ABSTRACT
The genus Petunia Juss. is a member of the family Solanaceae and consists of over 25 species, most of which are native to South America. Seed catalogs list a bewildering array of petunia cvs, each with varying flower colors, flower densities, and heights. Petunia hybrida is a nonobligate LDP with respect to flowering time. The actual photoperiodic catagory for petunia is somewhat confused. Spector describes petunia as a LDP at high temperature, but DN at low temperatures. When electrical lights were used to increase daylength for petunias, incandescent light resulted in earlier flowering compared with fluorescent light. Petunias require less time to reach anthesis when sowing is delayed from fall until spring, although it is difficult to separate the effect of light intensity from that of increased daylength and temperature. Scheduling of petunias for most rapid flower initiation is very straightforward.
