Joined: Mon May 20, 2013 10:42 pm
I think you'll notice a slight difference between the two images, perhaps the size of the plants is slightly different? Believe it or not, the plants in both pots are the same age. They are D. capensis Alba which I germinated from seed on October 8th of last year. I transplanted 7 plants to each pot which are filled with a mixture of 1:1 peat and perlite plus a thin topdressing on chopped sphagnum moss. Since transplanting I have done my best to keep them growing in the same conditions, with the exception of they type of light they receive. One of the pots I placed on a sunny windowsill which receives 5-6 hours of direct sunlight each day and the other I placed in a small aquarium under two 17W 6500K t8 bulbs 24" long on a 12 hour photo period. Does anyone care to guess which pot of plants was under each type of light?
Surprisingly (or not?) the plants grown under artificial light have grown many times faster than those under sunlight. This is by no means a perfect experiment with all but one factor being controlled, however I think this is a good example of how insufficient the sunlight passing through modern double pane windows is. According to an app I downloaded onto my phone which measures lux (not the right metric, ideally we would measure PAR or PUR — photosynthetically active radiation and photosynthetically usable radiation) the sunny windowsill is currently receiving a max of over 120,000 lux while the plants under the fluorescent lighting are only receiving a mere 6,000 lux. This seems counterintuitive that the plants receiving light much more intense have such dramatically lower growth rate. I am not a scientist so I can't give you a good reason exactly why this happens and I am open to suggestions or ideas, but I believe it has to do with how the light gets filtered by the glass.
I'm not writing this to tell anyone not to grow their plants on windowsills as it clearly can be done, just that perhaps it is worth considering investing in a cheap fluorescent fixture or led light to grow plants under. In this phase of the experiment the plants were grown under similar temperatures and humidity but not exactly the same. I want to do another experiment in the future like this which will correct those factors as well as the most blaringly obvious inconsistency here — the photoperiod. Let me know what y'all think about this, any thoughts or recommendations for things I should try out in the future.
My grow list and germination log