How to garden in sync with nature’s calendar in your own backyard

KNOWING YOUR REGION’S first and last frost dates, those seasonal bookends that determine the growing season, is a good start to becoming familiar with local growing conditions. However, frost dates are calculated by compiling and averaging several years of data collected at regional weather stations that often bear little resemblance to a garden — think airport tarmac, not open soil. These days, “average” is an elusive concept.

When climate chaos and calendar collide, look to the natural world for cues as to how the season is progressing. Farmers and gardeners throughout history traditionally have relied on patterns and seasonal rhythms to gauge planting times.

The observation of recurring stages of plant and animal life and their timing relative to weather and climate is called phenology. For example, a caterpillar waits to emerge until the plant on which it feeds leaves out. Likewise, birds delay nesting until nature serves up a caterpillar meal to nurture their young. This elegant system is based on the appearance of a particular plant, which is mostly likely determined by rising soil temperature — that universal gardening bell that rings in the start of every growing season.

Gardeners love to talk about the weather. But there’s weather (what’s happening right now), and then there’s climate (weather conditions over time). In yet another sign that our climate is warming, the USDA bumped up hardiness zones in 2023 for roughly half of the country, including Washington. That’s roughly the equivalent of 5 degrees, which might not seem like much, unless you’re a tender seedling, or a green tomato. Which is to say, these things matter.

Gardeners aren’t wrong to be obsessively attentive to weather conditions. Your garden is like a toad, a coldblooded animal whose metabolism keeps pace with external temperatures.

The short days and cold temperatures of winter bring activity in the garden to a virtual standstill, otherwise known as dormancy. Warming but cool conditions in spring gradually increase the rate of plant growth. The heat of summer initiates peak growth, provided soil fertility and water needs are met. Shorter days and cooling temperatures in fall are the inverse of spring, slowing growth. Weather controls what’s happening in your garden.

Folklore is full of gardening truisms such as, “Plant spinach, lettuce and peas when lilacs show their first leaves.” Keep track of what blooms when; what the weather was doing at that time; and the corresponding appearance, or disappearance, of backyard birds and insects. Over time, you’ll accumulate a picture of the unique seasons found in your own backyard and a series of valuable reminders that when you see this happening in the natural world, it’s time to do that.

I’ll leave you with another piece of age-old wisdom: “If you can sit on the ground with your trousers down, it’s time to plant your seed.” This old potting shed adage is one way to determine when to sow, although most of us prefer the easier and more accurate method of following the instructions on seed packets regarding optimum soil temperatures for germination.

Remember, we’re talking soil temperature, not ambient air temps. An occasional pleasant day is lovely for cooped-up gardeners, but it takes a string of warm weather and lengthening days to raise soil temperature even a few degrees. A soil thermometer is a modest investment and a helpful tool for gardeners looking to keep their pants on.