Tuesday, May 21, 2013

Spring has finally sprung in Chicago! But is it as late as it seems?

Trout lilies, Trillium and Mayapples in the woods at Chicago Botanic Garden

Trout lilies, Trillium and Mayapples
in the woods at Chicago Botanic Garden; 
Photo courtesy of Kay Havens
I had the pleasure of walking through the Mary Mix McDonald Woods at Chicago Botanic Garden this week to enjoy the amazing display of spring wildflowers. This year, it sure felt like spring was a long time coming. Especially compared to last year when it came remarkably early. I wondered how the spring wildflower timing compared to previous several years in the Chicago area. Thanks to Project BudBurst, I’m able to easily look back at my phenological observations and those of others in the region.

For instance, I’ve been tracking when the first Forsythia flower opens at Chicago Botanic Garden since 2007. The earliest bloom was last year on March 15, 2012; the latest first flower was this year on April 20, 2013. However in 2007 and 2008 we also had first flowers in mid-April (4/16/07 and 4/17/08), 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 non-leap and leap years.

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.  For instance, for Forsythia, they record its bloom period as April 25-May 5. So when we look a little further back in time, even this spring which seemed so late, is earlier than it has been in the past.  I took a similar look at several other species, both native and non-native, for which we have both Project BudBurst data and data from Swink and Wilhelm’s book. About 70% of the species have earlier flowering dates in the last 6 years compared to those recorded by Swink and Wilhelm. I show some of the species that have advanced their flowering dates in the table below.

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

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 about cherry blossoms in Japan (dating back to 900 AD) and grape harvest dates by wine makers in Switzerland (dating back to 1480 AD). Plants have so much to tell us, if we take the time to listen!

Contributed by Dr. Kay Havens

Saturday, March 9, 2013

Bud burst comes to Project BudBurst

Looking at Stages of Leafing out in Chokecherry

Bud burst stage beginning- you can see green leaves under the bud scales
Winter dormant stage

Sometimes young leaves are reddish

Leaves unrolling, this occurs within a few days of the beginning of budburst

The first leaf stage

Today we are having a snowstorm - blizzard. Here in Colorado this mostly is a welcome thing. Its annoying if you have to drive somewhere, but potentially life giving for our parched ranches, prairies and forests.  We remember all too well the fires last summer which were made possible with record droughts and low snowpack. We even had a fire start in a wet mountain valley in Rocky Mountain National Park in November. It burned most of the winter, since there was so little snow. Bizarre. 

It's been a cool but mostly dry winter and spring so far. This means the soil has stayed pretty cold, so even the winter annuals and early bulbs have been slower than usual to emerge. It has been fun to at least vicariously enjoy spring by reading all the reports coming in to Project BudBurst especially from the South and California. It will be interesting to see how plants respond to the wild weather which has effected so much of the USA this year as spring fully develops.

There is a lot more to look for in the early spring of 2013 since Project BudBurst has now added a new phenophase -- bud burst.  So bud burst finally comes to Project BudBurst. You might ask why, up to now, we have not included the bud burst stage in our protocols. The challenge is that how plants prepare for winter and make buds to protect leaf tissue varies widely - so it's a little difficult to come up with a simple consistent definition of when a plant is in the bud burst stage.  Some buds simply burst open with new leaves, others swell, then change colors then reveal brownish or reddish early leaves which will eventually emerge and turn green.  Some plants do not have any leaf scales at all, like many dogwoods and bitterbrush.  These plants have tiny rolled up leaves that usually turn brown or red in the fall, then turn green and expand into normal looking leaves sometime in the spring. It makes sense that plants have a wide variety of ways to get through the winter - this makes it possible for them to adapt to many different climates and conditions. The definition of bud burst which is being used this year (and should apply pretty easily to most deciduous shrubs and trees) is to note when you can see leaves exposed as the scales of the buds spread apart. As long as you are observing a plant that has scales on its buds this should be pretty easy to see. If the leaves are not green you will have to make sure you are seeing leaves and not just other leaf scales.

Bitterbrush winter leaves. They expand into full size green leaves in spring

The date of bud burst is a really important stage to report to Project BudBurst since scientists can use this to precisely determine the beginning of the growing season for each plant species. The timing of bud burst usually reflects the genetics and climate around the tree quite precisely so it is an important way to see how plants are responding to changes in climate or growing conditions. For many trees it is usually easier to see leaf bud burst than first flowers since you can see it on the easy to reach lower branches.

Here in the high plains the first plants to burst their buds are trees that are pollinated by the wind instead of insects. Siberian elm, Green ash, Silver maple, Quaking aspen and Red maple are usually the first ones. Their flower buds are usually quite swollen and rounded just before they burst. They often are reddish or even black in color. The "flowers" are actually just anthers on thin stalks that waver in the wind, spreading pollen far and wide. They may not have any noticeable color at all since there are no petals or sepals. The exception to this general rule is Red maple which can be bright red and can attract insects as well as disperse by wind.

Sibirian elm with male flowers and budburst stage in the leaf bud


Cherry Blossom Blitz

Don't forget about the Cherry Blossom Blitz! Any cherry tree can be used, even the odd ornamental ones. Cherries are already in bloom in the milder parts of the country and should be spreading rapidly north over the next couple of months. There is nothing more spectacular than fruit trees in full flower, turning streets and gardens or even hillsides shades of white or pink. Its a celebrated symbol of the optimism of spring. A great way to help Project BudBurst and enjoy spring at the same time.

Last year we had one of our most successful years with many observations from new observers and new parts of the country.  I am looking forward to seeing what new things will be discovered this year!

Paul Alaback