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Why Do Dandelions Often Rebloom in the Fall?

20161009A.jpgQuestion: Why do dandelions often rebloom in the fall?

Answer: Dandelions (Taraxacum officinale) bloom massively between March and mid-June in most parts of the northern hemisphere, covering fields and lawns beautiful bright yellow flowers, but cease flowering during the summer. Then they often bloom again, at least to some degree, in the fall. Why?

Various studies suggest that the bloom of dandelions is mostly influenced by a combination of day length and temperature. Flowering is initiated by days 12 to 13 hours long, but then the buds actually mature and open more or less quickly as temperatures warm up, usually blooming most heavily when the average daily temperature reaches 60˚F (16˚C). That’s why they can start blooming massively as early as March in warmer regions but as late as June in colder ones.

When the days are long in the middle of summer, no flower initiation normally takes place, but in the fall, when the days shorten to between 12 and 13 hours again, they often bloom a second time; that is, if the weather permits. This second flowering either peters out as days shorten further or ceases with the first severe frosts.

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

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