Friday, October 07, 2011

Only half of my fall mum bloomed? What gives?

Fall is the perfect season for gardeners to finally be able to chop down their poorly placed annuals. But also, it can be a grand time to catch some mistakes.

Last fall, we planted some garden mums in our front flower bed for late season color. They looked grand. After they finally succumbed to late fall freezes. I simply cut them back thinking that they surely won't survive our winter. But one did.

Share photos on twitter with Twitpic So this lone garden chrysanthemum grew well in the flower bed enjoying its southern exposure with filtered shade from my crabapple and plenty of water. I anxiously waited for it to bloom. But wait! Did it mutate over the summer?

Why is only half of the plant in bloom? This is just crazy, or is it?

So what is the issue. Some of you are saying, "C'mon Steve, you're such a dummy, you have landscape lights in front of the plant and that is throwing off the photoperiod. Photoperiod? Ray Kessler at Auburn University explains this well on his Chrysanthemum web page.
The chrysanthemum is a qualitative short-day plant with respect to flowering with temperature modifying the photoperiodic response. Plants flower when the day-length is shorter than the critical day-length and grow vegetatively when the day-length is longer than the critical day-length. However, chrysanthemums have two critical photoperiods, one for floral initiation and a different one for flower development. However, there is no single critical photoperiod because it can vary depending on the cultivar and temperature.
Look closely and you will see that there are landscape lamps on both sides of the plant. These are very inexpensive solar LED landscape lamps and their light quality is very much to the blue spectrum. So this can not be the problem. Photoperiodsm is controlled by red and far-red light, the other end of the spectrum from these LED's output. BUT, what you can not see in the photograph is that there are lights on the front of my garage, which we leave on at night for some security and those bulbs are 100 watt incandescent bulbs. The garage lights are the culprit. Incandescent bulbs generate a lot of red light, which is causing the light polution that is slowing down the bloom on the right side of this plant.

Will it ever bloom? Eventually, but probably not before first frost, which may come this weekend.


George Elliott said...

i am so going to cop this photo for my photoperiod lecture...

Steve Newman said...

George, do you need a better picture?