Leaves are not Growing, but the Stem is

by John
(Glasgow, Scotland)

My seeds are popping and look healthy, but the leaves don't.

Answer: John- the most common problem with young seedlings is over watering. This can cause seedlings to stretch, and can also cause the new leaves to be an unhealthy yellow or pale green color. Without more specific information, this kind of fits your description of the problem. Of course, seedlings will also stretch when the fluorescent light is kept too far away from them (new seedlings can be kept about 3 inches from the bulbs). However, this probably would not account for the lack of leaf growth or unhealthy looking leaves.

If the temperature around your new seedlings drops to 65 degrees F or lower, this could be stressing out your seedlings and stunting the growth of the leaves. Have a thermometer set next to the seed flat and make sure your temperature stays between 68 and 75 degrees both day and night. Low temperature can also encourage wilt and powdery mildew, which could be making your seedlings sick (but which would have probably killed them in just a few days).

New seedlings (first 10 days) should only be fertilized with 1/4 or 1/3 strength nutrient solution. If you have NOT fertilized your new seedlings, the leaves may not be growing due to lack of Nitrogen. If you HAVE fertilized your seedlings, make sure you did not over-fertilize them. Fertilizer should only be applied when the seedlings truly need the water.

Finally, if you have started your seedlings in straight peat moss, the pH of the medium is probably too acidic for the new seedlings. Straight peat moss also retains too much water, making over-watering more of a possible suspect. Next time, mix your peat 50/50 with perilite or vermiculite and make sure it is pH adjusted. Better yet, start your seeds in straight, pre-moistened vermiculite. The mixture is the right moisture when you squeeze a fist full tightly and only get a few drops of water to come out. I hope this helps you out John, and Happy Growing!