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Your Indispensable Guide to Growing Tomatoes in Portland

Tomatoes! Tomatoes! Tomatoes!

Tomatoes are a favorite crop for gardeners everywhere. One of my all time favorite gardening quotes comes from public radio show host Mike McGrath:

“Everybody wants to grow tomatoes. Tomatoes are the gateway drug to all kinds of gardening.”

Spring has sprung full force in Portland. Our amazing 7-day and beyond forecast is full of sunshine. The forecast is for daytime high temperatures in the 60s to low 70s and nighttime lows in the 40s. May is a few short days away and by now I know you are itching to fill up your edible garden for a summer harvest.

While it is especially tempting to plant your tomatoes this week, I assure you it is still too early to plant tomatoes. Tomatoes need much warmer temperatures and if they are planted prematurely they will be come stunted, stressed, and not bounce back.

Here are my top tips for successful tomato gardening in the Portland metro area:

--Tomatoes like warm weather. They require night temperatures consistently above 55 degrees. In Portland this is typically between May 15-June 1st. Don’t plant tomatoes to early!!

--Tomatoes like warm soil. They need soil temperatures consistently of 60 degrees.

--Plant your tomatoes into the garden by transplants/starts. Portland does not have a long enough or hot enough summer to facilitate direct seeding tomatoes. If you want to start your tomatoes by seed you do so inside during February.

--Purchase the largest healthiest looking plants. If the plants have flowers or even small tomatoes on them at time of purchase, pinch these off. We want our tomato plants to initially focus on root, stem, and leaf growth before setting flowers and fruit.

--Tomatoes require a full sun location, ideally south facing, where they receive 8-10 hours of direct sunlight per day. Tomato plants will not set fruit in shady areas.

--Tomatoes are “heavy feeders” and appreciate being planted with an organic granular fertilizer, which will slow release for about 30 days. Continue to sprinkle fertilizer on top of the soil around your tomato plants on 30 day intervals May through September.

--Tomatoes are prone to blossom end rot. To prevent the disease blossom end rot, add an organic calcium source into the planting hole, such as a spoonful each or lime and bone meal or rock phosphate. You will find these in the fertilizer section of your local nursery.

--Tomatoes have very long root systems around 3-4 feet deep. Make sure they are planted in ground soil that is amended with compost, loose, and light for their roots to thrive. If growing tomatoes in a raised bed or container ensure it is deep enough.

--Tomatoes are big plants and need proper spacing to thrive. Don’t crowd them! Give tomato plants at least 4 feet wide between plants.

--Tomatoes can be grown in large containers. Use a 5 to 15 gallon size pot filled with organic potting soil, not ground soil or raised bed mix. Select a container variety such as: sweet baby girl, patio princess, stupid, balcony, baxter's bush cherry.

--Tomatoes need support. They have dense branches laden with heavy fruit. Install a sturdy tomato cage, the larger the better, at planting time to prevent later damage to your plant.

--Established tomato plants do not need a lot of water. Be consistent with a deep watering a few times a week throughout the growing season. Inconsistent watering contributes to fruit splitting and blossom end rot. Remember, newly planted tomatoes will need more watering than established plant, especially if it is hot and sunny.

--Tomato plants take several months to produce in Portland. Expect your harvest to begin in late August for slicing and saucing varieties and in July for cherry varieties. Your tomato harvest will be over in October when cold temperatures set in.

--Rotate your crops. Do not grow tomatoes in the same place every year as it contributes to disease and pest problems. Use a 4-year rotation for the entire tomato family that also includes potatoes, peppers, and eggplant.

--Determinate vs indeterminate varieties. Tomato varieties that are determinate, typically sauce/paste types, grow to one size and produce all their tomatoes at the same time for harvest at the same time. Tomato varieties that are indeterminate, most cherry and slicing types, continue to grow and set fruit for harvest throughout the growing season.

--Select varieties with days to maturity under 80 days. Our summer growing season in Portland is short with mild day and night temperatures. The larger beefsteak varieties with days to maturity 90-100 will not have time to ripen in our climate.

There is a seemingly endless selection of tomato varieties. Some of my favorite varieties for both taste and reliable harvest in Portland are:

Cherries: sungold, matt’s wild cherry, yellow pear

Slicers: lemon boy, ananas noire, costoluto genovese/florentino, black krim, green zebra

Sauce/Paste, san marzano, amish paste

If you want to learn more about growing tomatoes and other summer vegetable crops please join me this Saturday May 4 for Warm Season Vegetable Crops.

Happy Planting,


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