Abstract
Vascular plants in flower along a fixed 3.8 km route in eight streets in a primarily residential area of urban Cambridge, U.K., were recorded at monthly intervals between January 2016 and December 2019. There was a consistent annual pattern over the four years; the number of flowering species was greatest in June or July but there were still appreciable numbers of species flowering when totals were at their lowest in February or March. Five annuals (Capsella bursa-pastoris, Euphorbia peplus, Poa annua, Senecio vulgaris, Stellaria media) and one perennial (Parietaria judaica) were very frequent and flowered from January to December. Perennial species showed greater variation through the year than annual species. In most months the number of flowering British native species exceeded the combined number of archaeophytes and neophytes, but the native total peaked earlier in the summer and then declined more rapidly than that of the introductions. The transect method appeared to be effective in identifying the main annual phenological trends and also revealed the effects of extreme weather on the patterns in some seasons.
Highlights
In January 2016 I took part in the BSBI New Year Plant Hunt, in which participants were invited to spend up to three hours in the field listing the vascular plants they could find in flower (Marsh, 2016)
The transect study of plant phenology presented here has identified a consistent pattern of broad seasonal trends in the phenology of the urban flora over a period of four years, and in the case of well-studied species these trends are explicable in terms of our knowledge of the reproductive biology of the species
In addition to showing general trends, the results show the influence of climatic extremes in individual seasons and the effects of some major changes in the environment of particular streets
Summary
In January 2016 I took part in the BSBI New Year Plant Hunt, in which participants were invited to spend up to three hours in the field listing the vascular plants they could find in flower (Marsh, 2016). Whatever the time of year, six species, Poa annua, Parietaria judaica, Senecio vulgaris, Stellaria media, Euphorbia peplus and Capsella bursa-pastoris, can be found flowering in most streets (Table 3) They are much the most frequent plants recorded in the study. Its long flowering period has been noted in warmer climates, as in Thessaloniki, Greece (Fotiou et al, 2011) and Sydney, Australia (Bass & Bass, 1990), where it has been studied because of its allergenic pollen In contrast to these species, Erophila verna, Veronica arvensis and V. hederifolia are winter annuals with restricted flowering seasons, a phenology which is largely governed by their germination requirements. A minority of Erigeon canadensis and Mycelis muralis plants can stagger on flowering into the winter and some plants of Polygonum aviculare may even survive in flower through the winter to the early spring
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