How will global warming effect tomato growing in Seattle?
September 7, 2016 2:04 PM   Subscribe

I have a small container garden and I enjoy growing tomatoes. I've had mixed success. Some years, when the summer seems cooler, none of my tomatoes have ripened and I end up throwing out large amounts of rotten vegetables. How will global warming effect the ripening of my tomatoes?

I'm not looking for tips on how to get riper tomatoes. I'm just wondering what will change ten years from now specifically for tomato growing in the eastern Washington area. My reading tells me that tomatoes need a specific temperature range and if it's too hot, they won't ripen. Seattle tends to have a couple of weeks of temperatures in the low 90s every summer - will this temperature peak be longer? Hotter? Will average summer temperatures be higher? Will I finally be able to grow beefsteak tomatoes instead of cherry tomatoes?
posted by bq to Home & Garden (11 answers total)
In ten years, perhaps look into varieties of tomatoes that tolerate a hotter and drier summer:

Climate Impacts in the Northwest

Over the last century, the average annual temperature in the Northwest has risen by about 1.3°F.[2] Temperatures are projected to increase by approximately 3°F to 10°F by the end of the century, with the largest increases expected in the summer.[2] Precipitation in the region has seen a decline in both the amount of total snowfall and the proportion of precipitation falling as snow. Declines in snowpack and streamflows have been observed in the Cascades in recent decades. In Washington state, record low snowpack values were measured in April 2015 and in seventy-four percent of long-term monitoring stations.[3] Changes in average annual precipitation in the Northwest are likely to vary over the century. Summer precipitation is projected to decline by as much as 30%, with less frequent but heavier downpours.

On average, Eastern Washington is already drier than the part of the state west of the Cascades, so if that gets worse, you may want to look into drought-tolerant varieties.
posted by a lungful of dragon at 2:43 PM on September 7, 2016

Here is a nice publication from the UW Climate Impacts Group.

It opens with: "Continued increases in average annual and seasonal Pacific Northwest temperatures are projected as a result of global warming, as well as increases in extreme heat. Projected changes in annual precipitation are small, although heavy rainfall events are projected to become more severe. "

It goes on to give more precise projections. Most of this is couched in terms of the period 2041-2070, because that's what the IPCC published on for PNW in 2013.
posted by SaltySalticid at 2:45 PM on September 7, 2016

Not anything to do with the weather but one gardener said to put an old tire around the plant. Kept the roots warm or something.
posted by sammyo at 3:26 PM on September 7, 2016

Your question as phrased is a bit confusing because you start by mentioning Seattle but then you ask about eastern Washington. So, here are the facts as they currently stand for your area. Seattle reaches 90 degrees F on average on only 1 or 2 days per year (not a few weeks). Spokane in the eastern part of the state reaches 90 on about 20 days per year on average. Ten years is too short a time frame to expect the temperature regime to change enough due to global warming to have any meaningful impact on the growth of tomatoes in your area. The bigger factor for what may happen over the next 10 years would be decadal scale changes in global sea surface temperatures such as the Pacific Decadal Oscillation (PDO), which influences how cool or warm the ocean is in the NE Pacific, which in turn controls large scale jet stream configurations and the sensible weather experienced on the ground in the Pacific NW and elsewhere. So, what can/will happen is that changes in the PDO (and a number of other similar oscillations globally) can cause an overall shift to a pattern of more warmer and drier summers with more 90 degree days, or cooler and cloudier summers with no 90 degree days, all the while over a much longer time frame (like 100 years) the climate is warming.
posted by Seymour Zamboni at 3:36 PM on September 7, 2016 [2 favorites]

There are actually people in Seattle now, with current sun and temp levels, who do very well with tomatoes, even big ones. The key is the amount of sunshine your growing spot gets, not the overall amount of sunshine in the area. (Plus LOTS of water, and nitrogen rich soil and dressing and a cage or other structure that keeps the tomatoes off the ground.)

Having said that, I expect less rain and more sun as we see more effects of global warming, in Seattle as well as elsewhere, and assuming we don't get water rationing, tomatoes will likely enjoy that.
posted by bearwife at 3:56 PM on September 7, 2016

This is a difficult question partly because there are so many varieties of tomato and different varieties are bred for different conditions. Some are fat Midwest US varieties, some from sandy North Africa, others hot weather Sicilian bred. They all prefer different climate conditions.
Which variety are you concerned with?

In my Midwestern garden I plant some that do well in heat, some that do well in drought, some that ripen later and some earlier. I never know what the weather will be and each year a different variety is the most successful.

If this is a question about tomatoes and not global warming, you need to grow a different variety than what you have. Try one that ripens quickly, needs less sun, and doesn't mind wet feet. There are hundreds or thousands of seeds you could start for next year.
posted by littlewater at 4:49 PM on September 7, 2016

I mixed up east and west, because that's the kind of person I am.
posted by bq at 5:16 PM on September 7, 2016

none of my tomatoes have ripened and I end up throwing out large amounts of rotten vegetables

As someone who lives somewhere where tomatoes are unlikely to ripen without a greenhouse, I can tell you that you can definitely put your green tomatoes in a cool place inside and they will eventually turn red, if not super sweet, sometimes even months later.
posted by ssg at 6:08 PM on September 7, 2016 [3 favorites]

The thing is there are hundreds of varieties of tomatoes. Your tomatoes are probably not my tomatoes, and if they are one of us should be growing different ones.

If you are growing brandywines global warming probably won't impact you as much as switching to an Alaskan or Russian tomato would. If this is largely rhetorical you'd want a meteorologist answer, but if you want tomatoes, whether it's next year or twenty years from now you, might want Early Girl, Stupice, Matina, or Moskovich. And always Sungold. And skip brandywines and cherokee purple and others that may require 'management'in a cooler area. There are probably better varieties for your area, but the bottom line is that global warming wouldn't help as much as the right variety and pruning to harass into ripening.
posted by A Terrible Llama at 7:07 PM on September 7, 2016

I'm just wondering what will change ten years from now specifically for tomato growing in the eastern Washington area.

Evaluated over a ten year time span in any single location, any local effect due to global warming is going to be completely swamped by normal local variation. So, basically nothing (this is the factual basis for the "look, it's snowing, so global warming? pffft" line of almost-reasoning).

The way to look for global warming signals is in stuff happening more or less often over the last ten years compared to another ten year period fifty years ago.
posted by flabdablet at 2:57 AM on September 8, 2016

Seattle tends to have a couple of weeks of temperatures in the low 90s every summer

How long have you lived in Seattle? I've lived here since 1988 and the last three summers have been exceptionally hot. A few weeks of temps in the 90s is not normal, not even with global warming taken into consideration. Normal is sunny, 80s-ish and no rain from July 15-September 15. Every five years or so we get a rainy summer where it barely hits 70 all year.

In terms of planning for this, I recommend going to a locally owned nursery for starts, like Sky Nursery on Aurora in Shoreline. They only stock plants (and seeds) that do well in western WA and they are very helpful with questions. They sometimes have master gardeners and landscaping professionals there to do free consultations in the spring, provided you bring pictures and/or soil from the bed where you plan to plant. Find local weather blogs to get a sense of what kind of summer we're in for.

TLDR: As a Seattle long-timer, I would take it season to season.
posted by Pearl928 at 10:26 AM on September 8, 2016 [1 favorite]

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