When is it safe to plant annuals and tender vegetables in the ground? After the last frost, of course.

Have you ever heard of phenology? According to Dictionary.com, “Phenology is the study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life.” Through phenology we can predict spring.

The National Phenology Network collects data nationwide, 24/7, 365 days a year. Among the data collected for plants are the leaf bud, leaf break, bloom time and leaf fall. Data for insects and animals include feeding habits, mating, nesting and hibernating. Professionals and volunteers across the country log these observations into a vast database. The data is graphed along with the weather and seasonal changes and then compared from year to year. Through phenology we see signs that spring is coming, i.e., goldfinch wings turning yellow, lilacs blooming, etc.

Like Punxsutawney Phil, phenology can’t precisely pinpoint the day it’s safe to plant your annuals or seedlings without the fear of frost. However, it can bring to light nature’s signs that spring is near.

Have you heard the frogs peeping? Did you notice the pin oak dropped all its leaves? Are the goldfinches back to their bright yellow selves? These are all nature’s signs that winter is losing its grip, and the spring and summer seasons are just around the bend.

Phenology is also helping track our global weather patterns. Did you know the plant hardiness zones have been updated? Southwestern Pennsylvania has been getting a little wetter and a little warmer, too, overall. Don’t plant that tropical palm tree yet, as our area is still considered zone 6, but we are creeping toward the warmer end of zone 6.

So again, when is it safe to plant annuals and tender vegetable plants outside? Watch nature. Listen to the birds. Learn about the nature in your backyard, and you know. Then give it another week or so for the soil to warm up too.

Washington County Penn State Extension Master Gardeners will have a Spring Gardening Seminar on Saturday, March 14, at the Washington County Fairgrounds. For more information, contact Laura Delach lkd10@psu.edu or 724-207-2001.

Marianne Campbell is a Penn State Extension Master Gardener of Washington County. Washington County Penn State Extension Master Gardeners will hold a Spring Gardening Seminar March 14 at the Washington County Fairgrounds. For more information, call Laura at 724-207-2001. Written by Marianne Campbell Penn State Extension Master Gardener of Washington County.

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