Wondering When to Plant Tomatoes in Pacific Northwest? Not as Soon as You Want To!

by Georgie Smith, farmergeorgiewrites@gmail.com

Sunny days in the tomato patch

The moment those first few warm sunny days of April burn off the winter doldrums, Pacific Northwest gardeners begin dreaming of the “Holy Grail” of the summer garden – home-grown, vine-ripened tomatoes. 

Nothing screams summer as much as a luscious, garden tomato, ripened to a glowing red (or yellow, purple and even green!) hue, just waiting to be picked. 

Heirloom tomatoes come in all the colors of the rainbow!

Yet how often do home gardeners rush out in mid-April (or even early April!) for those first of the season tomato plants from the crowded aisles of the mega garden centers, pop them with great anticipation into their too-cool spring garden soils, only to be met a few days later with a sad, shriveled and dying tomato plant? Plants that may recover, but never really go on to the produce the promised tomato bonanza?

If there is one thing to remember about growing tomatoes in the Pacific Northwest, it’s this – Just Wait Already! Best temperatures for growing tomatoes are between 55 and 85 degrees, with soil temperatures at 50 degrees or above. And, folks, that doesn’t happen in April!

While temperatures into the 30s will likely just kill your plant outright, even temperatures in the 40s will cause a lot of problems. Tomato blossoms will drop when temps dip under 50 degrees, and nothing sadder to see all your potential fruit littering the soil below your plant! And then, even when temperatures finally warm up, tomatoes planted much too early will show the detrimental effects of that for weeks after. Plants that experienced under 50-degree temperature for four to five weeks before flowering, will often produce misshapen or cat-faced fruit. http://www.omafra.gov.on.ca/english/crops/facts/info_tomtemp.htm

And remember, even if you grow in a plastic-covered or glass greenhouse where day-time temperatures warm up nicely with a little sunshine…your night-time temperatures will plummet down quickly! (Unless you are providing supplemental heat). A 60-degree day in the sun may easily be 80 to 90 degrees in a greenhouse, but once the sun goes down and it gets down to 45 degrees for a low, your greenhouse will get that low too! 

Greenhouses provide extra heat for tomatoes…BUT…they get just as cold in the evening time!

The average low temperature for data collected in Bellingham between 1985-2015 was 41 degrees for the month of April. May low temperatures averaged 46 degrees and finally, in June, we break the barrier and reach an average of 51 degrees for low temps.  https://www.timeanddate.com/weather/usa/bellingham/climate

This is why even commercial tomato growers in the Pacific Northwest will carefully monitor their tomato plantings making sure to wait til moderate, warmer night-time temperatures are the norm before planting into unheated greenhouses OR providing supplemental heat for earlier plantings they want to get an extra push on.

So now, that you have resisted the urge to plant those tomatoes and it is the perfect planting window of mid-May to early June… what are the best home-gardener tips for selecting great tomato plants for a healthy summer harvest?

Eight Easy Tips for Home Growing Tomatoes In the Pacific Northwest

#1 – Buy Local Tomato Plants!

Choosing varieties adapted for cooler growing climates is where buying your plants from a small, independent nursery or garden center (versus the big box stores) will really reap dividends. The big box stores get the same tomato varieties for all their stores, and we all know that tomato growing in the cool Pacific Northwest is a much different scenario than the hot summer climate of the Midwest. Local independent garden centers will usually only stock regionally suitable varieties AND their staff will generally be able to provide you with much more regional growing information as well.  

#2 – Choose Tomato Plants that are BIG

Chose local-grown, robust tomato plants!

 Pick large, stocky (but not gangly) tomato plants grown indoors in a heated environment. Look ideally for plants with lots of flower buds or blossoms, but not a lot of fruit set yet. If you do choose a plant with fruit, snipping off those initial small fruits may seem painful, but it will result in a more vigorous, productive plant that will reward with you a larger harvest. 

#3 – Extra Heat For Tomato Plants Helps

Provide supplemental heat to start – just in case! Certainly, planting into a greenhouse is the easiest way to do this. But you can still create temporary, ‘mini-greenhouses’ to use around your plants when they are small with a little extra care and creativity. The traditional ‘Wall of Water’ is probably the easiest to use. But you can also make them yourself….http://www.homemadetoast.com/2014/05/diy-wall-of-water.html

#4 – Plant Tomatoes in a Warm Location

Find a sunny, but protected area in your garden to plant. Tomatoes do like full sun, but the most important thing is to provide your tomato with HEAT. A partial sun yet warm, protected spot on a porch is better than a full-sun, but windy and cold drafty location!

#5 – Plant Tomatoes in a Shallow Trench

When it’s time to plant, dig a shallow trench about one inch deeper than the root ball and plant your tomato ‘sideways.’ Don’t be afraid to remove bottom leaves so you can plant a larger portion of stem into the ground. This does two things: You have now planted into the top layer of your soil which will generally be warmer than if you dug down deeper AND the tomato plant will grow roots all along that stem you put into the soil, creating a strong and more resiliently-rooted base for your vigorously growing plant. https://shawnacoronado.com/how-to-plant-a-tomato-with-a-trench-technique/

#6 – Tomato Plant Pruning and Proper Support

Pruning and tying up indeterminate tomato plants

Have a plan for pruning and managing your tomato’s explosive growth! This will vary depending on if you have a determinate tomato plant (shorter, stockier plants that don’t tend to vine much – oftentimes wire tomato hoops will work for these varieties). Versus an indeterminate tomato plant (very vigorous, vining plants that will need frequent pruning and support throughout their growth period). But don’t be afraid to PRUNE to fewer vines. An un-pruned plant will set so much fruit it doesn’t have energy to put into ripening, and all that green leafy foliage is a magnet for dampness and shade which can lead to disease. So PRUNE.  

Farmer Mark demonstrates how to prune your tomatoes!

#7 – Tomato Plant Fertilizing

Mix in a high-nitrogen, all-natural fertilizer at planting and several times throughout your plant’s growth. Calcium and magnesium sulfate are also an excellent additive for tomato plants and can be accomplished by pulverizing eggshells in a blender into a powder (for calcium) and then adding a few tablespoons of Epsom salts (magnesium sulfate) with that and mixing a ½ cup or so of that into the hole at planting time.  

#8 – Harvest Tomato Fruit Slightly Under-ripe

At harvest time pick your fruit just ‘slightly’ under-ripe and bring indoors to ripen. This will prevent the great tragedy of letting your fruit get ‘too ripe’ (i.e. rot) on the vine before you realize it is there, and it will help finish the ripening in a more moderated environment. This is also a great way to get a lot more ripe fruit at the end of the season because even green fruit, just blushing with a bit of color, will ripen indoors quite nicely. Often extending your tomato bounty for weeks beyond what the plants were ripening outside!  

  And now that your patience has paid off…enjoy!

Gorgeous bounty of tomato fruit in various stages of ripening

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