All flowers require sunlight to grow and thrive. While not every flower follows the sun, heliotropic or sun-tracking flowers move throughout the day, absorbing as much light as possible, while phototropic plants grow toward the sun. Some flowers are heliotropic or phototropic throughout their life cycle, while others may mature and stop tracking the sun on its path.
Many sun-tracking or heliotropic flowers grow in harsh climates, including arctic and alpine conditions. In these environments, a short growing season and cool temperatures have led to adaptations that allow plants to thrive. Heliotropic movement enables arctic and alpine flowers, like the snow buttercup and arctic poppy, to absorb as much light and warmth as possible in less than ideal growing conditions. Phototropic flowers grow in a variety of environments.
Photosensitive organs in the plant respond to light, causing a variety of potential responses. Phototropism, seen in sunflowers and other plants, causes the growing parts of the plant to orient toward the sun. Heliotropism is defined by rapid and reversible movement in the plant. The mechanisms that allow the flower to track the sun are located in the upper portion of the stem. According to Candace Galen, professor of biological sciences at the University of Missouri-Columbia, the heliotropic action is similar to that of a seedling seeking sunlight. ProFlowers’ Year of Seeds allows you to start seeds at home and watch this effect for yourself.
Snow buttercups are the most common heliotropic flower. The snow buttercup is bright yellow, with an open bloom. The arctic poppy is a pale yellow blossom covered with fine black hairs. These heliotropic flowers are not typically used for cut flowers and are rarely grown in the home garden, unless you live in their native environment. Phototropic flowers, like sunflowers, are more common in cut flower bouquets, like ProFlowers cheerful Sunshine of My Love Bouquet.
Heliotropism or phototropism enables a plant to absorb more warmth and light. This creates a warm and welcoming environment for insects, increasing the likelihood of pollination. Increased light and warmth may also enable heliotropic flowers to maintain ideal conditions for the production of pollen, improving their reproductive success. Phototropism may enable the plant to grow more seeds, according to Cambridge University Senior Lecturer in Plant Sciences David Henke.
Direct sunlight can impact your cut flower bouquet if it contains phototropic flowers. Place your cut flowers out of direct sunlight to keep your sunflowers or tulips from shifting in their vase, and expect phototropic flowers arranged at a horizontal angle to turn upwards in response to light.