There is no doubt that climate change has been in the news, particularly in the past decade, and the Western Pennsylvania region has experienced some of those changes. But what are those changes, and how do they affect home gardeners?
“When you put zip codes from Western PA into the USDA growing zone map you notice that many areas have experienced a 3-degree F increase in average winter temperature changes since the last map was published in 2012. These changes reflect changes in averages over the last 30 years,” explained Glen Bupp, Penn State Extension Horticulture Educator. “Because the map is based on 5- degree intervals, this 3-to-4-degree F bump in average temperatures has pushed some areas into a new growing zone.” Noting the Plant Hardiness Zone Chart information is helpful when planning plant selection, planting times and likelihood of pest pressures, according to Bupp.
He continued, “However, it’s better to think of the situation we are in as not simply a warmer climate. Because these are averages, we still get cold spells, but they may not be as prolonged, and the transitional seasons like spring may be more variable. This does not necessarily translate to a new or wider plant palette.”
Randy Soergel, co-owner of Soergel Orchards, agrees with Bupp that while the cold spells may not be as long as prior times, the region is still susceptible, so rethinking all planting patterns may not be the best path. “My perspective is that yes, average temperatures have changed, but you need to determine the temperatures the plants will be able to survive. And you need to know how much are you willing to risk. My suggestion is to just stick to plants that you know are safe in our region.”
Those changes can also bring complications. “Unfortunately, it means that prolonged cold temperatures, which once may have killed off some pest species in an area, may not happen. Plants and insects that break dormancy based on temperatures, or growing degree days, may emerge earlier,” Bupp said.
Rachel Handel, communications director of the Audubon Society of Western Pennsylvania, explained climate changes can have other ramifications. “Climate change has definitely impacted the timing of plants and trees in our area. We’re seeing trees budding and flowering earlier than usual, and we’re also seeing plants emerging earlier than they have in years past. Even small changes can mean big issues for the birds and insects that count on these plants and trees for survival.”
Keeping weather changes in mind, gardeners may want to select plant species with wide-growing zone adaptations. “For instance, if you are in zone 6a, selecting a plant species with a growing zone adaptability of 3-9 means that its likely to be able to handle any weather swings well. Consider avoiding plants that have adapted on the edge of your growing zone. Again, in a 6a zone, it would be unwise to put in a plant with a 3-6 range, or 6b to 8 range,” Bupp explained.
Selecting native plant species is also a safe choice. “These plants have adapted to our area and can generally handle variable growing conditions in our area. Many also happen to have a wide growing zone range and can be found at the north end, southern end, or varying elevation levels across PA. By planting natives, you also help to foster biodiversity and ecological resiliency,” Bupp said.
Handel echoed the native plant suggestion. “It is a great option for gardeners because the plants have evolved to support birds, butterflies, and beneficial insects. These plants produce seeds, berries, and pollen that sustains wildlife during the spring, summer and fall,” she said, “And in the winter, after the plants die back, insects overwinter in the hollow stems. Native plants are adapted to our region’s weather and soil—and can tolerate changes in weather that other plants might not be able to handle.”
Planting dates are also important. “Planting too early may mean risking plants to a late frost. And keep in mind with a frost, typically 32 to 40 degrees, you are usually able to protect plants, but with a freeze, down to 28, it is much harder,” Soergel said. Sticking to the tried-and-true Memorial Day date that our grandparents used to plant their vegetables may not be a bad idea. That doesn’t mean you have to delay all planting, Soergel explained, but purchase plants and keep them indoors until you are sure of the frost-free date. “You can tend to your flats for eight to ten weeks, then plant them outdoors,” he said.
Bupp’s thoughts align with Soergel’s. “Pay close attention to flowering time. If you have an edible landscape, many fruit flowers bloom early and can be negatively impacted by late season frosts. Plants with extended flowering times can help get around this,” he said, “For our pollinators, put in native plants that bloom early. These flowers aren’t always significant in display but can play an unseen role in pollinator health.”
And don’t forget those pests. “Keep an eye out for pests you haven’t seen before. And, have a plan to protect any plants that might have new growth that is sensitive to cold. Cloth is the go-to blanket material for covering plants; don’t use plastic,” Bupp said.
When in doubt, consult an expert. Audubon has a native plant nursery at Beechwood Farms Nature Reserve, where native plants can be purchased along with assistance from experts. Penn State Extension offers various programs and has educators on hand like Bupp to assist as well. And of course, you can visit Soergels. “We have expert staff who will help you plan,” Soergel said.
Bupp offered a simple equation for home gardeners when thinking about how to plant their gardens. “Diversity = resiliency.”
For more information about plant zones:
Information about Penn State Extension classes and experts can be found at: www.extension.psu.edu; 724-602-9965 or email Bupp at: gbb5154@psu.edu.
For information on Audubon including the native plant nursery at Beechwood: www.aswp.org
Soergel’s Orchards: www.soergels.com or 724-935-1743.
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