Growing Tomatoes in a Cool Climate
May 27, 2013 at 5:26 AM
With relatively cool, short growing seasons, the Pacific Northwest is a challenging place to grow tomatoes. When we get a particularly wet and cool spring and summer, as we have in several recent years, it gets even trickier. Yet, tomatoes are a wildly popular fruit and are by far the most-requested crop we grow for our clients.
Here are a few things we’ve learned over the years about growing tomatoes that may help gardeners in any climate, particularly one with a short season.
Choose your varieties wisely
Everyone loves those huge, gnarly heirloom tomatoes like Paul Robeson or Mortgage Lifter on display at the farmers market. They are wonderful, but it can be really difficult to get them to ripen in time to harvest before cold weather sets in. So consider alternatives when you’re planning your next garden. Our grower Annie Berblinger of Gales Meadow Farm tries to stick with varietals that mature in 80 days or fewer. The above link to the GMF site lists many varietals Annie and René have grown successfully over the years on their farm in Gales Creek, OR, located in the cool foothills of the Cascade Range.
Secondly, think about growing smaller tomatoes. In our nearly disastrous season two years ago, only one tomato succeeded nearly everywhere we planted it: Sun Gold, a lovely little orange-yellow cherry tomato with intense flavor.
Ever since, we’ve planted Sun Gold in almost all of the 30+ gardens we manage each season. It is reliable, productive and the earliest tomato we harvest. So if you haven't already planted your tomatoes this season, make sure to consider Sun Gold or other cherry or grape tomatoes, or even shorter-season (smaller) heirloom tomatoes as an option.
Use the right plant supports
Nearly all heirloom and many other tomatoes are indeterminate – or vining – varietals, requiring trellises, cages or other vertical supports to grow. Using the right supports not only better utilizes available garden space, it keeps plants healthier and allows more sunlight and air to reach the fruit. Vertical growing keeps plants up off the ground and away from pests like slugs. And it helps the fruit ripen earlier and more consistently on the vine.
There’s a reason those ubiquitous galvanized wire tomato cages are inexpensive. They’re flimsy and, if you think about it, rather poorly designed. As the season progresses and tomato plants grow tall and heavy, the cages – a series of connected concentric rings that are smaller in diameter at the bottom – eventually tip over.
We far prefer to use either square folding cages, our own copper or galvanized steel trellises or Sturdy Cages made by Oregon Wire Products. Sold under the brand name Cascade Green, these cages are the inverse of the traditional design, with a wider, stable base. They are powder coated (making them resistant to rusting as well as attractive) and made of much heavier wire. Ours have lasted for years. Although Oregon Wire Products doesn’t sell directly to the public, we have seen their Sturdy Cages and folding cages at numerous local garden centers including Portland Nursery, Garden Fever! and Al’s Garden Center.
Prune tomato plants as they grow
Indeterminate tomato plants can get huge in a hurry. They grow tall – often 5 or 6 feet – and send out numerous suckers, which make the plant quite bushy if left unchecked. These suckers are branches that form at the intersection of the main stems and what I’ll call “true” branches. Although the suckers will eventually flower, pruning some of them off throughout the season allows the plant to put its energy into its main branches and fruit, improving the size of the remaining fruit as well as the speed at which it ripens. Pruning also helps shape the plant and encourages vertical growth.
The photo here shows a sucker being pruned off a trellised tomato at the intersection of one of the plant’s main stems and a young branch. We do this early in the season, as we transplant the young plants to their raised beds. We continue to prune off suckers every few weeks throughout the season.
We try not to overdo it, though – leaving some suckers means more leaves to provide energy to the ripening fruit. After a few pruning sessions, we focus on pruning only to shape the plants and keep them more or less contained within their cages or their allotted space on the trellis.
Are your tomato plants already sprawling out of control? If so, or if you’d just like to see more examples of how and where to prune those suckers, check out this great video we found on the blog, Maria’s Farm Country Kitchen. It shows how an experienced gardener tackles an overgrown, sprawling tomato, prunes off suckers and trains the plant to grow on a simple bamboo support he builds.
Prune the roots of the plant
Seriously. It works! Several years ago in August, when we started to panic a little about our many still-green tomatoes, we saw a reader’s tip in an article by Kym Pokorny. A little additional research confirmed her reader’s suggestion that we cut the plant’s roots, so we gave it a try in our own garden. A few weeks later, we did the same in most of our clients’ gardens.
Using a pruning saw or other long, sharp implement, we cut straight down into the soil about 6-8” from the main plant stem, cutting a semi-circle around one side of the plant. Sounds cruel, perhaps, but it doesn’t hurt the plants at all. It seems to shock them a little, though, apparently letting them know it’s time to ripen the fruit. Within two or three weeks, they do just that.
Since then, we have continued to root-prune many tomato plants in gardens we manage. Between that, some judicious pruning of suckers, and a prayer for some glorious summer weather, we’re hoping to beat the odds and produce a healthy crop of ripe tomatoes this season.