Carol O’Meara is the horticultural extension agent in Boulder county. She has decided to find out for herself if growing tomatoes upside-down works in our climate, and is sharing the ongoing results of her experiment on her blog, Gardening After Five. She brings up a number of important issues; reading her article is a good place to start.
Of course, we won’t know how successful Carol is until the end of the season. In the meantime, we do know a bit about growing tomatoes in containers. Here are a few points to keep in mind.
Make sure your container has good drainage. The upside-down growing bags automatically drain out the bottom, solving this problem.
Match the plant size to the container. Big tomatoes need huge pots. Since these bags are relatively small, stick to the smaller tomato cultivars, such as Bush Early Girl, Stupice, Siberian, Early Wonder, or Red Robin (a very dwarfed variety). There are so many varieties to choose from, you’ll need to ask about the choices at your local garden center.
Use a commercial or homemade potting mix, rather than soil. Soil becomes overly wet and compacted in containers, and roots die from lack of air. Any brand of soilless mix will do. If it doesn’t already have fertilizer in it, you’ll need to add some.
Much of the Colorado Springs area is higher than Boulder, so we need to use every minute of our short growing season. First, choose the earliest (shortest “days to maturity”) variety you can find. Then, place your plant in a protected spot, away from chilling winds and hail. This can be tricky, since tomatoes need full sun as well. Sometimes plastic can help. Try wrapping a tube of plastic sheeting around your container plant, leaving the top open so overheated air can escape.
Bury your plant up to the first leaves, but no deeper. Your seedling needs every leaf surface it has to make food for rapid growth.
Containers dry out quickly, and need constant monitoring. Be sure to keep the potting mix damp (but not saturated) at all times. Tomatoes are not drought-resistant.
If your plant has flowers but doesn’t set fruit, pollination may be an issue. Purchase “tomato blossom set spray” at a garden center and apply it to your flowers. This hormone will fool them into growing fruit. As a bonus, often the resulting tomatoes have no seeds.
Following package directions, add additional fertilizer when fruit starts to form.
Be on the alert for tomato hornworms, and pick them off if they appear. (These tomato pests are the larval form of the Hummingbird moth.) Soap sprays control aphids and whiteflies. Early blight (a common problem in our area) is unlikely if new, sterile potting mix is used.
If you had success growing upside-down tomatoes last year, we’d love to hear from you. What tips to you have for the rest of us? Did your crop fail? We’d like to hear about that too.
Article and photo by Leslie Holzmann, Certified Colorado Gardener.