Of the many signs of spring on Mount Desert Island, the iconic cherry tree (Prunus sargentii x incisa) at Asticou Azalea Garden is a local favorite. People come in droves to photograph it at its peak. It blooms annually, typically in the second full week of May. This season, the flowers did not emerge.
Shockingly bitter temperatures blew into Maine on February 3rd and 4th. At the Asticou Azalea Garden the thermometer recorded 15 degrees Fahrenheit below zero; the windchill was -47 degrees. The cold set records for lowest February temperatures in Maine in over 40 years and came on the heels of a warmer January in which there were several 50-degree days.
In early spring this year, Garden Manager Mary Roper began hearing from colleagues in Connecticut and southern Maine that they were seeing evidence of damaged buds on rhododendrons, including azaleas. Mary began to assess the impact in the garden. A cross section of some buds, like the Rhodora luteum pictured here, showed damage to the developing flowers.
As May arrived, it became clear that the extreme fluctuations in winter temperatures had affected the cherry tree. A close look at the buds showed they were present but unable to open. The tree slowly produced leaves instead of blossoming.
In the 33 years Mary has worked at the garden, she has seen exquisite bloom every year until this one. It is likely that the tree has blossomed every year since 1957, the year Charles Savage planted the “Asticou cherry.”
Dealing with extremes, particularly erratic conditions with shifting temperatures, is difficult for many plants. In cold regions trees and shrubs have a dormancy period in the winter, a strategy to survive while nutrients and water are frozen in the ground. As the weather warms, they emerge from dormancy and begin to grow, at which point low temperatures can cause damage to leaf and flower buds.
When planning and planting gardens, horticulturists consider plant hardiness, the ability to withstand or even require cold temperatures. However, planting zones and hardiness rankings are based on historic weather patterns not the volatile conditions now prevalent with climate change.
Clockwise from top left: Rhododendron 'Waltham' bud showing slight winter impact; Rhododendron luteum bud showing severe damage; Pieris japonica with empty racemes and no flowers at all; Pieris floribunda in full blossom this spring
The effects of the chaotic weather across the Asticou Azalea Garden are varied. Perennial flowers that were below ground when the cold snap hit are blooming as beautifully as ever. Native shrub, Pieris floribunda, had fully blossoming racemes while the Pieris japonica had none. Some azaleas were unaffected, and others lost significant portions of their flowers. The evergreen azaleas seem to be more impacted. Crabapples bloomed, while peaches and cherries were hard hit in this region.
The garden team makes every effort to protect plants from heavy snow, cold, and other winter conditions, including setting up snow and wind screens for more vulnerable plants and propping pine branches to endure heavy snow load. On February 2, as plummeting temperatures were predicted, the care extended to shoveling snow on some plants for better protection.
Preserve staff are working to respond not just to immediate winter conditions but also to climate change. In beds adjacent to the garden, Mary’s team is cultivating plants that are well-adapted for the garden while also mitigating the carbon emissions incurred with shipping plant material.
Severe shifts in weather patterns caused by climate change are affecting anyone who wants to grow something, from farmers and home gardeners to professional horticulturists. Every grower can experiment with strategies to protect plants, as the staff at the Asticou Azalea Garden is doing, but success is not guaranteed.
Keeping our carbon footprints low while adapting to a changing planet may be our best options right now. The Preserve continues to implement practices to reduce carbon emissions in all our operations. When our iconic cherry tree does not flower, it underscores the importance of this work.