Archives For phenology

Have you ever noticed the first crocuses poking out of the snow or the brilliant, changing colors of fall leaves? If so, we need your help with the critical work of studying how plants are affected by a changing climate.

Budburst, a project adopted by the Chicago Botanic Garden in 2017, brings together citizens, research scientists, educators, and horticulturists to study “phenology,” or the life-cycle events of plants. Wildflower phenology events, for example, are fairly simple: first flower, full flower, first fruit, and full fruiting. Deciduous trees, on the other hand, are more complex, with stages from first buds to leaf drop.

Sweetgum in the summer - Budburst

Sweetgum (Liquidambar styraciflua) seed in the summer.

Sweetgum in the fall - Budburst

Sweetgum (Liquidambar styraciflua) leaves in the fall.

Budburst builds on the basic human drive to notice this kind of changing nature around us and record the information to a database for scientists to review. As director of Budburst, I’m excited to hear about your observations on Fall into Phenology, a study on the autumnal changes you see in plants, or the Nativars Research Project, which looks at how bees, butterflies, and other pollinators react to cultivated varieties of native plants.

Budburst’s Fall into Phenology is not limited to just leaf color and seed; it is about observing plants in the fall. This will be my second autumn with Budburst and the Garden, and I’m looking forward to watching some my favorite plants go through their life-cycle changes. I’ll be keeping an eye on the sweetgum trees (Liquidambar styraciflua) underneath my window at the Regenstein Learning Campus, for instance. I can’t wait to see the beautiful shades of yellow or orange or…well, you just never know.


©2018 Chicago Botanic Garden and my.chicagobotanic.org

This year, it sure felt like spring was a long time coming — especially compared to last year when it seemed that we went straight into summer! I wonder how the wildflower timing of spring compared to previous years in the Chicago area…

Mayapples, April 25, 2012

Mayapples, April 25, 2012

Mayapples, May 2, 2013

Mayapples, May 2, 2013

For several years now, I’ve been working on a web-based citizen scientist project, called Project BudBurst, with colleagues at the National Ecological Observatory Network (NEON). We study the phenology — the timing of natural events like blooming, fruiting, and leaf fall — of plants around the country. Our participants track when plants bloom in their area, and we compare the reports to records from other parts of the country.

You can help us collect data! Sign up to help at Project BudBurst.

For instance, I’ve been tracking when the first forsythia flower opens on the plants near the Garden’s front gate since 2007. The earliest bloom I have on record in that time was last year, on March 15, 2012. The latest first flower for this specimen was this year, on April 20, 2013. In 2007 and 2008, however, we also had first flowers in mid-April (April 16, 2007, and April 17, 2008, respectively). So, as we look back in time, this year’s bloom time doesn’t feel quite so late. In the graph below we show the variation in flowering dates (using Julian dates, which standardize for differences in dates between nonleap and leap years).

forsythia data

In the Chicago area, we have a wealth of phenology data collected by the authors of our local flora, Plants of the Chicago Region by Swink and Wilhelm (1994). While they were gathering data for their book, they recorded when they saw plants in bloom from the late 1950s to the early 1990s. They record the forsythia bloom period as April 25 to May 5. So, when we look still further back in time, our “late” spring is much earlier than it has been in the past.

I took a similar look at several other species, both native and nonnative, for which we have both Project BudBurst data and data from Swink and Wilhelm’s book. About 70 percent of the species have earlier flowering dates in the last six years compared to those recorded by Swink and Wilhelm. Some of the species that have advanced their flowering dates are in the table below.

Species Earliest First Flower Observations
Common name
Genus species
Swink & Wilhelm
1950s – 1990s
Project BudBurst
2007 – 2012
Days
Advanced
Forsythia
Forsythia x intermedia
April 25 March 15 -40
Spiderwort
Tradescantia ohiensis
May 14 April 12 -32
Dogtooth violet
Erythronium americanum
April 6 March 20 -17
Red Maple
Acer rubrum
March 20 March 6 -14
Mayapple
Podophyllum peltatum
May 1 April 17 -13
Lilac
Syringa vulgaris
May 3 March 20 -44
Black locust
Robinia pseudoacacia
May 9 April 20 -19
Bradford pear
Pyrus calleryana
April 15 April 13 -2

Plant phenology, particularly when plants leaf out and bloom in the spring, is remarkably sensitive to the annual weather. Looking at phenological records over much longer periods of time can tell us a lot about how the climate is changing. Many scientists are comparing contemporary bloom times with historic bloom times recorded by naturalists like Aldo Leopold in the early 1900s, and Henry David Thoreau in the mid 1800s, as well as records kept by farmers, gardeners, and others interested in the natural world. Two of the longest phenological data sets are those maintained for cherry blossoms in Japan (dating back to 900 AD) and for grape harvest dates by winemakers in Switzerland (dating back to 1480 AD).

Plants have so much to tell us, if we take the time to listen!


©2013 Chicago Botanic Garden and my.chicagobotanic.org