Early attempts used a High Pressure Sodium bulb that was modified with a little bit of blue light. These "Son Agro" bulbs were manufatured by Phillips. They worked especially well in greenhouses or supplementing Natural Light on Blooming plants. Now , in the 21st century, some Metal Halide Lights have been modified to provide a more complete light for plants. The best of these so far has been the "Clean-Ace" bulb developed in Japan especially for plants. The "Clean-Ace" Metal Halide bulb comes in 250 Watt size and 400 Watt size and will burn in any standard Metal Halide fixture of the same size. It costs more than a standard or Super Metal Halide Bulb, but can be a good compromise for those on a budget.
