Hammon Buck has been working with Maine gardeners for more than half a century, and in those five decades he’s seen what a warming trend and climate change are doing to the region’s growing seasons.

“As a child there were a lot of things we could not grow [in Maine] that are now common like Magnolia, weeping cherries and some of the locust trees,” Buck, owner of Plants Unlimited in Rockport, said. “Now those things are quite common with the warming up.”

A noticeable change

Buck is not alone in noticing things are changing in accordance with a continued climate shift.

“A lot of the plant diseases that used to be confined to certain areas of the south are starting to move north,” said Pete Zuck, product manager for vegetables at Johnny’s Selected Seeds. “Viruses that are transported by southern bugs that would be killed off by frost here are gaining ground moving north.”

In recognition of the impact climate change is having on planting, in 2012 the USDA released an updated version of its plant hardiness zone map, which is used by gardeners to determine what flowers, fruits or vegetables grow best in their particular region — or zone.

It’s previous map was released in 1990.

“The planting zones have definitely changed,” Buck said. “We were always a constant zone five but now we are a warmer five with some areas going to zone six.”

What this means to those who plant in Maine, according to climate change experts, is the state’s growing seasons have lengthened, allowing for the introduction of newer crops.

“I think in this is instance climate change is in some ways potentially helpful for the home gardner,” said Dr. John Jemison, professor with University of Maine Cooperative Extension. “That’s a broad brush statement, but a longer season does mean they can grow things they were not able to before and can extend the growing season a bit longer.”

But as helpful as a longer season could be for growing plants and food in Maine, Jemison said it also comes at a cost.

“With this change in climate also comes a lot of other issues,” he said. “There is really no other issue more important to the longevity of humans than climate change.”

According to the University of Maine Climate and Agriculture Network, the average length of Maine’s frost-free growing season is currently 12 to 14 days longer than it was in 1930 and is expected to continue to increase by 2 to 3 days per decade.

Along with this, the minimum winter temperatures in Maine are increasing a rate faster than the daily highs in the other seasons.

With warmer winters, according to the climate network, Maine is also in store for more frequent and intense heat waves during which the feel-like temperature will break 95-degrees.

With the predicted added risk of heatwaves comes more frequent and extreme downpours, according to the agriculture and climate network.

The network’s data shows the frequency of extreme precipitation events in Maine increased 74 percent between 1948 and 2011. Intense storms that used to hit around every 12 months are now occurring every seven months with the maximum hourly rate of precipitation increasing around 35 percent between 2001 and 2013.

The network predicts the frequency and intensity of these extreme weather events will continue over the coming decades bringing risks of increased soil erosion, seed loss, flooding and nutrient runoff.

When it rains, it pours

“One thing that gets to me is this intensity in rainfall,” said Glen Koehler, of the University of Maine Cooperative Extension pest management office. “I started in this 30 years ago and at that time more than an inch of rain in 24 hours we unusual, now — while still not typical — it is happening with more frequency.”

Koehler, who works with Maine’s fruit tree growers, said his farmers have observed the annual rainfall in the state creeping up, but not in a manner beneficial to their crops.

“You see more rain so you think well, no drought,” Koehler said. “But in reality the increased rain is coming in ‘pulses’ and if you go several weeks with no rain, your crops are going to get thirsty and irrigation becomes more important.”

In fact, supplemental watering has become more important at Johnny’s Seeds, according to Zuck.

“We are still seeing Maine get its 45 inches of precipitation a year, but it’s becoming less spread out, more sporadic and in larger amounts when it does rain,” Zuck said. “Here at Johnny’s we never had to irrigate, but the last two drought years did a lot of damage so we have upgraded nad installed irrigation where we never had it in the past.”

As far as home gardening is concerned, Jemison, who has been gardening in Maine for 25 years, said planters need to be prepared for these sporadic rains that he said seem to be creating wetter spring months in Maine.

“Temperatures may be warmer in the spring, but we still seemingly are pushed later for planting because things are so wet,” he said. “One way to deal with that instead of waiting for things to dry out is to make raised garden beds, with good soil drainage.”

Best practices

Climate change, he said, is only going to exacerbate plant diseases and pest issues and he said the best way for the home gardener to battle that is practicing the best gardening possible.

“Having those raised beds really helps dry out the soils,” he said. “That, in turn, helps decrease those diseases and pests that love moist conditions.”

Building organic material into the soil also helps with supplying important nutrients to plants and with proper water drainage, Jemison said.

“I’m a real fan of my raised beds,” he said. “I tend to use bark mulch in the pathways between the beds to help with drainage and slow erosion [and] use black plastic to help warm the soil.”

Jemison also suggests creating methods to capture and store rainwater for use during dry periods.

Gardeners may be tempted to start planting as soon as the weather seems warmer, but Jemison cautions against going all in with what seems to be early springs.

“You may see a lot of early warm weather and ‘mama nature’ says ‘I want to start to leaf out and flower,’ and then she gets hit with a late frost or unexpected cold snap,” he said. “I tell people if they really want to put things in the ground early to start, think twice [because] we are still at risk for the cold snaps.”

If someone is determined to get that early outside planting start, Jemison recommends planting things that are easily and inexpensively re-planted like greens, instead of more costly things like fruit trees.

Trust what has worked

When it comes to what to plant, Buck, whose business celebrates its 40th anniversary this year, recommends sticking with what has worked in the psat, despite what zone changes may have occurred in Maine, or at least doing some homework before planting.

“Warming conditions do offer up some new plants we can grow,” he said. “But don’t bite on every new seed that comes along [and] understand if you are going to experiment with zones, you are taking a risk.”

The key, he said, is to find out if the seed has been thoroughly tested.

“I’ve seen a lot of plants and seeds that are supposed to be hardy for a specific zone, but are not,” Buck said. “If you live in a zone 5, plant for a zone 5 [and] if you want to dabble in zone 6, go for it, but understand the risks.”

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Julia Bayly

Julia Bayly

Julia Bayly is a reporter at the Bangor Daily News with a regular bi-weekly column. Julia has been a freelance travel writer/photographer since 2000.