The Daily Telegraph - Gardening - - New Books -

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

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