New column: Ask a naturalist

View of fall foliage from the top of Kaaterskill Falls (photo by Dion Ogust)

The Hudson Valley enjoys not only unique and widely celebrated natural beauty, but also a rich legacy as a center of environmental education, preservation and activism. From Mohonk to Clearwater, Scenic Hudson to the John Burroughs Natural History Society and beyond, the region is disproportionately loaded with active, influential and historically significant naturalist institutes, educators, trusts and advocacy groups. This provides locals and tourists alike a multidimensional, expert-mediated relationship with nature if they so choose: a learning opportunity for every trail and vista.

Ask a Naturalist, a new Almanac Weekly column orchestrated by John Burdick, aims to capitalize on this unique community resource and engage a variety of local experts in questions of regional interest and significance. For this inaugural edition, experts from the Mohonk Preserve in New Paltz, the Cary Institute of Ecosystem Studies in Millbrook, the John Burroughs Natural History Society in West Park and the Ulster County Cornell Cooperative Extension in Kingston stepped up to field a variety of season- and region-specific questions.


Which kinds of trees make which color leaves?

Change in day length is the most important factor prompting the onset of fall foliage. As the days grow shorter and darkness increases, leaves stop producing chlorophyll, the green pigment that lets plants convert energy from sunlight. This breakdown allows other colors to take center stage: The yellow, orange, red and brown tones that we associate with fall are always present in leaves, but they are masked by an abundance of chlorophyll during summer’s long days.

Different tree species are associated with different colors. Hickory and sycamore leaves are golden-orange. Ash leaves tend to be yellow and purple. Oaks hold onto their leaves the longest and produce russet-brown foliage. Sugar maples take on an orange or red tone. There is evidence that red leaves are more prevalent when days are warm, dry and sunny, and the nights are cool (but not freezing). Red foliage has also been linked to fungus and drought.

During their lifetime, trees respond to a range of environmental influences, from airborne pollutants to insect pests, many of which can influence leaf color. One year might yield more red and another more gold. The Cary Institute is part of a National Phenology Network project exploring how environmental conditions affect the timing of when leaves change color and fall from trees. Careful monitoring can help answer bigger-picture questions, such as impacts of ozone pollution or climate change.

The Hudson Valley’s autumn leaf show is now on display; a walk on the Cary Institute of Ecosystem Studies’ campus is a great way to view autumn’s splendor. Armchair leaf-viewers can log onto our Tree Cam to see real-time aerial views of changing foliage near the main research building. The Cary Institute’s trails and grounds are open to visitors from 8:30 a.m. to 7 p.m. until October 31, when they close for the winter.

Learn more about phenology, including volunteer opportunities tracking nature’s clock, at

– Lori Quillen
Director of Communications
Cary Institute of Ecosystem Studies

(Photo by Julie O’Connor)

Why do we see so many spiderwebs in the fall?

Autumn is a very active and critical time of year for most of our local spider species. Spiders have spent the better part of the summer growing. As young arachnids, they remained inconspicuous to avoid predation (mainly by other spiders), but now, after several sheds, have reached maturity. Adults can move out from the shadows of the vegetation and are able to spin their own webs.

These webs are often constructed daily, and usually near or under the cloak of darkness. Obviously, we all know how they aid in capturing the spider’s prey, but a web can be a good place to pick up a mate, too. Roving males search for females, who are typically the builders and inhabitants of the webs. After mating and depositing of eggs, the adult spider’s life cycle is over, and they will die off about the time of the first “hard” frost.

Another important element not to be overlooked in the detection of spiderwebs during the fall is the weather. We all enjoy the warm, dewy air of late September days, coupled with refreshingly brisk nights. As a result of the often-dramatic change in temperature each morning, droplets of water will have condensed upon concentric designs all about the garden and woods, illuminating the previous night’s work. 

– Mark DeDea
President, John Burroughs
Natural History Society

When were apples first cultivated in the Hudson Valley?

Apples are thought to have originated between the Caspian and the Black Seas, and proof of humans’ enjoyment of apples traces back at least 750,000 years. Early settlers brought apple seeds with them to America. Records indicate that apples were grown in New England as early as 1630 by John Chapman, also known as Johnny Appleseed, along with many other traders. The first apple orchard on the North American continent was planted in Boston by Reverend William Blaxton in 1625. The only apples native to North America are crabapples, which were once called “common apples.”

It is hard to pinpoint exactly when apples were first cultivated, but in 1730, the first apple nursery was opened in Flushing, New York. An 1845 US apples nursery catalogue sold 350 of the “best” cultivars, showing the proliferation of new North American cultivars by the early 19th century. Well-known American apple orchardists include George Washington and Thomas Jefferson. Cornell reports that the 2012 USDA Census revealed that the 16 counties comprising the Eastern New York Commercial Horticulture program had over 12,500 acres devoted to apple production. The lower Hudson Valley region and the Lake Champlain region are two of the largest and most important apple production areas in New York state, which ranks second in the nation for apple production and first in the country for canned apple products, although much of that crop is produced in western New York.

– Dona Crawford
Community Horticulture Program Coordinator, Cornell Cooperative Extension, Ulster County

Can woolly bear caterpillars predict the weather? 

The familiar “wooly bear” caterpillar, frequently seen this time of year as they move across roadways, trails and backyards in search of a protected nook in which to spend the winter, is the larval form of the Isabella tiger moth. The caterpillars are covered with tiny “hairs” that are a rusty red around the middle and black at each end. These hairs are actually an outgrowth of the exoskeleton, called setae.

Folklore tells us that the more black that appears on wooly bears in the autumn, the harsher the upcoming winter will be. In truth, the proportion of red and black setae is a result of how much the caterpillar has found to eat, plus its age. Wooly bears molt several times, and each time they shed their exoskeleton, they become less black and more red.  However, if the wooly bear has a good feeding season, it will grow quickly, and this rapid growth results in more red and less black.  Regardless, the amount of red and black can tell us about the weather in the past, but not the weather in the future.

While the Isabella tiger moth is the most common “wooly bear” in our area, there are a few (actually a few hundred) other species of tiger moth, each of which looks a little different. For example, the yellow bear caterpillar is all red with no black, while the giant leopard moth caterpillar is solid black with no red. None of these species’ caterpillars tells us about the weather past, present or future.

I’m often asked if wooly bears will sting if picked up, since the setae that cover the wooly bear caterpillar look very prickly, and many caterpillars do sting. In fact, these caterpillars do not sting or bite, and should be safe to handle. However, some people have reported skin irritation after handling wooly bears. This doesn’t seem to bother predators, though. I looked through the Mohonk Preserve’s natural history observation database and found an interesting record written by Daniel Smiley, Jr., dated 24 October 1973: “[Fred] Hough reports that he has seen caterpillars being eaten by bluejays and a praying mantis.”  Clearly, if you’re hungry enough, those prickly setae are no deterrent!

– Elizabeth Long
Director of Conservation Science
Mohonk Preserve