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.