E-mail- Yellow lower leaves

Q. My plants are 30 days old and the lower leaves are starting to yellow. Please help

A. Hi, thanks for your E-mail

There are a couple things that can cause yellowing leaves.  One that I doubt is your problem since your plants are only 30 days old is that when plants start to flower, often the leaves will turn yellow.  The lower leaves will turn yellow as the nutrients in these leaves are used to make flowers. If your plants are flowering, this is normal.

The first thing your problem may be is a lack of light reaching the lower leaves. When leaves do not get enough light, the cells break down and send the chlorophyll (which makes them look green) to the new cells in the upper leaves that are getting the light (at the top of the plant).

To fix this, you can get a brighter light from HTGSupply.com over your plants so the light gets to the lower leaves. If you are using fluorescent lights, switch to a MH or HPS, if you have a MH or HPS, you may want to get a higher wattage to get more light reflected to your grow area. Your second option, something I have done in the past, is mount fluorescent or LED lights horizontally beside the plants a foot or so below the plant tops depending on what type of light penetration you are getting from your over head light.. This side lighting will provide more light to the lower parts of the plants. You should also consider using reflective mylar or white paint to help reflect the light in the grow room.

The second thing that may be your problem is a nitrogen deficiency. Are the leaves at the top of the plant a light green or a dark green? If they are light lime green, I would give your plants more nitrogen. Nitrogen is the first number listed on a fertilizer, so use something like Fox farm grow big  6-4-4 or anything with a high first number. If the leaves are dark green, I think you need more light.

Btw.   If you think the plants are not getting enough light you may want to induce flowering soon, since light is not getting to the lower parts of the plants, you won’t get flowers or fruit on the lower part of the plants so there is no sense growing the plants much bigger, they will just be putting energy into growing tall with thick stems.
Good Growing,
Dr. E.R. Myers