Q&A – Light: Too Little or Too Much?


Douglas asks Annie:

Q I have a group of plants in an isolation area.  The light is a 2ft 2-tube T12 fluorescent, about 14 inches above the tops of the plants.  Most of the plants are growing flat, but a couple are growing as if reaching for more light or trying to protect the crown from too much light.  I would like to know how to tell the difference before making adjustments.

If both possibilities look the same, I would assume I would try lower light first as to not harm the plant if it is trying to shield the crown, correct?

The plant pictured is:
Fantasy Girl
218 05/10/1952
R. Behnke/H. Cox
Single lavender/blue or purple fantasy.
Serrated girl foliage.

A Douglas – you’ve asked a Schroedinger’s Cat kind of a question  :-D  Is it too much light, or not enough?  I wish I had an easy, definitive answer for you – but it’s nearly impossible to tell which is which by looking.  It could be reaching for the light, or it could be trying to protect itself from too much light.  There is a way to proceed, however!
Since most of your plantlets seem to be doing well in the conditions you describe, it could just be a cranky plant.  We all get one of those from time to time (you’ll recall the plant of Fisherman’s Paradise that used to be in my collection, and you’ll likely remember video of me gently giving some of my plants a light palm push from time to time).  But you do have some options to work with before bestowing the “cranky” moniker  :-)
First:  The description of this plant doesn’t specify any color to the foliage, but it does look a little pale to me – as though it’s not getting enough nitrogen.  However, I think I can see that the newer growth is looking a bit darker, so I think that’s a good indicator that you’ve got a better balance of fertilizer going now than earlier. So, to begin with, I would groom off those leaves around the bottom.  It’s possible that they are keeping the other leaves from laying down flat (much the way a sucker can distort foliage on a more mature plant).
Second:  If that doesn’t work, then I would say that your assumption to try lower light would be the next step.  Here’s a relatively easy thing to try:  The TP Test.  That’s not its official name, I just call it that because it requires some toilet paper or a tissue.  Since this is a small plantlet, a single square of TP should be plenty.  Single ply is the best.  Place the square over the plantlet – just gentle rest it there and observe the plant for a week or so.  If the leaves begin to relax and flatten out, that’s a pretty good indicator that the light levels for this particular plant are too high. The TP cuts the intensity of the light the way a lace curtain does in a south or west window.
Third:  If there was no change in the plantlet using the TP Test, then remove the TP and move the plantlet a little closer to the tubes to get a little more light and see how it does.
I’m hopeful that one of these will be the answer to your question  :-)