Tomato seedlings yellowing, curling! Help! (Pics included)


Mar 12, 2013
New Jersey
Hey BYC Gardeners,

So I started roughly 70 tomato plants under grow lights in my basement this spring, seeding in mid-late march when I was on spring break, and everything had been going well until about now. Some of my tomato plants have been looking pretty bad recently, and I am not exactly sure why? Some leaves are turning yellow and beginning to curl, and the branches of the seedlings have been starting to droop. I water the tomato seedlings regularly in the morning and then pretty much leave them all day under the light. They get roughly 14 hours of light, which has always been enough. I just plucked one, and the roots did not seem overwatered or rotted, so I am really kind of confused. What is more confusing is that other tomato plants in the bunch are excelling! I have one plant that is almost 6 inches and a deep green color, probably the best tomato I have ever grown (pictured third). I applied fertilizer yesterday at quarter strength (2-5-3 blend of Jobes Organic) and lightly watered the plants to disperse it. What could be the cause of this? Too little water, or too much? Could it be the soil? Any and all suggestions are welcome, as I am really hoping to remedy the issue and have my seedlings thrive. Thanks!

This is a tricky one because this effect can be caused by both over and under watering. More seriously, there is a virus that is carried on aphids and more frequently attacks indoor plants. If i were you I would separate the healthy ones from the yellowing ones and consider whether to destroy them if you are absolutely sure they are neither over or under watered. It won't of course transmit from plant to plant but carefully examine the healthy ones for any sign of aphids.
Luckily, the crisis has been averted. I applied fertilizer and began watering more, HOWEVER, I only water once a day. I believe that sporadic watering throughout the day was too inconsistent and causing some issues with the plants. Seed starting soil also lacks nutrients, so it was pretty much at the point where growing plants needed the fertilizer to continue being healthy. I am worried that the stunted growth due to lack of nutrients may have set them back, as I have many tomato plants that were started in potting soil (nutrients up to 6 months), and they are between 6-8 inches. The largest cherry tomato plant is 4. Looks like I know what mixture to use next year!
It is amazing how quickly plants will respond to nutrients. I would not worry about them being stunted, they are probably only delayed. I have very uneven growth on mine, mainly because the odd one popped up long after the others. It will even itself out though over the next few weeks. Glad you sorted your problem.

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