Fairbanks Exhibit: Opening Night

 By Richard B. Primack 

 

“You only need sit still long enough in some attractive spot in the woods that all its inhabitants may exhibit themselves to you by turns.”  Henry David Thoreau in Walden

 

Since 1903, volunteers at the Fairbanks Museum in St. Johnsbury, Vermont have been displaying the first blooms of the local flora on a “Wildflower Table” and recording their observations in logbooks. Volunteers have also been recording the first spring arrival dates of migratory birds. Amanda Gallinat, from Colby College, and I worked with the Museum staff to analyze how these plants and birds are affected by changes in temperature. The Museum recently mounted an exhibit to highlight our findings in a series of posters.  

 

Photo 1: Amanda Gallinat and I meeting with staff behind the Wildflower Table. Note the posters behind us.

 

Amanda Gallinat, several of her students, and I presented our results in a lecture, and met with the public afterwards during a reception.

 

Photo 2: I am presenting an overview of the project to the Museum audience.

 

Our analysis reveals a clear trend in spring-blooming wildflowers: plants are flowering earlier over time, and warmer springs lead to earlier blooming. In contrast, migratory birds are not consistently shifting their migration timing. This means some migratory birds may be out of sync with their food sources.

 

We are grateful for the many decades of committed volunteers and Museum staff who have maintained these records of first blooms and bird migration.

 

Here is a link to the exhibit: LINK

 

Do Plants use the Summer Solstice for Growth Strategies?

 By Richard B. Primack 

 

“Summer passes into autumn in some unimaginable point of time, like the turning of a leaf..” Henry David Thoreau in A Week on the Concord and Merrimack Rivers.

 

A recent high-profile article in the Proceedings of the National Academy of Sciences by Victor Van der Meerschvandermer and E. M. Wolkovich suggests that trees use the time of the summer solstice, the longest day of the year, to determine when to start the process of bud dormancy and leaf senescence that will end the growing season. Trees might even use the summer solstice to gauge how many flower buds will be set for the following year.  

 

Figure 1: The summer solstice is the longest day of the year.

 

I was asked to comment on the article for the Canadian newspaper Globe and Mail, and wrote the following:

 

The study is valuable in showing the potential of the summer solstice in determining major plant process. However, as the authors point out, because the summer solstice also occurs at the time of maximum temperatures, it remains unclear if plants are using day length or temperature to undergo transitions in growth. To disentangle these two factors requires further research with plants in the field and the lab.  

 

Photo 1: Trees may be responsive to the summer solstice.

 

Also, this study considers the general case of all plants, but it is almost certain that different tree species, such as beeches, pines, oaks and maples, will each have their own combinations of environmental cues and ways of responding to future climate change. This question needs to be investigated.

 

And further, we have strong evidence that later in the summer, plants use temperature (both high temperatures and low temperatures), precipitation and soil moisture, and photoperiod to determine the start of bud dormancy and leaf senescence. So perhaps we do not need to hypothesize the addition of another factor, such as summer solstice, especially since it occurs months before the end of the growing season.

 

Photo 2: Is autumn leaf color change triggered by the summer solstice months earlier? 

 

Here is a link to the scientific article: LINK

 

Here are links to two popular articles on this topic: LINK 1 and LINK 2

 

 

Seattle Woody Plants: Trees not Typically Grown in Boston

 By Richard B. Primack 

 

“I suspect that the child plucks its first flower with an insight into its beauty & significance which the subsequent botanist never retains.” Henry David Thoreau in his Journal.

 

 

On a recent spring trip to Seattle, Washington, I encountered many novel woody plants. The wetter and milder climate of the area provides welcoming conditions for many plants which can’t be found, or only found rarely, in Boston.

 

Here are some examples of these trees:

 

Photo 1: Giant redwoods (Sequoiadendron giganteum) are grown as street trees. 

 

Photo 2A: Laurel cherries (Prunus laurocerasus) are commonly grown as hedges. 

 

Photo 2B: Small plants being used to start a hedge.

 

Photo 2C: Open flowers.

 

Photo 3: Chusan palm (Trachycarpus fortunei) growing in a yard.

 

 

 

Seattle Woody Plants: Shrubs and Small Trees

 By Richard B. Primack 

 

“I suspect that the child plucks its first flower with an insight into its beauty & significance which the subsequent botanist never retains.” Henry David Thoreau in his Journal.

