It’s Grow Time!

March 18, 2020 9:09pm
Photo via Lisa Fotios

Or is it? For some plants that like a nip in the air, definitely! For frost-tender plants like basil, that’s a hard no. 

For most annual veggies and flowers, it helps to know when our last frost date will be – the exit of freezing temperatures until fall. Tags or seed catalogs regularly reference this date – “plant x weeks before last frost.”  The trouble is, nobody knows the date – until it happens, and it’s different every year.  

Our best guess is the “average last frost date” which will be right about half the time – and wrong half the time. has Green Lake at Zone 9 April 1-10.

Washington State University says 2019’s actual was March 11, and most recent freezing temp in Seattle this year was March 15th at 30 degrees. 

The Elisabeth C. Miller Library, in answering a reader question, said “The last frost date in Seattle can be as early as March 22, but to be on the safe side, April 15-20 would be more definitive.”

The closer you are to Puget Sound or Lake Washington, the better your odds are of squeaking by without a frost after that date. In Green Lake, likewise, our walls, sidewalks and asphalt streets reflect heat, but nothing beats noticing your own yard’s microclimates – which spot do the plants leaf out first or last, or where does the soil take forever to dry out? 

So there you go. We’re all taking our best guesses. You can plant early, but it comes with some risk, especially for heat-lovers like tomato and basil. Generally they’ll catch up if you wait til it’s more dependably toasty.

You can read all the details about what to plant now in our post here: