2018 spring bloom markers

I was hoping to simplify my tracking of spring bloom markers, but instead I added another marker, Growing Degree Days (GDD), which is easy to calculate using free web-based tools.  Julian Day allows me to convert MM-DD-YYYY date format which spans 3 months (February to April) into a seamless day of the year format. GDD is a major convenience, I can tap into a database of daily temperature minimum and maximum instead of recording my own observations.  Focusing on the last two graph points, the accumulated warming this year is roughly 25 days delayed compared to last year (84 versus 59).

Here I compare additional observations with GDD, 1) Acer leaf-out in my backyard and 2) first day that the pollen count exceeds 1000.  Notice how well these markers follow similar graph trends.

Here I show a free web-based tool by AgroClimate which compares this year's GDD to the previous year.  Reading from left-to-right, notice where the curves depart - last year's accumulated warming began in mid January, approximately 30 days earlier than this year.  If the daily high does not exceed 50°F, then the daily contribution to accumulated GDD is zero - the curve does not grow in height. I love this graph layout, but I can't use this tool to go back further in history. This tool can draw the average GDD (not shown), but we all know that no such thing exists in the wild - we have never experienced an average year of weather.

Here I show a free web-based tool by Weather Underground which I used to calculate GDD beyond the previous year in history.  In previous years, I kept the starting point equal to January 1, and I change the ending point in a trial and error manner to achieve a GDD value close to 296.  Why 296 - this is the GDD value where the Atlanta pollen count exceeds 1000 this year.

                     2009 2010 2011 2016 2017 2018 

                      day  day  day  day  day  day

Bradford Pear          65   79   60        56   53
Carpenter Bees         68   87   72        63   77
Acer palmatum leaf out 73   92   77        64   76
Carolina Cherry Laurel 73   97   83        57   76
Pollen Count over 1000                76   51   84
GDD=296 (base 50°F)    92  104   93   84   59   84
Here I show other values that do not appear in the graphs.

2017 spring markers & honey cap

What feels odd about the first photo?  Maybe it's the expectation that the flowers are larger than bees - not in this case of this holly bush. Here's another prolific flowering tree in the neighborhood - Carolina Cherry Laurel appears in the second photo.

                     2009 2010 2011 2016 2017
                      day  day  day  day  day
Bradford Pear          65   79   60        56
Carpenter Bees         68   87   72        63
Acer palmatum leaf out 73   92   77        64
Carolina Cherry Laurel 73   97   83        57
Pollen Count over 1000                76   51

The point of tracking these day-of-year values is to synchronize my beekeeping practices with spring weather.  The first step/acknowledgement is to admit that there is no such thing as an average year- we have never experienced an average year of weather.  My journal contains spring marker dates which sometimes appear in different months.  So, dates are converted to day-of-year to make the comparison between years easier.  I'm experimenting with comparing first pollen count over 1000.  Pollen count is easy to acquire, loosely correlates with temperature and maybe more objective than my journal notes.

I first saw Steve Page speak at Georgia Beekeepers Association in 2015 on the topic of Sustainable Beekeeping.   Do you want to learn more, sign-up for "It's Time To..." the free email mentoring of Coweta Sustainable Beekeeping.  As Steve is influenced by other beekeepers - so, I'm influenced by Steve and have adapted my beekeeping management which uses Kelly foundationless (F Style) frames.  Last Monday (day 65), I removed the bee cozy and checker-boarded the honey cap of my hives.  

off with the bee cozy & spring markers 2012

Bee foraging on redbud tree

Bee foraging on burford holly bush


We returned from a two week UK trip to discover all of my spring markers present (today is day 71 of this year).   Our winter was exceptionally warm and compared to the past three years, the spring markers have come early. 

                              2009               2010                 2011

                         Day of Year        Day of Year          Day of Year

Bradford Pear               65                 79                   60

Carpenter Bees              68                 87                   72

Acer palmatum leaf out      73                 92                   77

Flowering Dogwood           80                 93                   80

Asian Wisteria              83                 96                   81

Carolina Cherry Laurel      73                 97                   83

I removed the bee cozys and during the inspection discover tons of bees and brood in all of the boxes.  I can't say enough good things about the bee cozy--at $15, the reusable bee cozy is a no-brainer.  Despite redbud tree and burford holly bush forage, the bees are more defensive than I expected, perhaps this is consistent with the absence of  a major nectar flow.  Did I nearly miss all of the Atlanta spring?--all except the tulip poplar flow.

bloom calendar / spring markers

                                    2009               2010              2011
                              Day of Year    Day of Year    Day of Year
Bradford Pear                 65                 79                   60
Carpenter Bees              68                 87                   72
Acer palmatum leaf out  73                 92                   77
Flowering Dogwood       80                 93                   80
Asian Wisteria                83                 96                   81
Carolina Cherry Laurel   73                 97                   83

In Atlanta, the arrival of the 2011 spring markers are remarkably similar to 2009.   So, as not to color my 2011 observations, I have intentionally not reviewed my old journal notes......too much.  Picking "the date" for these spring markers requires more patience and discipline than I am always prepared to apply.  Naturally, I want to escape winter and embrace spring.....ticking-off the entire spring marker list during one warm day.   My journal contains spring marker dates which sometimes appear in different months.  So, the dates are converted to day-of-year to make the comparison between years easier.

I speculate that this year, enthusiastic yard clean-up has made it less obvious to spot the arrival of the invasive Asian Wisteria bloom near "my local" coffee shop. My wood deck is a dependable habitat for those territorial wood nibblers (a.k.a. carpenter bees) who emerge/return to same piece of lumber each year.  For example, the carpenter bee arrival are observations only recorded in my backyard....another self imposed rule to my scheme.

cold duration

I tapped into the climate records from the University of Georgia cold duration calculator.  So, it's not just my imagination, but this past winter has been a particularly prolonged cold winter.  This winter our purple heart plant died, but this plant survived the past 5 winters outdoors.

Has prolonged cold temperatures altered when trees bloom or the arrival of other spring markers? My backyard record keeping could be better, but it looks like a ~19 day delay of spring markers when comparing 2010 with 2009.

Bradford Pear              20-MAR-2010    15-FEB-2009    33 day delay 

Carpenter Bees             28-MAR-2010    09-MAR-2009    19 day delay

Acer palmatum leaf out     02-APR-2010    14-MAR-2009    19 day delay

Flowering Dogwood          03-APR-2010    21-MAR-2009    13 day delay

Asian Wisteria             06-APR-2010    24-MAR-2009    13 day delay

Carolina Cherry Laurel     07-APR-2010    14-MAR-2009    24 day delay