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How Do Plants and Animals Know It's Spring?

Take a look outside. Birds are chirping, tree leaves are budding, the grass is turning green again. It’s spring! But how do plants and animals know when it’s time to switch from winter to spring? Plants and animals use natural cues to figure out when seasons are changing. It’s all part of nature’s calendar.

(Photo via Shutterstock)

The science of spring

When we look at the changing seasons through the eyes of plants and animals, it is called phenology. Phenology is the study of natural seasons, focusing on plants, animals and the climate. That last part, the climate, is important because it is different in each habitat. Will County has a very different climate than Orange County, California, so our phenology looks different too. Plants and animals who need all four seasons would thrive in Will County, but maybe not in Orange County, where it is warm and dry all the time.

Seeds of change

Tree leaves budding in spring. (Photo via Shutterstock)

Let’s look at plants first, starting with seeds. Around Will County, a lot of seeds drop in the late summer and fall. Before they begin to grow, they need to experience a cold period, like winter. The harsh cold of winter will cause the frozen soil to wear down the coating around the seed, making it easier for it to grow through it in the spring. When the temperature begins to warm in the spring, the plant inside will break through the thinner coating and start growing roots, stems and leaves. The warmed soil is also finally soft enough for them to grow!


Words to know

Cue: An action that serves as a signal for something to happen.

Gene: A unit of heredity that is transferred from parent to offspring.

Phenology: The study of seasonal change in relation to plants, animals and climate.


For plants that are older, they use daylight as their cue. In the winter, we have much less daylight than in the summer. When the days grow longer, many plants begin to grow new leaves or flowers. Most plants have a special gene that tells them when there is the right amount of sunlight for them to grow. It’s different for each plant. When they get that amount of daylight, they can bloom. Virginia bluebells are usually among the first flowers to pop out from the soil and bloom.

Sunshine o’clock

Virginia bluebells at Messenger Woods Nature Preserve. (Photo by Suzy Lyttle)

This may not come as a surprise, but animals use the same cues as plants to switch gears from winter to spring. Animals have more variations in how they deal with winter, like flying south, hibernating or staying active like humans do, but they’re still looking for more sunlight and warmer temperatures to know it’s spring.

Many animals need the plants to grow and bloom before they’ll return or come out of their winter home. Remember those bluebells we talked about before? Because they come out first, a lot of bees and some flies will go to them for pollen or nectar when they first wake up. Hummingbirds, which arrive in Will County in late April or early May, have even been known to use bluebells as their first food source when they come back in the spring.

Seasonal surprises

Plants and animals both use temperature and length of sunlight as cues. Most want warmer temperatures or longer days for growing, getting more active or having babies. Spring is mating season for many of our Will County critters. However, some animals use a totally different timeline. Owls are on a different phenological clock. Their babies are born earlier, at the end of winter, and are already to fly and feast on those just waking up.

Celebrate spring!

Spring has so much to offer in our area. Head out onto the trails or even into your own backyard to see if you can find more signs of spring! Watch the sunset happen later in the evening. Enjoy more sunshine on your face. Wear a rain jacket instead of a winter coat. Use these clues to figure out if spring has really sprung!


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