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Hard Frosts Don’t Harm Bulbs

This frost-coated crocus will be totally unharmed.

There has been an early spring in many areas, with the result that bulbous plants are popping up extra early. Some of them may just be showing leaves, but the earliest ones – snowdrops, crocuses, winter aconites, etc. – may well be in bloom. Of course, in some climates, even tulip season has begun. It all depends on where you live.

However, anywhere you can grow hardy bulbs outdoors, there is always a risk of a late frost, even snow. And those risks are increased when spring is earlier than usual. What should you do if a hard frost is predicted and your poor bulbs are already up and growing?

What to Do?

Snowdrops (Galanthus spp.) actually last longer when nights are frosty.

The answer is… nothing. Hardy bulbs (tulips, hyacinths, narcissus, crocuses, etc.) all hail from cold climates, mostly mountainous areas, where irregular spring temperatures are the norm. They’ve had thousands of years of getting used to unseasonable weather. Most will sail right through late frost and even snow without any damage whatsoever, even when they are in full bloom. In fact, frosty nights actually help extend their bloom. I’d seen snowdrops last nearly a month on a regime of cold nights and days barely above freezing, yet only a week or so when the spring was exceptionally warm.

The earliest bloomers, from snowdrops right through muscaris, are the most frost resistant: you often seen them covered in frost crystals at dawn and in perfect shape come noon. Or see them get covered in snow and still blooming away when the snow melts, even days later. In Val-d’Or, Quebec, where the ground remains frozen well into May and nightly frosts are common even in June, tulips routinely get frosted, yet show no damage when they thaw out again.

Heavy Snow

Tulips generally sail right through heavy snows with no damage, but very tall varieties might snap off.

Even heavy snow has little effect on most bulbs: they seem designed by Mother Nature to handle it. Most narcissus, for example, are already somewhat bent over. When snow accumulates, they simply bend down further under its weight then rise back up when it melts. I’d be more concerned by heavy snow on double hyacinths and taller double-flowering tulips, the flowers of which have a tendency to snap off when they get too weighty. It their case, it might be wise to insert a few stakes into the garden, higher than the plants, then cover them with a tarp or old blanket just before the storm, thus creating a sort of snow-proof tent.

But of course, that’s only if heavy snow is predicted and only on a few exceptionally weighty flowers. In most cases, you don’t need to do anything to protect bulbs when frosts or snow are likely to occur.

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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