Tracking Seasonal Changes (Phenology)

Springtime in temperate areas brings longer days (more sunshine), warmer temperatures, and rains. These factors, in turn, trigger sap to run, buds to swell and bloom, insects to hatch, and birds to migrate north. The term for observing and tracking these seasonal changes is phenology.

It all starts with the sun. As sunlight increases in the spring, plants break dormancy and start growing. Animals that eat plants soon appear. (In more arid areas, cooling temperatures actually trigger this greening.) Next, predators who feed on animals show up. (As plant begin to bloom, pollinating insects, birds, and other animals hatch, wake up, or return.) As light decreases and temperatures drop in the fall, the reverse happens. Plants adapt by re-seeding themselves or going dormant; some animals hibernate and others migrate.

As students attend to these changes in the schoolyard or larger environment, they become keen observers of the natural world, developing an understanding of natural relationships, recurring patterns, and the energy flow that fuels the cycles of life.

Observe Seasonal Signs
Have students brainstorm signs that spring (or fall) is approaching, and then keep notes on related observations in the schoolyard, woods, or native plant garden. They might choose to focus on certain plants and set up a routine for collecting data on certain occurrences: buds opening, first leaves appearing, fall color changes, and so on. They should also be sure to note climatic factors, such as air and soil temperatures, precipitation, and day length, that coincide with changes in living things. Questions about animal "happenings" should also arise. For instance, When do certain birds return or leave? When the Monarch butterflies return, how big are the leaves of its larval host plant, common milkweed? Does the appearance of bird and insect pollinators coincide with changes in plants?

(Note: It's best to focus on how native plants respond to seasonal climatic changes. When gardeners water and fertilize garden plants, or use species that are not adapted to local conditions, they are less likely to see changes that are purely influenced by season and climate.)

Explore Planting Advice
Since different plants and animals tend to respond to seasonal changes in predictable ways, farmers traditionally took cues from nature to decide when to plant their crops. For example, some early settlers were told by native people in New England to plant corn "when the white oak leaves were the size of a mouse's ear or squirrel's footprint." Fact or fiction? These growers observed, rightly, that when oak leaves were about that size, the soil was warm enough for corn (and other warm-season plants) to germinate. In fact, farmers and gardeners today still use this kind of information.

Challenge students to keep track of seasonal and climatic conditions that coincide with each of the phenological events below (e.g., shadbush flowering), then determine ideal planting conditions (e.g., soil temperatures) for the corresponding garden crops. The class may also want to keep tabs on what's occurring with wild plants when they typically plant other garden crops, and create their own phenology-based planting tips.

• Plant potatoes when the shadbush flowers.
• When elm leaves are the size of a penny, plant kidney beans.
• Plant peas when daffodils begin to bloom.
• Plant corn when oak leaves are the size of a squirrels' ear.
• Plant morning glory seeds in the garden when the maple tree leaves are full size.