A few years ago, we had a visit from gardener and author Willi Galloway (Grow Cook Eat). She shared with us that in the unpredictable spring weather of the Pacific Northwest, the best way to approach spring planting is through noticing soil temperature. While daytime temps vary a lot this type of year, the soil temperature is much more consistent. If you look at the back of your seed envelope, it may tell you the soil germination temperature.
In my experience, the soil temperature here is the average of the nighttime and daytime temperatures. If the weather warms or cools a great deal, it will take several days for the soil temperature to catch up. Today for example, the high temp is expected to be 57 degrees, and tomorrow cool to 47. So take the average of several days. So our average soil temperature for the next week is somewhere in the range of 45 degrees to 50 degrees.
If you plant seeds before the soil has warmed to their germination temp, they simply won’t germinate, and may just rot. To combat this, many gardeners start seeds indoors. Your seed packet will advise if you can start the variety in pots or not. I have started my tomatoes indoors for quite a few years now. I use a heat mat (made for germinating seeds) to bring the temperature up to the 70-80 range that tomatoes need, and I start them in the house rather than the garage (and then move them out to the garage under a grow light). In the house, I don’t have a fancy setup, I just use a desk lamp over the seeds. One of our gardeners, Jan, wrote this article about growing tomatoes a few years ago: https://hcllutheran.wordpress.com/tag/growing-tomatoes/
Right now, gardeners are itching to get out and plant, with the warming weather and less rain we are having. There are a few techniques you can use.
- Warm the soil by placing black plastic over a patch for a few weeks. While we all want to cut down on plastic use, you may have a few black garbage bags at home that you can reuse after they are done with warming duties.
- Use row cover. This is widely available at garden stores and online. It will warm your plants and soil just a few degrees, and also keep out slugs and pests.
- Use starts, but don’t plant too early.
Here is what you can plant from seed now or soon:
Broccoli Rabe (45 degrees)
Leeks (grow from seedlings)
Radish (45 degrees)
Turnip (45 degrees)
Onions and garlic from sets