 

 

On a recent spring-time trip to Seattle, Washington, I encountered many novel woody plants. The wetter and milder climate of Seattle provides conditions that are amenable to many plants which are not found in Boston, or can only be found there rarely.

 

Photo 1A: Blue blossoms (Ceanothus thyrsiflorus) is a shrub with masses of soft blue flowers.

 

Photo 1B: Close-up of the blue blossoms flowers. 

 

Photo 2A: A variety of flowering dogwood tree (Cornus florida?) that has unusually wide and large bracts.

 

Photo 2B: Close-up of the bracts.

 

Photo 3A: Red claw (Escallonia rubra) is a small shrub with dramatic red flowers. 

 

Photo 3B: Close-up of the Red claw flowers. 

 

Photo 4A: Boxleaf hebe (Hebe buxifolia) is a small shrub with small, symmetrically arranged leaves and an abundance of small white flowers.

 

Photo 4B: Close-up of the Boxleaf hebe flowers. 

 

Photo 5A: Rock rose (Cistus sp.) is a small shrub with large poppy-like flowers.

 

Photo 5B: Close-up of a Rock rose flower. 

 

 

Arnold Arboretum Scenes from May

  By Richard B. Primack 

 

“All nature is doing her best each moment to make us well—she exists for no other end.” Henry David Thoreau in his Journal.

 

Our team is going to the Arnold Arboretum twice a week to make observations of flower visitors for the full range of plants growing at the garden.

 

Photo 1: Ada Fang, Matteo Finnerty, and I making observations on a lilac shrub. 

 

We often notice unusual occurrences as we walk around.

 

Photo 2: A dog walker meet up.

   

Video 1: Snowy clouds of cottonwood seeds blowing through the air. 

 

Our international colleagues are carrying out similar flower visitor surveys at gardens in Korea, India, Scotland, Nova Scotia, Missouri, Hawaii, Czechia, and two places in Germany.   

The Promise of Digital Herbarium Specimens in Large-scale Phenology Research

 By Richard B. Primack 

 

“The book exists for us perchance which will explain our miracles and reveal new ones.” Henry David Thoreau in Walden.

 

The online mobilization of herbaria has made tens of millions of herbarium specimens digitally available. This shift has revolutionized investigations of phenology (the biological study of timing), including plant responses to climate change. 

 

These specimens can be used to demonstrate that plant species are now flowering and leafing out earlier than in the past due to a warming climate.

 

Photo 1: Herbarium specimens, such as this one of a horse chestnut, are increasingly being used in climate change research.

 

Figure 1: Over 100 million digitized herbarium specimens are available online, with about 6 million more specimens being added each year. 

In a recent article published in the New Phytologist, we identify two main themes associated with this growing body of research, and highlight a selection of recent publications investigating phenology at large spatial and temporal scales and in under-studied locations. We also present publications testing long-standing theories and novel questions in ecology and evolution that could not previously be answered. 

 

Photo 2: In one recent study, plum species that flower before they leaf out were shown to live in drier climates than other species. 

 

Photo 3: In another study, male poplar and aspen trees were shown to flower earlier than female trees. These differences might become more pronounced with climate change. 

 

This field will see further breakthroughs as herbaria around the world continue to mobilize and digitally interlink their collections. 

 

Here is a link to the article: LINK

Visiting Scholar in Copenhagen Part 6: Trip to Gothenburg, Sweden

 By Richard B. Primack

 

“Only that traveling is good which reveals to me the value of home and enables me to enjoy it better.” Henry David Thoreau in his Journal.

 

We took a four-day excursion to the University of Gothenburg.

 

Video 1: Crossing the bridge from Copenhagen to Malmo, Sweden. 

 

Photo 1: A huge replica of a flowering tropical tree is suspended at the top of the atrium in the Biology building. 

 

Photo 2: A field trip to the botanical garden to discuss plant ecology and conservation.

 

Photo 3: The central market is still a vibrant food market. 

 

Photo 4: An old photo of the central market as it looked when farmers brought in their produce in horse-drawn wagons. 

 

Photo 5: The interior of the market today. 

 

 

Why are some plants evergreen while others are deciduous?

 By Richard B. Primack

 

"Between every two pines is a doorway to a new world." John Muir.

