’re already growing tomatoes in containers, you probably have a pretty good idea about how to get the biggest harvest. But if you’re new to container gardening, here are some tips for growing tomatoes to get you off on the right foot.

And hey, even some of you more experienced container gardeners may learn a thing or two!

Tip #1: Select Tomato Varieties Suited for Container Gardening

It’s hard to believe, but there are more than 15,000 tomato varieties globally. They break out into determinate and indeterminate types.

Determinate tomatoes (bush or patio tomatoes) set their flowers, and produce fruit in a single flush, generally for one to two weeks. Typically, they’re compact, topping out at five feet.

Indeterminate tomato varieties, on the other hand, continue to grow fruit over the entire growing season once they mature and until frost. However, they also require more room and a support system because they grow larger, six feet high or more.

So, your first step is determining which you want to grow. Owing to their smaller size and fewer sprawling concerns, determinate tomatoes readily thrive in gardening containers.

That’s not to say you can’t grow indeterminate varieties in planting boxes. But it’s slightly more challenging. You’ll need to provide more soil and a solid support structure.

Top Container Tomato Varieties

Some top bush tomato varieties for container gardening include:

  • Celebration
  • Italian Roma
  • Glacier
  • Tiny Tim
  • Patio Choice
  • Heirloom Stupice
  • Tasmanian Chocolate
  • Litt’l Bites
  • Inca Jewels
  • Tumbler
  • Early Girl
  • Bush Steak

Top indeterminate varieties include:

  • Sungold
  • Black Cherry
  • Sun Sugar
  • Bumblebee
  • Carmello
  • Stupice
  • Brandywine
  • Sweet 100
  • Sweet Baby Girl

Make sure you know which type by reading the plant label or asking someone at the garden center. Otherwise, your tomato plant could quickly consume your space.

Tip #2: Think Big When Selecting a Gardening Container

Here’s a common mistake people make growing tomatoes in containers. They select tomato planters that are too small. Tomatoes have an expansive root system, so always think larger versus smaller.

Twelve inches is the minimum depth for tomato planters. And, as you might have guessed, you’ll need an even larger planting box to house an indeterminate tomato plant.

So aim for a gardening container at least 18 inches long and 12 inches deep. If you prefer to think in terms of gallons, select at least a 10-gallon container for indeterminate tomatoes. That’s the minimum, but consider a 20-gallon container to help your plants thrive.

A good starting point for determinate types is three gallons. But you can’t go wrong if you err on the larger side with at least seven gallons and as much as ten gallons.

The bottom line is that size counts when growing tomatoes in planters. You’ll need that size to avoid drying your soil out too quickly. Dry soil reduces the fruit production of tomatoes.

Additionally, you might want to avoid black gardening containers, as they can absorb heat. That accelerates soil drying rapidly and creates heat that can impact plants’ roots. For instance, tomato plants like their roots to be cool.

Tip #3: Focus on Good Watering Habits

That may seem like a no-brainer, but you’d be surprised how many people routinely fail to water their tomato plants. It’s essential to keep the container’s soil moist.

That becomes especially critical in July and August when it’s the hottest. Often, it requires watering your plants twice a day. Remember, tomato planters dry out more quickly than in-ground soil.

Insufficient moisture causes tomato plants to wilt. But, more importantly, it can lead to blossom end rot (BER), which creates sunken, brown spots on the fruit’s bottom.

Water the Soil, Not the Plant

Directing the water onto the soil, not the plant’s leaves, is equally essential. Unfortunately, many gardeners water from overhead, creating two issues.

First, only some of the water reaches the soil. So, even if you think you’ve thoroughly watered your plants, the soil may not be as moist as needed.

Second, the leaf moisture creates a breeding ground for fungi spores to germinate and infect your plants. The longer the leaves remain wet, the more likely you’ll have a disease problem.

Invest in a Self-Watering System

There is a solution if you aren’t confident in your watering skills. You can purchase a sub-irrigated planter box that removes the guesswork from watering.

For example, EarthBox planting boxes include a water reservoir. Add water daily to the fill tube until water flows from the drain. The plant’s roots can then access a ready supply of water.

You can fill the water reservoir in the morning and later on hot summer days.

Tip #4: Don’t Skimp on the Fertilizer

Tomatoes are heavy feeders, meaning they need a steady supply of nutrients for the best yields. So get them off to a good start by adding a slow-release fertilizer, like Osmocote, to your gardening container when you plant.

After planting, you’ll need to replace those nutrients routinely, typically after five or six weeks. First, the tomato plants will consume them. And second, some nutrients will drain from the container with excess water.

A good rule of thumb for fertilizing tomato planters in containers is doing it a little more often versus a lot less often. That helps to retain a constant nutrient supply.

You can use a water-soluble fertilizer. Just mix a small amount of balanced fertilizer into water.

Selecting a Fertilizer

For the most part, a balanced fertilizer with equal amounts of nitrogen, phosphorous, and potassium will do the trick. For example, a standard 7-7-7 mixture works well for almost any plant.

You can determine whether you’re over-fertilizing if your plants produce more leaves than fruits. Conversely, you’re likely under-feeding if the foliage turns yellow.

With fruit plants, phosphorus is essential. It encourages flowering, which increases the yield and ripening of the fruits. Consequently, consider using a fertilizer with added phosphorous (the middle number). For example, bone is an excellent organic source of phosphorous with an analysis of 4-12-0.

Avoid nitrogen-based fertilizers as they’ll produce abundant leaves but have little impact on fruit production.

Remember to always follow the manufacturer's recommendations. For example, you should not use a time-release (e.g. Osmocote) or water-soluble fertilizer in the EarthBox container gardening system.

Tip #5: Don’t Cook Your Tomato Plants

It’s essential to keep your plants’ roots cool. Studies show root growth slows or stops when soil temperatures reach 86 degrees Fahrenheit. The roots die when soil temperatures reach 96 degrees or more.

High soil temperatures are more of a concern with container gardening. So when outside temperatures climb, keeping plant roots cool is critical.

As mentioned, black gardening containers absorb heat and can cause roots to bake. So lean toward lighter-colored planters to keep roots cooler.

One of the benefits of container gardening is that you can relocate plants. So, take advantage of that.

Instead of having your tomato plants bake in the midday sun, move them to a more shaded spot. You can make the job easier by getting wheels on your gardening container.

For example, you can add a caster kit to EarthBox planting boxes for only $10.00.

If moving your containers isn’t your cup of tea, at the very least, make sure you add a thick layer of mulch or other organic material. It helps retain moisture while keeping your plants’ roots cool.

EarthBox Tomato Planters Come with a 100% Guarantee.

If you want to enjoy the benefits of container gardening, check out the offering of EarthBox planting boxes. They’ve been tested in laboratories and shown to double the yield of conventional gardens. And with much less work.

There’s no digging, weeding, or guesswork. You can even get a tomato-growing kit that includes everything you need:

  • Planting box
  • Mulch cover
  • Staking system
  • Wire ties
  • Casters
  • Fertilizer
  • Organic potting mix
  • Tomato & Veggie Boost calcium nitrate supplement (to prevent BER)

The sub-irrigated planting box ensures your plants get the proper water amount daily. So even if you don’t have a green thumb, you can grow and harvest your very own tomatoes.

Tomatoes, carrots, and herbs being grown in different EarthBox gardening containers