Following on from my last post here is another reader question (From James) regarding leggy chilli seedlings and grow lights.
I started some some plants from seed. They took a couple weeks to germinate but they finally came up. the sun is too hot outside for the little seedlings so I put them under a grow light I bought at Home Depot. It is a Phillips incandescent bulb and I put it in a desk lamp and shined it down on the seedlings. About a week or two later the seedling have grown dramatically but they are all stems and have not even begun to show true leaves even though they are 3-4 inches tall. Is this normal?
I have seen pictures of much smaller plants that have at least two sets of true leaves and are have the size. I was thinking maybe the light frequency is wrong and should change lights. What are you thoughts?
There are a couple of points i’d like to discuss that are brought up by your question.
First of all I’ve noticed that different varieties of chillies tend to produce very different shaped plants, even at a very early stage of growth. The picture above is of a Cayenne seedling which always tend to be a bit leggy, no matter how much light they receive. At the other end of the scale varieties such as Naga or Jolokia produce very compact seedlings that focus their early growth on foliage production rather than putting on height. Therefore much will depend on which variety you are growing.
You mention that you are using incandescent bulbs. While they can be used to promote growth in the early stages the big downside of these bulbs is the large amounts of heat they produce. To be very effective they need to be very close to the plants, usually so close that the delicate seedlings end up getting scorched or damaged. By far the best type of lights to use for young chilli plants are Compact Fluorescent Bulbs as they output very little heat.
OK, so if your seedlings are a bit leggy what can you do? Recently I talked about the best ways to pot on chilli plants and mentioned that if plants are slightly leggy you can simply plant them a bit deeper when re-potting them. Doing so will encourage more roots to sprout from the buried part of the stem, making a stronger healthier plant in the long term.