Answer: According to cultural instructions to growers from Oglevee's, one of the largest suppliers of geraniums, non-budded Regals (Martha Washington) such as yours would need a four week cooling/bud initiation period when temperatures are kept at or below 56F at night and in the sixties (max 68F) during the day, followed by 8 to 10 weeks of growing on.
According to Penn State, however, while all varieties can be initiated by four weeks at 48 to 50 degrees, some varieties may only require two weeks at that temperature.
Oglevee's indicates that the Regals require an extended day length of 18 hours of light at 10 or more footcandles. In the greenhouse, they suggest using incandescent lighting to provide at least 10 f.c. of light at plant level by stringing 100 w bulbs at 4 foot centers 6 feet above the bench.
According to Penn State, "Regals need mum type lighting from planting until color shows" and Penn State uses 5 watts/sq. ft. of incandescent lighting.
Oglevee's notes that Regals flower better when slightly stressed for moisture starting about 3 to 4 weeks after transplant (although not to the point of wilting -- excess dryness would damage roots and cause leaf scorch)and that when kept too wet or in a high humidity environment, the plants tend to revert to vegetative growth and abort any initiated buds.
Finally, Regals seem to need slighly higher levels of fertilization than typical geraniums, some sources indicating as much as 30% more, so make sure you are fertilizing enough.
You might want to check your foot candle reading and see if you are close to the recommended amount of light. You should also be aware that lower light levels can add about two weeks to the forcing process. I hope this helps you trouble shoot.
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