Friday, September 25, 2009

Tomatoes in Containers

It took me a while to warm up to the idea of growing tomatoes in containers, but once I did, I kind of fell in love with it. Containers have definite advantages ... the biggest one, of course, is that you completely control the soil environment, so there's no soil-borne pests or diseases. If you want to grow the exotic heirlooms and beefsteaks, containers make it easy.

That said, there are drawbacks to containers. They tip over, especially near the end of the season when your vines are heavy with fruit. But you know what they say about planning ahead ... set up your containers right the first time, and you'll only have to worry about this if a hurricane hits. In which case tomatoes will be least of your problems.

Also, containers will need to be watered more frequently (at least daily by the end of the season), and every so often, you'll have to flush the container to remove accumulated fertilizer salts.

Container Soil

In some ways, it's easier to deal with the dirt issue in containers because, one way or another, you have to provide it. First off, you can grow excellent tomatoes in a bagged soil mix. Just pick up a few big bags and you're good to go. Once again, avoid mixes with moisture retention crystals or you risk ruining your harvest.

Or you can blend your own soil mix. Here's mine:
  • 2 parts sphagnum peat
  • 2 parts compost
  • 1-1.5 parts perlite
  • dolomite lime (1/2-cup per 5 gallons)
  • bone meal and blood meal
This mix provides macro- and micronutrients from the compost and the amendments of bone and blood meal. It is, however, deficient in potassium, so I will be using a general organic fertilizer throughout the season. As a rule, I try to keep my grow as organic as possible, so I like to build a strong soil with lots of good, organic nutrients.

If you aren't concerned with organic tomatoes, you could skip the compost and the bone and blood meals and add a high-quality controlled-release fertilizer like Osmocote, along with some micronutrient powder, and you'd have a very complete, fast-draining mix. Or you could skip any added fertilizer at all (but not the lime!) and just feed your tomatoes throughout the season. Some of this depends on your skill level with growing in containers and some on your preferences.

Later, I'll get into more depth on organic fertilizers versus synthetic fertilizers and feeding tomatoes in general.

Tips for Container Culture

When you're setting up your containers, here are a few ways to help ensure success:
  1. Go big. Use at least 10 gallon containers, if not bigger. Your tomatoes will grow as large as the container allows, and you want big plants, right? Also, the bigger the container, the heavier it is, so it'll be less likely to tip over.
  2. Make room for staking. I've seen a few ways to stake up container-grown tomatoes. You can build a cage around the container—which will displace the tomatoes' weight to outside the container—or you can install the cage in the container and anchor it to the ground. More on staking up tomatoes later, but for now, make sure you've got room for it.
  3. Don't bother with drainage material in the bottom of the container. I've caught a lot of grief for this recommendation, but it's true. Container grown plants don't need drainage substrate in the bottom, and in fact, don't want it. In every soil medium—the ground, a potted plant—there is a level at which the soil's "wicking" ability to suck water upward (think about a paper towel dipped in water) balances the downward gravitational pull. This is called the perched water table. Below the perched water table, the soil is saturated with water, which can suffocate plant roots and encourage root rot. Above this level is usable soil. By adding a gravel substrate, instead of increasing drainage, you're actually moving the perched water table UP in the container, so the plant has even less room to grow. In other words, skip the rocks.
  4. Get new soil. Don't grow tomatoes in last year's soil, or in soil that has previously grown peppers of any variety or eggplants. Two reasons: the soil becomes exhausted and there is increased chance of disease.
Up Next: Tomatoes and the EarthBox ...


  1. R. Johnston of KeyPlex here. Consider using a foliar applied micronutrient such as KeyPlex HG on your tomatoes. The reason I mention this is because there are many times that the micro's in the soils can become "bound" and unable to be used by the plants. You can get a 32 oz. bottle with hose-end sprayer at KeyPlex Direct.

    Don't get me wrong. Use the soil mix and granular fertilizer (time released) but a few weeks to a month after planting go ahead and hit them with the foliar minors and see what happens.

  2. We moved to south Fl from Ohio and we bought a tomato plant in a larger pot with a cage already. I have 6 tomatoes growing but I notice the leaves towards bottom are turning yellow and the leavins are wilting. I've only had the plant for a week. I hope it won't die. It is getting morning and evening sun where I have it but wonder if it is still too hot? Up in Ohio it was usually cool, the sun was never so strong like it is down here and they grew wonderfully. So what should I do? Any help would be appreicated. We bought this plant at Sam's club. I just bought a green pepper plant as far that one is doing OK and has one marble size pepper growing so I'm excited about that :)

  3. Melody,

    Welcome to South Florida! Now comes the bad news ... it's very difficult to grow tomatoes and peppers in SoFla in the summer. Our tomato season is just ending, not starting. We typically plant in October or November and harvest throughout the winter months. By now, with the heat just beginning and the rain around the corner, very few vegetables can survive. It actually kind of frustrates me that a lot of big box stores are still selling vegetables—they're almost certainly doomed.

    That said, since you've already got the plants, I would definitely use some kind of preventive spray for fungal diseases (like copper fungicide perhaps) and watch them carefully.