Let’s take a little trip back in time…
When I was a kid, I celebrated Thanksgiving with unusual gusto. Part of it was recognizing a few days off from school as a prelude to the long winter break, but the memories I hold most dear include going out into the woods after dinner.
Here I would cross the tree lines separating the farmer’s fields and make my way through the snow.
At last I found myself standing in the middle of a barren field, covered with yellow and gray grass and surrounded by leafless trees. Soon I heard the goofy and somehow soothing sound of Canada geese flying south to warmer climes.
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It used to be a favorite tradition, but nowadays seeing snow on Thanksgiving is a rare occurrence. As a gardener, these climate changes are important to understanding the growing conditions of our yards and our gardens.
change in the garden
Those of you who have been gardening since the 2000s and before have probably noticed a change in growing patterns between then and now.
Annuals that are toasted by September are blooming by November. Just a few weeks ago, I saw apple trees and forsythia blooming in late fall.
Sometimes it’s a scene of joy and excitement, and other times it’s a depressing observation when you’re wondering why your peppers are pushing new flowers the first week of November. If you’ve noticed these changes in yourself, you’re not alone.
Bigger crops are a nice byproduct of warmer temperatures.
A Look at the USDA Growing Zone Map
The United States Department of Agriculture has been a trusted authority for determining which plants can grow in the United States. It relies on decades of records of weather patterns to determine the average highs and lows for a specific area.
Plants such as the desert rose (adenium) will be more likely to bloom without assistance in certain areas.
The USDA Plant Hardiness Zone Map has its origins in the 1960s, when Henry Skinner of the United States National Arboretum produced the first working map of plant hardiness zones. His original vision transformed into the USDA zones we are familiar with today.
In 1990, a growing database of climate records made the first major changes to this map, and in 2012 the map was updated again. We haven’t had an update since then, and we probably shouldn’t expect one for a while.
But how does it work?
The Plant Hardiness Zone Map is separated into regions by average low temperature. Areas range from 1 to 13, with each individual area being divided into an “A” or “B” category.
You can view interactive USDA Growing Zone Maps and also download high resolution versions in a variety of formats.
Each digit between 1 and 13 represents a 10-degree difference in the average low temperature, while an “A” or “B” reduces this temperature difference to a 5-degree increment.
Unpredictable snowfall goes hand in hand with fluctuations in USDA climate zones.
For example, zone 7 has an average temperature of 0 to 10 degrees Fahrenheit; 7a has a minimum of 0 to 5 degrees, and 7b has a minimum of 5 to 10 degrees. Zone 6’s average low is between -10 and 0 degrees Fahrenheit, and zone 8’s average low is between 10 and 20 degrees Fahrenheit.
The climes, they’re a-changin’
Although our planet is certainly warming, this change in USDA plant hardiness measurements between 1990 and 2012 has been officially attributed to more accurate temperature measurements and a system that allows for water, altitude, and other micro-bodies. Takes into account the proximity of the location. climate effect.
It’s getting hot outside!
However, just because 6b was re-labeled as 7a in 2012 in 1990 doesn’t necessarily mean that some plants can now grow in these hot spots. In some regions, these climate changes have been more gradual. In others, you just can’t help but notice them.
According to an article published in November 2019 in the Anchorage Daily News, these changes and their impact on the garden are undeniable. Horticulture columnist Jeff Lowenfels says the Arctic is warming two to three times faster than other places on Earth, and at the time of writing he tracks a 20-month period of record-breaking temperatures. This affects planting time, bloom duration, and everything else, even as gardeners may need to make adjustments to deal with weeds and new invasive plants.
If you started your garden before 2012, subtle changes in climate may explain why harvest times and first and last bloom dates have changed. And even if you’ve been tending to more sensitive plants in your garden during the heat of summer, or hardier plants during the chill of winter, things can change since then.
Sensitive to cold, canna lilies may respond well to warmer climates.
As always, gardeners should take into account the natural habitat of any plant they choose to grow (read more about when full sun doesn’t actually mean full sun, for starters). Some plants thrive in warm climates, but also demand moist and humid environments.
So, the next time you’re shopping for plants and reading the tags like a dutiful gardener, keep in mind that climate, they’re a changer.
Prolonged summers and hot weather can worsen large-scale weather patterns, as the prolonged California drought did in 2016.
To see what hardiness zone you live in, visit the USDA Plant Hardiness Zone Map website and pop in your zip code to find out. Keep in mind that the data you’re viewing was analyzed and documented in 2012, and consult your gardening magazine as a point of comparison so you can adjust accordingly when planning and planting your first vegetable garden.
Hot weather means extra water.
What difference have you noticed in your garden over the years between consistently warm weather, first frosts, or periods of drought or excessive rain? Share in the comments!
Snowy road photo by Matt Suwak, © Ask the Experts, LLC. All rights reserved. See our TOS for more details. Uncredited photos: Shutterstock. Last updated November 22, 2019. With additional writing and editing by Allison Sidhu.