How Often Should I Replace My Grow-Light Bulbs?

Dear Dan,
We have a garden that we have done a few harvests in already. Suddenly, it seems that it is taking longer than 8 weeks for the buds to be ripe. I was wondering if the light we are using in the flower room is getting older would cause the growth rate to slow down? — Onstar in Lake Tahoe

Dear Onstar,

If the strain you’re growing now is the same one you grew in the past, then it’s likely that your bulb needs replacing. HID (High Intensity Discharge) grow bulbs such as HPS (High-Pressure Sodium and MH (Metal Halide) need to be replaced approximately every year in order to perform at optimum levels. Even more often, if they run 24 hours per day and not on the 12/12 on/off lighting cycle. Worn out bulbs will still send out light but at diminished levels, and replacement bulbs are fairly affordable, making it a no-brainer to replace the bulbs for more light and bigger yields quicker.