40. FLOWERS THAT FOLLOW THE SUN

Heliotropic flowers, such as sunflowers and calendulas, are known for their ability to track the sun as it moves from east to west during the day. Young sunflower (Helianthus annuus) buds and leaves follow the sun then swing back to the east overnight. When the sunflower blossoms, the stem stiffens and it no longer moves. The seed head remains facing east toward the sun as the seeds develop. The common field marigold (Calendula arvensis) of central and southern Europe does the same—it traverses a 19-degree arc from east to west every day, seemingly following the movement of the sun.

Heliotropism of flowers and leaves illustrates how plants have adapted to their environment in ingenious ways. In cold climates, heliotropic flowers that face east in the morning heat up more quickly than west-facing flowers. This added warmth attracts bees and other pollinators which, studies have found, prefer warmer flowers in the morning. This finding confirms the old gardeners’ advice to grow vegetable and flower gardens with a full exposure to eastern sunlight and the morning sun. Plants seem to grow better when they receive early morning light. They warm up faster, the dew dries off quicker, and pollinators visit the warm flowers facing the rising sun before any others.

You can see heliotropism at work with the fragrant annual heliotrope (Heliotropium arborescens), Iceland poppies (Papaver nudicaule), and an alpine plant known as the snow buttercup (Ranunculus adoneus). The yellow-orange blossoms of the California poppy (Eschscholzia californica) also follow the sun. Heliotropism shows us that plants are more active than we think. So grow heliotropic flowers and enjoy the movement.

The bright, yellow-orange blossoms of the California poppy (Eschscholzia californica) follow the sun. They open as the sun’s rays touch the blossoms and close as dusk descends. This annual has flowers atop finely cut silvery green foliage. Blooms over a long period. Drought tolerant. These poppies reseed themselves every year. Hardy in zones 5–10; it’s a perennial in the warmer climates of zones 8–10.