I started seeds 3 weeks ago in rockwool cubes. After sprouting, I used a weak nutes solution for the seedlings as recommended by the manufacturer (4-6-7 @ 1 tsp./gal. of water), kept seedlings at around 1- 2 inches from floros lamps, 24 hours /day except on sunny days when they were moved to the window sill. I fed and watered the plants by hand, flushing the rockwool with nutes solution at least once per week and watering as needed with just plain water between feedings. At two weeks old and two inches tall, growth began to slow, and the new leaves began to curl downward, although no yellowing occurred. I moved the seedling to four inch rock wool blocks, kept up the same nutes / watering regiment, and moved the seedlings under a 400 watt sodium lamp at a distance of about one and a half feet, 24 hours / day. The problem only worsened. The seedlings, now at three weeks and only 3 inches tall, stopped growing all together, and the new leaves are tiny and curling downwards, but still no yellowing. People have told me the problem must be high nute concentrations, but I disagree for several reasons and have not deviated from the manufacturer??s recommendation. First, the solution I am using is weak, and I only use the nute solution when I noticed the leaf color just start to turn a slightly lime green color signaling the need to replenish the nutes. That happens about once a week. The rich green color quickly returns within the a day or two. Second, nute buildup, is unlikely to occur in just 2 - 3 weeks. When I moved the cubes to 4 inch blocks with no improvement, that pretty much proved conclusively that nute buildup was not the problem. Third, this is my fourth attempt and had the same dismal results.With each attempt, I cut back on the nutes from the manufactures?? recommended dose, as everybody recommended, until I got to their minimum level, the ??lime green color.? And finally, I never saw the usual early warning sign of over fertilizing: the dark forest greening of the leaves which eventually turn almost blueish. Instead, I suspect the problem is too much lighting, since it is the only variable I have not change. I think by keeping the seedlings rather close to the lamps (1" - 2" under floros, 24 hours/day, and full sun when available, or 1- 2 feet under a 400 watt sodium, 24 hours/day is not quite enough to burn them outright, but intense enough to wither them slowly, like what happens with over fertilizing. What do you think?
mahatma Reviewed by mahatma on . Can too much light hurt seedlings? I started seeds 3 weeks ago in rockwool cubes. After sprouting, I used a weak nutes solution for the seedlings as recommended by the manufacturer (4-6-7 @ 1 tsp./gal. of water), kept seedlings at around 1- 2 inches from floros lamps, 24 hours /day except on sunny days when they were moved to the window sill. I fed and watered the plants by hand, flushing the rockwool with nutes solution at least once per week and watering as needed with just plain water between feedings. At two weeks old and Rating: 5