By Larry Hodgson
Question: I bought a hardy gerbera called Garvinea from a local big-box store. It bloomed quite nicely all summer, but do I need to do anything to help it through the winter? I live in hardiness zone 5.
Anwer: How one defines hardiness in plants varies according to climate. If you live in Southern California, a Mexican fan palm (Washingtonia robusta, USDA hardiness zone 9) is hardy. It isn’t in North Pole, Alaska.
Usually, in the gardening world, we start to talk about a plant being hardy when it can grow in USDA hardiness zone 6 (minimum temperature -10?C/-23?C).
By that standard, calling a so-called hardy gerbera by that name is a gross exaggeration. It won’t take temperatures below 14?F (-10?C) … and even then, only for short periods. That would be hardiness zone 8. And it will be seriously damaged at that temperature. The coldest it can take without serious damage is 23?F (-5?C), and only if the cold lasted no more than a few hours. That would be zone 9: almost the subtropics.
If You Live in the South
Of course, if you define being hardy as tolerating a small amount of frost, yes, the label “hardy gerbera” would be appropriate. It can take temperatures just a bit below freezing. So, from a Californian or Floridian point of view, yes, you could say the plant is hardy.
For most American and all Canadian gardeners, though, no, it won’t be hardy, unless…
Winter Protection Can Help… A Bit
Unless you protect it, that is. There are many reports of its surviving in zone 7 well mulched and covered with a frost protecting blanket.
In Zone 6 and Colder
It’s not going to be hardy in zone 5 where you live, unless you do something quite elaborate and not very environmentally friendly, like building a greenhouse over the plant and warming the soil with heating cables. In other words, by creating an artificial zone 8 climate in zone 5.
But you can bring it indoors and grow it on a sunny window ledge. Ideally in a cool room, from 50 to 60?F (10 to 15?C), keeping it just barely moist. That ought to get it through winter, then you can replant it outdoors next spring after all danger of frost has passed.
By my definition, and probably by yours, no, the so-called hardy gerbera isn’t hardy. It’s what I’d call a tender perennial: one not tolerant of cold. But it all depends on where you live and garden!
If your local box store (i.e., in hardiness zone 5) is selling this plant as a hardy gerbera, though, they’re ripping their clients off!