Can the circular florecent bulbs be used as grow lights. i have some 100 watt and a 138 watt day light bulb. what kind of area will they cover and about how high over the plants do i hang them?
Yes they can be used.
100W/138W? Is that 100W/138W equivalent? Each would be good for about a square foot of lit area. You can use them to supplemental natural light from a window, or for low light plants like African Violets, over maybe twice that area.