May Flowers and May Frosts

May Flowers in the Snow

My kids picked these flowers as a Mother’s Day gift for my wife. All the blossoms were collected from the yard around our house. Nice bouquet, eh? There is not much in the vase that a honey bee would find attractive (except for the apple and cherry blossoms) but the kids’ mother really liked the little bouquet. The flowers were picked on Saturday, the day before Mother’s Day. It was 21° C (70° F). Then it snowed. A big heavy snowfall with gigantic flakes. Made me wonder about those flowers still out on the shrubs and trees.

They were OK. It turns out there is a difference between a frost and a freeze. We had a frost. The air temperature, despite the snow and its skiff of accumulation on the ground, stayed above freezing. The ground cooled, of course, but it was breezy and humid so the air temperature stayed mild enough to prevent damaging our future crop of crab apples. It is often like that in this part of the world in the spring. On the other hand, autumns are almost always rather dry here. Many years, the honey season ends abruptly on cold August or September nights when the dry air and lack of cloud cover combine with still calm air. On those sort of nights, the thermometer plunges five or more degrees below freezing. The clover and alfalfa blossoms turn black the next day and the bees are irritable and suddenly without nectar.

There is another dimension to the frost-freeze issue. Weather, as just described, is clearly important (Clear calm nights are bad; breezy cloudy nights are sometimes OK), but obviously the type of flower is important, too. Some plants can produce flowers and keep them blooming even in rather frigid conditions. I assume they are fortified by some sort of natural antifreeze. Flowers such as crocus, willow, skunk cabbage, and asters are quite cold-resistant. On the other hand, many species of plants native to tropical climates are injured in cool weather – even if it stays well above the freezing point. For generations, researchers have tried to breed plants that can survive ambient temperatures cooler than the plant’s comfort zone. But breeding for cold weather tolerance has largely failed.

However, geneticists have recently isolated some of the genes responsible for weathering the cold. In the case of rice, as many as 242 different genes interact to invigorate hardiness in cooler weather. One March, while I traveled in northern Vietnam, in an area near Hanoi, I saw the delayed planting of rice while 1200 kilometres south, near Ho Chi Minh City (Saigon) the first of three sequential harvestings was starting. Stretching the season could feed millions. But modifying even some of the more critical genes out of 242 is a huge challenge. The goal of researching the genetics of frost is motivated by the need to more efficiently feed people. In Vietnam, three crops are grown on each plot in the south; just two in the north. A third crop in the paddies near Hanoi would not require tilling more scarce land; it would require a faster maturing, cold-resistant variety of rice. I would not want delicate begonias blooming in mid-winter in our yard, and would object to research that made such an ugliness of such a beautiful flower possible. We are quite happy with the natural bouquet that our kids picked this spring. On the other hand, if the people with tiny plots of land near Hanoi could each harvest one extra tonne of rice, I would not want to prevent the research that would make it happen.

About Ron Miksha

Ron Miksha is a bee ecologist working at the University of Calgary. He is also a geophysicist and does a bit of science writing and blogging. Ron has worked as a radio broadcaster, a beekeeper, and Earth scientist. (Ask him about seismic waves.) He's based in Calgary, Alberta, Canada.
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