Bulbs come in four forms: ‘true’ bulbs, such as bluebells and snowdrops; corms (eg crocuses); rhizomes (eg wood anemones); and tubers (eg wild carrot).
Bulbs are dormant, underground bunkers of stored energy, nutrients and water. During winter, they remain insulated by the soil, and their roots often continue to grow through the colder months.
Frost initiates a ‘diapause’, causing bulbs to break glucose into smaller molecules and lower their freezing point. Some, such as snowdrops, produce ‘antifreeze’ proteins, preventing ice crystals from forming inside their cells.
Freezing temperatures prompt the chemical reactions in bulbs that then occur once the days begin to lengthen and warm. Then, carbohydrates turn to sugars and the plant ‘breaks dormancy’, pushing out its new shoots.
Milder winters and more erratic earlier or warmer springs, brought on by climate change, can disrupt this ancient process, and prolonged floods can rot bulbs. Their spring flowering is becoming an ever more precious occurrence.
