Friday, May 5, 2006

Bloom Date 2004

Taken from The Peony - C to C
May 2005 Vol 8 Issue 2

by Michael Denny

     It was a very good year for the bloom date project and I want to thank all of those who participated. In 2004, we collected over 1900 observations on the bloom dates of 600 different cultivars.  This brings the overall totals to over 7200 observations on about 950 cultivars.

     Not all of the observations received this year were for observations taken in 2004.  There were several treasure troves of date from earlier years.  The publicity in the APS Bulletin helped to locate several individuals who had been carefully measuring their bloom dates in earlier years.

     It is important to have many observations on each cultivar.  I am pleased that we currently have 10 or more observations on bloom dates for 321 cultivars.  For another 154 cultivars, we have five to nine observations.  The goal is to have 500-600 for which there are ten or more observations.  It should be feasible to reach this goal in the next three years.  There is nothing unique about ten observations.  In my judgement, this amount of data allows us to have considerable confidence in the bloom date.

     There are still many cultivars, 251, with only one observation.  I have kept these in the tables but one should view the data for these cultivars with considerable caution.  As we obtain more observations on these cultivars, the bloom dates may change significantly.  There will always be many cultivars that are not widely grown for which we can not obtain numerous bloom date observations.  However if we keep collecting data we should be able to provide information on all of the widely grown cultivars.

     Mrs. Anne Oveson from Wallowa, Oregon sent me a hand-written list of over 700 bloom date observations.  Mrs. Oveson bred and registered the peonies 'Caroline Rose' and ' Mary Gretchen'.  She collected the data from her own garden and from her sister's garden in Walla Walla, Washington.  The data are from the years 1999 to 2002.  Each sister had from 100 to 150 cultivars and many were common to both gardens.  This provided four to eight new observations on the cultivars that they grew in common.

     Mrs Oveson's data are the main reason why we have twice as many new observations in 2004 than we had last year.  While we can not expect such sources to appear every year, we can continue to add more observations.

     Another historical data set was provided by Bruce Powers of Wisconsin who has data from 1996 - 2004.  To these we can add an unidentified source from Cut Bank, Montana who supplied data from 2001.  These three sources provided one-half of the observations this year.  I am trying to obtain data from another Ohio source who may have data for 50 cultivars from 1993 - 2004.

     The project depends heavily on a core set of Canadian Society contributors.   Val Ames, Brian Porter, Lindsay D'Aoust, Linda Goh and Nick Visser have provided data for three or more years.  Another dozen individuals contributed data for one or two years and we thank them all.  We can always use new contributors.

     As more data are collected there are a number of extensions to the project.  First, we would like to introduce a standard system of describing the bloom period of peonies.  This will avoid the current confusion that arises when different nurseries and different peony books describe the same cultivar inconsistently.  One possibility is to classify peonies by the week in which they bloom with week one being the very early ones and week seven being the latest.

     We know that variations in the weather cause most of the variations in bloom dates at a given location as well as the differences between locations.  We hope to look more formally at this process.

     There is more information about the  project at the we site  The data
 are available and may be downloaded and there are several articles.

     If you want to collect data this year, we welcome your help.  The process is simple.  You should only collect data for cultivars whose identity is known and that are mature plants growing in relatively full sun.  Record the calendar date of the first open bloom.  Keep a list and send them to me at



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