DURHAM, N.H.—If past banner leaf peeping seasons are an indication of future years’ color, this year could be a favorable year for New England’s fall foliage season, according to a scientist with the New Hampshire Agricultural Experiment Station at the University of New Hampshire.

According to Heidi Asbjornsen, associate professor of natural resources and the environment, historical trends suggest that, in general, good foliage years occur when springs are fairly mild and wet, sufficient rainfall occurs in the summer, and late summer and early autumn have lots of warm, sunny days and clear, cool nights. New Hampshire has continued to experience unseasonably warm days with abundant sunshine, while nighttime temperatures have overall been above average. The forecast for the New England region calls for a continuation of above-normal temperatures associated with the El Nino that NOAA predicts will strengthen this fall and into the winter of 2018-19, since this would keep the polar jet stream further north than usual.

“This year has been relatively wet, with the exception of periods of moderately dry conditions and periods without substantial rainfall between May and July. Certainly, in August we saw frequent rainstorms and overall wet conditions. We also experienced unusually hot and humid conditions this year, but in general, rainfall and sunshine tend to be more important factors determining fall foliage colors than temperature,” said Asbjornsen. “Leaves also have remained relatively healthy this year, due to a lack of widespread pest or pathogen outbreaks, which would tend to support more favorable fall foliage.”

Asbjornsen is also interested in the possible effects that drought may have on N.H. forests, including potential implications for fall foliage. “There is some evidence from recent studies suggesting that more drought in the autumn can delay peak of redness for some species such as red maple, white oak, while other species may exhibit earlier redness peaks. These include sugar maple, black birch, shagbark hickory, beech, red oak,” said Asbjornsen. “For sugar maple in particular, warmer temperatures during September and October appear to be especially important in producing higher intensity of red leaves. In contrast, more frosts in October tend to reduce red intensities.”   

Going forward, she says the possible effects of climate change – especially increases in the frequency and severity of drought -- on foliage color timing and intensity is especially important for ecotourism, and more research is needed in this area.

This material is based upon work supported by the NH Agricultural Experiment Station, through joint funding of the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 1003450, and the state of New Hampshire. Founded in 1887, the NH Agricultural Experiment Station at the UNH College of Life Sciences and Agriculture is UNH’s original research center and an elemental component of New Hampshire's land-grant university heritage and mission.