AtD translation: a field of bells emerged into flower

[Mike Jing]

P243.1-6   Across the city noontide a field of bells emerged into flower,
as the boys came swooping in over Murano, above wide-topped red-clay
chimneys the size of smokestacks, known as fumaioli, according to the local
pilot, Zanni. “Very dangerous, the sparks, they could blow up the balloon,
certo,” drops of perspiration flying off his face at all angles, as if
self-propelled.

What does "a field of bells emerged into flower" mean here?