Caroline Lewis is a Portland, Oregon, urban gardener whose company, Verdura Culinary Gardens, is dedicated to helping gardeners be more successful at raising their own organic vegetables. A licensed landscape contractor, Verdura installs raised bed gardens including trellises and drip irrigation systems, creates custom year-round planting plans, and offers vegetable garden coaching and maintenance programs. Caroline welcomes your comments and can be reached at caroline [at]

Tomato tips

Growing tomatoes in a cool climate

August 18, 2011

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 the past two 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 varietals 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 Farms, tries to stick with varietals that mature in 80 days or fewer. Gales Meadow Farms lists many varietals that they’ve have grown successfully over the years in Washington County, Oregon.

Secondly, think about growing smaller tomatoes. In our nearly disastrous season last year, only one tomato succeeded nearly everywhere we planted it: Sun Gold, a lovely little orange-yellow cherry tomato with intense flavor.

Sun Golds ripen early.

This year, we’ve planted Sun Gold in almost all of the 32 gardens we manage. It is reliable, productive, and the earliest tomato we harvest. So in planning for your garden next spring, 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 (i.e., vining) varietals, requiring trellises, cages, or other vertical supports to grow. Using the right supports not only makes better use of your 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 — each 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 and made of much heavier wire. Ours have lasted for years.

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.

Prune suckers.

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.

Tomatoes are the most popular crop among her clients.

Prune the roots

Seriously. It works! Last 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 to 8 inches from the trunk, 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.

We plan to root-prune this year’s tomatoes in a couple of weeks in each of the gardens we manage. Between that, some judicious pruning of suckers, and a prayer for a continuation of our current glorious summer weather, we’re hoping to beat the odds and produce a healthy crop of ripe tomatoes this season.

There are 9 comments on this item
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1. by anonymous on Aug 18, 2011 at 11:42 AM PDT

So glad I read your tip about root pruning. I’ve got blight on my tomatoes.. so I’m pruning off dead leaves and tomatoes every day, praying that some of them will ripen in time. As soon as they gt close I take them off and let them ripen inside, to avoid them getting blight. there are tons of good size tomatoes out there, so i’m going to root prune each plant.. let it ripen those ones quickly before they all get blight. thanks so much.

2. by Lisamary Wichowski on Aug 18, 2011 at 8:55 PM PDT

Thanks Caroline. Forwarding this to my fellow gardeners in our community garden in Portland. Out of 28 plots we’ve had 5 ripe tomatoes so far this year!

3. by a pdx gardener on Aug 20, 2011 at 8:20 AM PDT

We have late blight. The plants aren’t too sick, with most branches still healthy, and the fruits look good. But as soon as the fruits start to ripen, those mottled dark patches appear on them.

Is it possible that we could save any of our tomatoes? Can they really fully ripen, without blight, if picked green? What I’m wondering is if we should pick all the unblemished (but very green) tomatoes and then rip out the plants. Or is it possible the plants could overcome blight?

4. by anonymous on Aug 20, 2011 at 9:41 AM PDT

to pdx gardener - the only way to stop blight is fungucide - copper spray.. but then your garden is not natural.. so i opted out. you can make green tomato chutney, soon as they show any color you can take them off and they will ripen.. i’m doing that daily and still getting some nice tomatoes. I ripped out the plants with really dark stems.. keeping the ones who only have it on their leaves, and keep eye on them and rip out brown instantly.. since i’m doing it diligently, it is spreading slower.

5. by Caroline Lewis on Aug 24, 2011 at 3:28 PM PDT

Ugh, late blight definitely can be an issue. We usually rip out plants when we realize we have it, as there’s no way to stop it and it spreads to other, healthy plants. Worse, the longer you leave plants in place, the more likely you are to have it next year. So I would pull off the healthy green tomatoes and get those plants out of there. Do NOT put them in your compost - they’ll have to go in the trash. Green tomatoes will ripen on your kitchen counter but they’ll never have as much flavor as vine-ripened tomatoes. Try chutneys or pickles, as suggested above, or slow-roast counter-ripened tomatoes with olive oil, garlic and herbs to concentrate their flavors.

