This time of the year, I start thinking about my vegetable garden and whether the soil is warm enough to plant some seeds.
Certainly, the weeds have started to sprout and grow.
So let's check with our friends at the AgWeatherNet at Washington State University.
Below is the latest soil temperature at 2 inches down. Lower to mid-50s in western Washington and 50s to lower 60s in eastern Washington. The warmest soil is around Yakima, which is typical.
I sometimes muse about why the Yakima area is so warm. Yakima is in the sinking zone southeast of the Cascades, with the sinking air warming by compression and reducing any clouds. Fewer clouds means more warming solar radiation. You can see the effect today at noon (see visible image below).
The SNAP satellite can measure soil temperature from space....here is a view of the entire West Coast three days ago. Nice and warm soils in California and southern Nevada, with the Yakima to Tri-Cities area the warmest in the NW.
Consider the plot of 2-inch soil temperature at Seattle (near the Urban Horticulture Center at the UW). Soil temperatures had dropped into the 30s back in February during our extended cold period, but it is now just about 50°F. It was around 60°F in mid-October.
Now, back to the big question: what seeds can we plant now?
Considering the following table, there are plenty of vegetable seeds that can be started now, particularly the leafy veggies. But not beans, squash, and melons, which require warm soil.
Time to get working!
Announcement
Grass seed (cool season) needs soil temperatures of 50-65F. According to North Bend Weather (https://www.northbendweather.com/wxsoiltempdetail.php), soil temperatures around North Bend are just poking above 50F. Still too early to put down Tall Fescue grass seed.
ReplyDeleteI’ve equipped my backyard weather station with soil moisture and temperature sensors at 4-6” below ground surface. This year, I’m keeping a log of mean monthly air and soil temperatures for the dual purposes of satisfying my curiosity about the relationship between the two as well as to perhaps add a meaningful layer of depth to my understanding of my microclimate so as to improve my abilities as a gardener.
ReplyDeleteAt my location in Bellingham, the mean monthly air temperature during January was 36.6F and the mean monthly soil temperature was 40.1F, during February the mean monthly air temperature was 37.5F and the mean monthly soil temperature was 38.8F, and during March the mean monthly air temperature was 46.2F and the mean monthly soil temperature was 46.4F.
I essentially avoid growing plants that are potentially susceptible to depredation by the overabundant local wildlife, so the table included in this post isn’t applicable to my situation but it’s interesting to learn about the cultural requirements of other species nonetheless.
As an aside, the only time I’ve observed the ground fully frozen according to all 4 of my soil temperature sensors was during the extreme Whatcom deep freeze of January 2024 which occurred without an insulating blanket of snow cover. The combination of near-0F ambient air temperature along with <-20F wind chill in amazingly deep, bone-dry arctic outflow resulted in the deaths of a number of otherwise very cold-hardy species in my garden!
Has the annual workshop gone inactive? I really enjoyed the two years I attended.
ReplyDeleteRLL... my main partner, the Seattle National Weather Service forecast office, is no longer interested in participating and hosting....need to find another partner..cliff
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