Readme.txt for Hodson Spring Phenology Archive

The data in the Hodson Spring Phenology Archive were compiledÊby Professor Alexander C. Hodson (1906-1996). Professor Hodson was a faculty member in the UniversityÕs Department of Entomology from appointment in 1935 through retirement in 1974. During his career, Professor Hodson examined woody plant specimens of different kinds on and near the St. Paul campus of the University of Minnesota to determine when in spring the plants reached a specified stage of bud, leaf or flower development  His records from 1941 through 1991 are an unprecedented sequence of consecutive phonological observations, and they spanned five decades when indications of climate change were becoming evident.

Professor HodsonÕs records were published as a series of 20-, 30-, 40-, and 50-year phenological records in Minnesota Horticulturalist. Observations made in 1991 have been added in the present archive, and several omissions and typographical errors in the published records found by Janet Moe, William Miller and Roger Moon (Entomology) have been corrected in the present archive.

The archive consists of one Excel table that records the dates when specific plant developmental milestones were reached in each year. The first column records year of observation. The remaining pairs of columns record dates and corresponding numbers of days  (No. d) when specific plant development events occurred. By definition, number of days on January 1 is 1, January 2 is 2, etc. Cells with ÒNAÓ are missing records. Abbreviations for the different events are defined in the following data dictionary.

Field           Description of this field
Eld bds open    Elderberry (Sambucus canadensis L) leaf buds open
Sft maple blm   Soft maple (Acer saccharinum L) flower bloom
Elm blm         American elm (Ulmus americana L) bloom
Lilac bds op    White lilac (Syringia vulgaris L) leaf buds open
Appl grn tps    Apple (Malus domestica Borkh.) cv Wealthy buds at green tip stage
Bur oak grn     Bur oak (Quercus macrocarpa Michx.) buds at green tip stage
Elm lf bds      American elm leaf buds open
Aspen lf buds   Aspen (Populus tremuloides) leaf buds open
Eld blm         Elderberry flower bloom
Appl pink       Apple flowers at pink bud stage
Lilac st bl     White lilac starting to bloom
Lilac full bl   White lilac in full bloom
Appl petal fall Apple flower petals falling
Brid wr bl      Bridal wreath (Spiraea prunifolia Sieb. & Zuff.) in bloom