In the Garden:
These Himalayan blue poppies are rated hardy in USDA Zones 7 and 8, but are thriving in a Zone 4 garden in Quebec.
Can You Trust the Zone Map?
I fell in love with Meconopsis the moment I saw her photo. Who wouldn't love this beauty, with her alluring sky-blue flowers and delicate nodding buds?
Living in northern Vermont, however, I've learned to be cautious about promising my heart to just any old plant. How many times have I been smitten, only to find my new love has an unsuitable hardiness rating? Sadly, Meconopsis, also known as the Himalayan blue poppy, is rated hardy only in USDA Zones 7 and 8. End of story? Not quite.
A few years ago I visited the famous Metis Gardens (Les Jardins de Metis, also called Reford Gardens) on the Gaspe Peninsula in Quebec, and to my amazement there were thousands of blue poppies in full bloom! I learned that this wasn't a fluke -- Metis is famous for its Meconopsis betonicifolia.
How could this be? I live in northern Vermont, on the border of USDA Zone 3 and 4, and we drove several hours northeast to get to Metis Gardens, so I know they are nowhere near USDA Zone 7. My guess is that even with the moderating effects of the St. Lawrence River, Metis is no warmer than USDA Zone 4. So why does Meconopsis not just survive, but actually thrive there?
Limitations of Hardiness Map
Meconopsis offers a perfect opportunity to discuss the limitations of the USDA Hardiness Zone Map. The map divides the country into zones based on one statistic: the average minimum winter temperature. Meconopsis, rated to zones 7 and 8, would then theoretically thrive in places as diverse as Raleigh, North Carolina; San Antonio, Texas; Las Vegas, Nevada; and Seattle, Washington. Of that list, where will Meconopsis grow reasonably well? Only in Seattle.
Meconopsis cares less about the minimum winter temperature than it does about summer heat and lack of moisture. The plant thrives where summers are relatively cool and moist -- places like the Pacific Northwest, for example. And places very much unlike the other cities mentioned. So the hardiness rating of Zones 7 and 8 isn't particularly useful for determining where this plant will grow.
The Map is Just One Tool
The USDA Hardiness Map is just one tool to use to determine whether a plant will thrive in your region. Do some research on the plant to determine its native habitat, which can give clues to its cultural requirements. For example, Meconopsis, the Himalayan blue poppy, true to its name, is native to the mountains of China and Tibet. It's found in moist alpine meadows at altitudes of about 10,000 to 13,000 feet. While there are few, if any, places in the US that mimic that environment, there are regions that provide the cool summer temperatures, filtered shade, and moist, acidic soil Meconopsis enjoys in its native habitat.
There are also other zone maps, including the Sunset Map, most useful to gardeners in the West, and the Heat Zone map, most useful where soaring summer temperatures damage inappropriate plants. Here in the Northeast, to determine whether a plant will thrive in your garden, begin by checking its USDA Zone rating. Then consult with local horticulturists, refer to plant lists at nearby public gardens, or look in regional plant magazines. You can always take a chance on growing a marginally hardy plant, but if you're like me you like to know what your chances are and what degree of protection you'll have to provide.
Unfortunately, even though cold hardiness probably isn't a limiting factor for me, I still doubt that I can get Meconopsis to grow in my yard. Although the plants survive in Quebec, they are protected from November to May by reliable snow cover -- Metis Gardens get an average of 20 feet of snow each winter! While we tend to have lots of snow where I live, it often doesn't arrive until after some very cold temperatures have damaged susceptible plant crowns. Also, I don't have any spots in my yard with the dappled sunlight and consistent moisture the poppy needs. Of course, I could plant some appropriate shade-producing trees, wait ten years for them to reach an adequate size, and give it a go. Meconopsis is so lovely, I might just do that!
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