6. by anonymous on Aug 24, 2011 at 6:38 PM PDT

Hog wire panels make great sturdy trellises. Can’t say enough about using row covers or hoop houses. People around here will cover up their plants at night starting in August to collect as much night time heat as possible so that the tomatoes set and ripen.

7. by anonymous on Aug 31, 2011 at 10:01 PM PDT

What about watering? In addition to heavy pruning it seems like scaling back on the watering significantly helps my tomatoes to ripen sometimes a month earlier than most home gardeners I know.

8. by Caroline Lewis on Sep 21, 2011 at 1:05 PM PDT

Yes, absolutely. We aren’t watering them at all at this point in the season.

9. by Richard Yarnell on Dec 28, 2011 at 2:52 PM PST

A couple or three comments about growing tomatoes in Oregon. I’m making the assumption that most readers will be growing small gardens.

1) Start your plants as early as you can in a protected place. I don’t mess around transplanting to successively larger pots. Start with gallons and leave the plants in them until you can safely set them out in your garden.

2) Your intent is to have a leggy plant, just the main stem, up to 18” tall at the time of transplanting. When you do plant them in the garden, dig a trench and lay the tomato on its side, turning up the growing end just enough to have the top exposed. You should have trimmed all the foliage off the plant up to about the last six inches. You’ll end up with a trench that’s full of roots since the plant will spontaneously root along its entire length. You’ll have a vigorous plant supported by a large root structure. (If you put the plant into a patio pot, trim the foliage and then bury the plant to the very bottom of the pot.) Your soil should be well structured and light. I use rabbit manure which doesn’t have to be composted. We also keep chickens and a mule. Those droppings should be composted.

3) I plant indeterminates almost exclusively. I grow them under a “trellis” formed on 12’ t-posts topped with pvc hoops. Those hoops spread a plastic sheet to form a shelter to keep our liquid sunshine from falling on the plants. Most tomato diseases are soil born. If you can keep the soil from splashing onto the plants, you’ll find they stay healthy much later. To support the plants, I tie them as the grow to heavy twine that’s suspended from the trellis. The pruning advice is good - necessary in the way I train the plants. I aim to have two leaders from each plant.

I use “road fabric” as a ground cover. It’s durable and will last several seasons. I don’t put any organic material on top of the ground cover. Before I lay it out, I install a drip irrigation system along the entire length of the furrow in which I plant. Not only does it save water, is easily and inexpensively controlled by a timer, it completely eliminates irrigation water splashing up into the foliage, spreading disease.

Until I had to tear out my trellis system to make room for a house we started building almost 4 years ago, I replanted in the same area for four years running and had no disease at all. I hadn’t intended to do that, but the second year I got caught short of time and replanted. When the plants were disease free and productive until the first hard freeze, I decided to see how far I could push it. Normally, one wouldn’t replant tomatoes, eggplant, or potatoes in the same place, year over year.

Finally, when you find a variety that you like and that thrives where you live, save some seed. From a dead ripe fruit, take the seed, rinse it, and then “ferment” it in a small container of fresh water. The object is to remove the gelatinous coat that surrounds the seed. Rinse the seed and change the water every day until the seed is free. Lay it out on a paper towel and let it dry thoroughly. Once it’s dry, fold it into a pouch made from paper, label it, and put it in a small glass jar. I keep up to a hundred seeds of each variety, plant from the previous year’s seeds, but keep the surplus for a year or two against an emergency. I’ve had very high germination rates from seed that was four years old. The seed should be stored in a cool, dark, place. Some people freeze the seed so long as it is well dried. I have yet to try that trick.

As to the root trimming trick, that certainly works. But since I’ve got long trenches filled with roots, I prefer simply cutting back on the water to induce ripening. With the drip system and the sheltered planting area, the plants get only the water I give them.

Two other points: I don’t compost any solanaceous plants. If you do have a disease in your potatoes, tomatoes, or egg plant, the chances are, you’ll spread it throughout your garden. It’s not worth the risk.

When you do end up at the end of the season with lots of green tomatoes, chutney, fried tomatoes and gravy, pickles all come to mind. But during the season when the fruit is still ripening, do your morning tomatoes, bacon and gravy with ripe fruit. You’ll like it a lot. Remember that using the green fruit is a compromise: the object is to not waste the still unripe fruit.

Beavercreek at 1150 feet when the growing season starts a month later than it does in Portland.

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