Is spring as late as we think?

Kay Havens —  May 15, 2013 — 2 Comments

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

Kay Havens

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2 responses to Is spring as late as we think?

  1. Interesting info. I checked with some pictures I took of Forsythia intermedia in 1973 & 1974. These were pictures that I had converted from slides. The info on the slide just said late April, no specific date. Those slides I sent to the Garden last year.
    Glenn

  2. Such an interesting post. Thank you! Your historical perspective on bloom times is a great reality check.

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