At the New York Botanical Garden in the Bronx, an experimental plot was in full flower on a recent February afternoon, as the thermometer edged toward 60.

The Japanese camellias, which typically bloom in early spring, have displayed their rose-hued flowers continuously since December. Honeybees, a rarity before late March, were nursing the tiny pink clusters on a Dawn viburnum, while the Adonis amurensis, a ground-hugging spring ephemeral, was a profusion of yellow.

“This is the earliest I’ve seen all of these things in flower,” said Todd Forrest, the garden’s vice president for horticulture and living collections. “The ground isn’t even frozen. That’s shocking.”

The horticulturalists in the Bronx call it the global-warming garden, and in a winter notable for its consistent mildness, it is hardly unusual. From the Shakespeare Garden in Central Park to the Chicago Botanic Garden, flowering bulbs and other plants are bursting out two to four weeks ahead of schedule. Snowdrops are up; daffodils, crocuses and hellebores are already in flower; trailing phlox has opened; and, farther afield, even magnolia trees are starting to bloom on the National Mall in Washington.