With days growing shorter and hints of frost in the air at times, it’s time once again for New Hampshire’s leaves to start changing color and luring tourists.
As you may know, leaves of certain species of deciduous trees – most famously sugar maples – lose their green chlorophyll as fall arrives. This allows pigments and colors that are normally hidden to show up, sometimes with spectacular results.
The perennial desire to know when and where to see such “peak foliage” has led to a proliferation of online maps and guides about this color change and fueled one of New Hampshire’s most important tourism seasons, roughly centered around Columbus Day weekend.
The New Hampshire Division of Travel and Tourism Development projects that more than 3 million out-of-state, overnight visitors will be in New Hampshire year, spending more than $1.5 billion as they seek vibrant forests.
The reality, however, is that changing leaf color depends on many factors and is rarely predictable.
Most important is the weather on the day you’re doing leaf-peeping, since overcast skies will make even the most gorgeous of woodlots look drab.
In general, day-to-day weather is an important factor in determining how much red we see. A succession of warm, sunny days and cool, crisp but not freezing nights means of sugars are produced in the leaf during the way, but veins going into the leaf close in the evening, trapping those sugars and spurring production of pigments known as anthocyanins, which cause reds, purples, and crimson.
The other major pigment type, carotenoids, are always present in leaves. They cause yellow and gold colors, which tend to be relatively constant from year to year.
Other factors also matter, including the amount of moisture in the soil. A dry summer can delay the onset of fall color by a few weeks.
The best advice for leaf-peeping: Head north whenever you can, and avoid the Kancamagus Highway, which turns into a veritable parking lot in autumn.
New Hampshire’s official foliage tracker can be seen online at visitnh.gov/foliage-tracker.
