Plants normally and naturally grow in what we call the VEG or GROW cycle, outdoors, until they experience shorter days or less daylight, which occurs naturally around August or September. Then they normally and naturally change to the BLOOM or FLOWER cycle.
There will be no signs of Flowering until that diminished light occurs.
When growing indoors, you change the LIGHT cycle from 24 hours of light (called 24/7) to 12 hours of light and 12 hours of darkenss, called 12/12. AFTER 12/12 begins, within two to three weeks, you then see the SIGNS of flowers.
Plants receive UVA and UVB rays, also called Spectrums, at diferent times of the year.
In spring and early summer, we get the BLUE Spectrum, and in late summer and early autumn, we get the RED Spectrum. Plants need those specific spectrums to flourish and thrive. These rays or spectrums are ,measured in kelvins. So yes, you need a HIGH kelvin bulb like a 6500 K for the VEG Cycle and a low kelvin bulb, like 2700k, for Flowering.