Soil Temperature by Month
Asked October 13, 2020, 7:47 AM EDT
For Hillsboro 97124 Trying to Determine appropriate timing for direct sowing flower seeds in the Spring
Washington County Oregon
For tracking soil temperature in the spring for planting, get a soil thermometer.
In general, soil temperature will approach 50 degrees F in early April.
For warm season flowers, the soil temperature will warm to 60 degrees F in mid-May or so.
Here is information about growing plants from seed: https://extension.colostate.edu/topic-areas/yard-garden/growing-plants-from-seed-7-409/
Regardless of soil temperature, you might have mixed results direct seeding flowers. Weeds, birds, and cool/wet soils in the spring make direct seeding challenging. You might have better luck seeding your flower seeds in flats in a controlled environment and then transplanting the seedlings. Here is information about starting seeds indoors: https://extension.umn.edu/planting-and-growing-guides/starting-seeds-indoors