TC Reader Question: Tomato Seedlings and Light
Tomato Casual reader Justin writes:
“I have about 15 big beef tomato plants in that have been growing since February under 2 48′ 40watts and 2 48′ 25watts florescent. I live in Ohio.
The ones under the 25watt have stems twice to three times as thick, extremely uniformly dark green leaves, tons more canopy, tons more hairs and stickyness on the stems, and a little more purple under the leaves.
The ones under the other light are lighter green, small stems, but no purple under the leaves and seem healthier?? They almost seem like different strains but are the same seeds from burpee.com. Do the dark ones have a disease??”
Hello Justin. What an intriguing problem! Thick stems and dark green leaves are actually signs of very healthy tomato plants. It is possible that they are somehow a different variety, though this is not likely.
Are the lights on each set of plants at the same height? Seedlings do well with the lights 2-3″ above your trays. As they grow, move the lights up to be 6″ above your growing plants.
Seedling plants need fluorescent lights that provide from 15-20 watts per square foot. Your 25watt bulbs are providing 12 watts per foot (since you have 2 lights). The 40 watt setup is providing 20 watts per foot. Your 25 watt setup is slightly low, but this would have produced weaker, lighter green plants, not darker ones, if they were truly having problems.
The purple leaves are something to watch, as this is one sign of phosphorous deficiency. Has it been coiler in your house lately? Your soil may be fine, but colder temperatures can inhibit the ability of your plants to use the phosphorous that is there. Too much water or too little can also affect the phosphorous intake. You may want to test the soil to see if the levels of phosphorous are adequate.
I think you should be fine with both plants. Remember to harden them off before placing them outside, so they can get used to natural sunlight. Good luck!
May 1st, 2009 at 8:02 am
Dear Justin,
I could help you in solving your “light” problem but to reach this goal you should tell me wich Burpee’s variety you are growing: I will check my opinion in Burpee website and only after that I will can give a right explanation.
As far as concern the purple colour, most probably it is due to cold temperature.
Bye.
May 1st, 2009 at 2:25 pm
I’ll be as interested in an answer as you!