Phenology

When milkweed begins to bloom is one of the species observed in the Weir Farm NHP phenology program.

NPS Photo

What is phenology?

Phenology is the study of seasonal and life cycle changes for plants and animals. These changes occur throughout the year and can be key indicators of how an ecosystem is affected by shifts in climate and seasons.

These changes are probably already familiar to you—seasonal events like flowers blooming, birds migrating, and leaves turning colors in the fall are all examples of what phenology is studying. Scientists document these routine changes to better understand when different seasonal shifts will occur. These changes can also be compiled together to see the big picture of how seasons and life cycles may be shifting from one year to the next. Data on how species react to climate changes over time informs and improves decisions about how to best protect natural resources. For instance, understanding when invasive species go to seed will help figure out the most effective time to remove them before they continue spreading.

Phenology requires a lot of data to really understand what's going on in the local ecosystems. Without ample data being recorded, the information that is found will not have enough evidence to show what is happening overall. By expanding the number of species being monitored, as well as the number of people who are collecting data, phenology can contribute important and useful information for the future.

Phenology at Weir Farm NHP

Weir Farm National Historical Park has an active phenology program. Volunteers routinely monitor several species and input data online on the National Phenology Network's Nature's Notebook app, which contributes to monitoring and research efforts in the National Park Service. The Weir Farm phenology program currently observes over 30 species of plants, reptiles, amphibians and mammals that are grouped within 8 different mini ecosystems such as upland forest, meadow and pond. The focus of the monitoring is predominately on native plants, many of which are under stress such as the American beech (Fagus grandifolia).

 

On left an herbarium page from Weir Farm's collection, and on right a modern photo of red columbine (Aquilegia canadensis).

Recent research in the Park’s archive has brought to light excerpts of letters that reference phenophases as well as plant specimens that were pressed onsite by Caroline Weir in 1895. These items connect the phenology program to the Weir family’s interactions with landscape in a very meaningful way. Four of the five plants pressed by Caroline appear to still be present on the grounds. In 2025, the phenology volunteers began monitoring a small patch of red columbine (Aquilegia canadensis), which is one of the plants pressed by Caroline over 100 years ago. Efforts are currently underway to begin monitoring 3 of the other species that have been identified with an eye towards evaluating the health of their populations, conservation and restoration.

Letter from Caro Weir in Branchville to Anna Baker in Washington, D.C
“...The violets and apple blossoms are just comming [sic] out and they are so pretty…I will press a violet for you if you would like one…”

 

Get involved!

Interested in contributing to this important citizen science effort? Check out the links below to learn more about volunteering, how to make phenology observations in your own backyard, and how phenology is used throughout the National Park Service.

 

Learn more

• 

  Volunteer at Weir Farm
• 

  Nature's Notebook
• 

  Phenology in the National Park Service