Q&A – When to Change a Fluorescent Tube?

Lynn asks Annie:

Q Hi Annie,

I have a floral cart which uses florescent grow lights. When should I change them? I have had mine on for 2 years set at 8 hours everyday. Some of the tubes are darker at the ends, but none have burned out.

Annie, What do you do? My floral carts are like yours.

A Hi Lynn!

This is a question I’ve answered here before, but it always bears repeating and it’s often asked slightly differently each time.

There are multiple schools of thought on when to change your fluorescent tubes.  In her book, Growing to Show, the late Pauline Bartholomew recommended a schedule for changing tubes during the pre-show schedule for her show plants.

I think that maybe tubes were less expensive back in the day . . . The kind I use (Gro-Lights) are spendy now, and I use them as long as possible; i.e., I generally let my fluorescents go until they burn out.  Mine are on 12 hours/day, except during the pre-show schedule when I begin to expand the time the lights stay on.

When you do change your tubes, remember to change only one at a time on each shelf. The tubes are brighter when they are newer, and I have had plants experience tight centers when they get both tubes changed at the same time. Here are a few old tubes from my stands – hanging out in my garage, waiting to be recycled. The darker ends that you mention are clearly visible. They are usually a precursor to the tubes burning out.

Four burned out fluorescent tubes in Annie's garage
Four burned out fluorescent tubes in Annie’s garage – waiting to be recycled!

I hope this helps!