If the color in the pics is accurate and that really is yellow at the base of the leaves (where it joins the stems) - I can't tell for sure from the angle - then it is herbicide damage from drift or from contaminated mulch. Sure seems to be a lot of that going around this year as there have been many similar posts about it on this forum already this spring. Any herbicides sprayed in the area recently? You? Neighbors? County spraying for weeds? If will drift for 1/2 a mile. If it was the mulch then I would have expected it to show up sooner so drift is the most likely cause. Some plants will grow out of it but some won't. If they were mine I would just give them a mild 1/2 strength dose of fertilizer (at the roots only level) and continue to monitor them. Hope this helps. Dave

There is a difference between curling leaves and leaf roll b'c that latter usually appears early in the season and is the result of the root and foliage masses being out of balance, and corrects itelf as the plants mature. Lesuko, Jaune Flammee IS an heirloom tomato variety. My seeds from Norbert in France in 1992. Also, for many years I lived and gardened in Denver so know Boulder well, and the area, at least then and probably still now does not have the more serious viral diseases. What are known as the gemini tomato viruses are found much more often in the South , and now on both coasts, but primarily along the Gulf Coast. I went through the pictures again and I don't see any evidence of 2-4 D herbicide damage, but see below, and if it were I would expect other plants to be affected as well unless they were sheltered from the drift. Stupid Carolyn once Roundupped ( glyphosphate) her tomato field when preparing for a Master Gardeners group that were coming for a visit. Even got up early when no wind was blowing, but never underestimate the drift that can occur. All was well and I damaged just the bottom foliage of a few of the hundreds of plants out there, thank heavens. Lesuko, the only plant I'm not sure about is the third one down, the PL one and it could be 2-4 D damage as was mentioned above, but why just the one plant if it was a drift problem. have you used any herbicides recently or anyone nearby? Or was it a weak spindly seedling when you put it out and it looks young so maybe leaf roll, maybe leaf curl, I don't really know. But again,herbicide damages don't target just one plant, whatever the herbicide is. Carolyn

We need to see a photo of the plant please and many more details about the variety and way it is being grown and your location. From the limited information it could be any number of things including herbicide exposure. Dave

I've see that in my plants and honestly it doesn't cause any problems. If it gets any more extreme, I've had it make the leaves turn into something like balls, just dump the solution and start again. I've tried to re-fresh the solution to get out of it, but it didn't help. If I had to take a guess, I would say too much nitrogen with the main vain of the leaf continuing to grow after the edges have stopped. In looking at your pictures, it looks like you plants might be a little leggy or spindly. I tend to think of them as a teenager, you know growing really fast so they are tall and kind of stretched out. The problem is tomato plants don't back fill. So , you might want to cut back on the nitrogen a little, or increase the sunlight. If you plant gets enough light, it can run with a whole lot of nitro and you will get a thick healthy plant, but the second it gets too much shade, you'll have a plant that is 6-7 feet tall, and the main stalk will be the diameter of a pencil. Totally useless plant that never produces. Good luck.