 

A question that has puzzled generations of scientists and naturalists is, why are some plant species evergreen, while other species are deciduous and drop their leaves in the autumn? In a recent article, I report on the results of a three-year experiment making evergreen white pine saplings drop their leaves each year, effectively making them deciduous. I found that holding onto their leaves for several years helps the pines survive and grow more quickly.

 

Photo 1: At the field site in winter with an abundance of healthy pine saplings.

 

The results of the experiment were strikingly apparent after just one growing season—pine saplings forced to become deciduous grew only 20% as much as the control plants. 

 

Photo 2: A control sapling in winter showing leaves from the previous two years. Two-year-old leaves are present below the 1-year-old lateral shoots. 

 

Photo 3: Sapling in winter with all leaves from previous two years removed. It will make new leaves in the coming spring.

 

An even bigger surprise was in store the following year. By the end of the second year, 75% of the “deciduous” pine saplings had died, in contrast to the evergreen saplings that were all still alive. And by the end of the third year, all the deciduous pine saplings were dead. 

 

This experiment involves a very simple design, going out in the late fall or winter and removing leaves to simulate the life cycle of a deciduous plant species. Despite this simplicity, as far as I know, no one has ever done this type of experiment before.   

 

Publication LINK -- Richard Primack (2025). Later Year Retention of Evergreen Leaves Is Important to Plant Growth and Survival in Eastern White Pine. Northeast Naturalist.

 

 

Flowers and Trees are Blooming Earlier: Is it because of Climate Change?

  By Richard B. Primack 

 

“This world is but a canvas to our imagination.”  Henry David Thoreau in A Week on the Concord and Merrimack Rivers.

 

This week, our research about climate change in Concord combining Thoreau’s records and modern observations was featured the Short Wave program on National Public Radio. This was the first episode of Nature Quest, a monthly Short Wave segment that answers listener questions about their local environment. 

 

Our Concord research highlighted that wildflowers are now blooming earlier and trees are leafing out earlier than in the past, and that these changes are due to a warming climate.  

 

I want to again thank Phil Cafaro, Professor of Environmental Philosophy (recently retired from Colorado State University), for directing us to Thoreau’s records of flowering times. So much of our research over the last 23 years followed from his initial suggestion. 

Here is a link to the story transcript: LINK

Visiting Scholar in Copenhagen Part 5: University of Copenhagen Geology Museum

 By Richard B. Primack

 

“Only that traveling is good which reveals to me the value of home and enables me to enjoy it better.” Henry David Thoreau in his Journal.

 

The University of Copenhagen Geology Museum contains many remarkable historic collections, along with many vibrant new exhibits. The Museum is also grappling with its colonial past, an issue which is linked to many of the collections.

 

Photo 1: This replica of the Ote Worm Museum from the 17^th century represents the origins of the current museum. 

 

Photo 2: The museum has a large collection of polar bears and skulls from Greenland, Denmark’s former colony, which have been used to demonstrate the declining bone mass of polar bears likely due to pesticides and other pollutants.

 

Photo 3: Old seed collections from the colonial past have proved useful for genetic studies; some of the old seeds have even been germinated.

 

Photo 4: The winning photos of the international “Wildlife Photographer of the Year” contest are on display at the museum.  

 

Photo 5: A photograph shows tadpoles migrating in a pond in Canada.

  

Photo 6: A photo of elephants wandering through a village in India.

 

 

 

Visiting Scholar in Copenhagen Part 4: Spring comes to the Botanical Garden

 By Richard B. Primack

 

“Only that traveling is good which reveals to me the value of home and enables me to enjoy it better.” Henry David Thoreau in his Journal.

 

When we arrived in Copenhagen on March 3, the University of Copenhagen Botanical Garden showed only early signs of spring, such as crocuses and snow drops. But by our last day on March 28, many more signs of spring were evident, especially in the rock garden area. 

 

Photo 1: The main rock garden is dotted with color from early spring flowers.

 

Photo 2: Primula vulgaris has one of the most dramatic flower displays.

 

Photo 3: Saxifraga sancta produces a mass of vibrant yellow blossoms.

  

Photo 4: Mukdenia rossii is another saxifrage distinguished by blackened surface rhizomes. 

 

Photo 5: A few early Rhododendrons are putting on a dramatic display of large colorful flowers.