How do bulbs know when to come up? Bulbs, or geophytes to use the botanical term, typically come from regions where plants need strategies to survive difficult climate conditions. And where better to stay relatively safe from freezing cold, heat or hungry herbivores than underground? Growers know that, within certain limits, spring bulbs (and corms and tubers) flower at much the same time every year, suggesting that a sophisticated control mechanism is at work.
Temperature dictates when bulbs emerge from the ground, and many seem to need a cold snap before they begin to grow. The mechanics behind this are not entirely understood, but clearly at some level bulbs have both a “clock”’ and a “thermometer” that tell them when it is safe to start growing.
Spring-flowering bulbs come from regions with very hot summers and cold winters: Mediterranean