Weed calendars were kept for January-May 1954 and 1955, involving 75 species, more than half native. Details are given for the 25 most abundant. Percentage of those initiating flowering reached a peak in April; of those actually in bloom, about mid-May. A list and tables are given for the commonest species by month, growth habit, and habitat, with tables of temperatures and precipitation for the two seasons. A study of the phenology of the weeds of Norman was initiated in January of 1954. The purposes of the investigation were to prepare a phenological calendar for the spring weeds and to determine the effects of weather on the phenology of these weeds. In practice field trips were made at least twice a week except during extended periods of cold or rainy weather. On each trip observations were made on foliation, exsertion of flower buds, flowering, fruiting and seed dissemination. From these data, graphic tables and phenological calendars were prepared. RESULTS During the two years of investigation, some phenological data were obtained on 75 herbaceous weeds in Norman. Some species that were present in 1954 were not found in 1955. On the other hand, eight new species were discovered in 1955. In analyzing the detailed record, for 1954 and 1955, it was observed that adequate records were obtained only on the more common species. In view of these facts, data are presented only on the 25 most abundant species. On the species in Table 1, the dandelion, Taraxacum officinale, flowered discontinuously throughout the year, even in December and January. The first plant to initiate anthesis in the spring, therefore, was the shepherd's purse, Capsella Bursa-pastoris. Relatively few new species started to flower in February or March, most of the species initiated flowering in April and a few new ones began to flower in May (Table 1). The flowering period of spring weeds was found to be comparatively long. Many of the earliest flowering species had anthoperiods of twelve or more weeks. Because of this, the peak of flowering of weedy species occurs about May 15. This contrasts markedly with shrubs and trees which reach their flowering maxima about May 1 and April 15 respectively (Table 2). In comparing the phenological weed calendars in 1954 and 1955 it will be observed that no species were in bloom by mid-February, 1954, This content downloaded from 157.55.39.208 on Fri, 14 Oct 2016 04:15:09 UTC All use subject to http://about.jstor.org/terms