It is likely you've been keeping the soil too wet.

It there a place on the stem (often it is right at the soil line) that looks a bit pinched and off-color?

If so, damping off is the likely culprit.

Are only the stems limp and the leaves still look fine, or has the foliage wilted as well?

Dawn

Ok, so it appears it is not damping off, which is a good thing. Now, you have to determine what has caused the wilting foliage. When plants are still small seedlings and still confined indoors, there's not too many possibilities to ponder.

Soil that is constantly wet will waterlog the soil and prevent proper uptake of oxygen and nutrients and that can result in wilted foliage. Soil that briefly got too dry could result in wilting, but if that were the case, you probably would have found them limp and wilting in bone-dry soil, not moist. And, if it were an issue of insufficient water, they'd perk up within a few minutes after you watered them, assuming they already hadn't reached the wilt point of no return.

Other than excessively wet or dry soil, the only other possibilities I can think of would be a sudden change in the light level or sudden exposure to strong winds or harsh temperatures. So, has anything changed in terms of lighting, wind or temperature exposure?

And, I am assuming you used a sterile soil-less seed-starting growing medium and sterile flats or containers, which would greatly lessen the likelihood that a plant disease (other than damping off) is in play. I'm also assuming these seedlings or indoors growing under lights, or growing in a properly climate-controlled greenhouse where they haven't been exposed to near-freezing temperatures and where nothing has changed in the last couple of days that could cause wilting.

Finally, have you fed them anything?

Dawn

There was a 24 hour change in lighting- I had to move them to a different room and take away the grow light due to entertaining. This change was yesterday from noon until this morning (when I found them). I did start the seeds in a sterile seed starting flat- these had already been planted up for two weeks in possibly reused potting soil. Everything was healthy and beautiful looking until this morning- I had shown them to my guests yesterday afternoon sometime. Ugh!

Thank you for helping Dawn!!

If they were in significantly weaker light for, let's say, 18 hours, I just don't think that would have caused the wilting but if they were in significantly stronger light, that might have done it. However, for most of the time that they were away from their regular lights, it was nighttime. If they were in a significantly colder or hotter location, that might have played a role. If the amount of wind they're exposed to changed, that could do it. If they were only getting artificial lighting before, and then they had a day of full sun coming through the window and shining directly on them, that could have caused it. If you have a cat who mistook the flat for a litter box, that could have hurt them....though probably not all of them all at once.

Try to look at the wilting foliage as a puzzle we're trying to solve. I'm not comfortable, yet, that we know why they wilted. I want to see what some of the other forum members have to say about this. Maybe they've seen this before with their plants. The only times I've had foliage wilt on plants that are still indoors growing under lights was if I overwatered them or if I have been inattentive and let them get a touch too dry, and then watering perked them right back up.

Have you put them back under the lights? I'd try it and see if they perk up.

If you can, stick your finger down to the bottom of the soil and see if it is dry. Sometimes, with a soil-less growing medium that has peat moss in it, the top can feel damp and the bottom dry or vice versa. It is less of an issue if the growing medium is moist down deeper and dry on top than if it is moist on top and dry down at the bottom. Peat moss tends to hold water a long time, but then when it gets dry, it gets really dry. It can get so dry that it almost refuses to absorb water from a top watering and needs bottom watering instead.

If you have any on hand, liquid seaweed often will perk up a sick plant or plants or, if you have any alfalfa feed pellets handy, soak some in water for a while to make alfalfa tea and then water them with it. Alfalfa contains growth emzymes that sometimes perk up a struggling plant.

Don't give up on them just yet. If the plants haven't been fed since they were planted and they already have 3 sets of true leaves, they may have depleted the nutrition in their growing mix. I do find it telling that the stem remains erect but the leaves are limp. Often that provides a clue that the issue is in the root or vascular system of the plant.

It bothers me a little that they were in reused potting soil. That means that any disease issues existing in that soil may have infected the plants, and that means we could be seeing any one of numerous plant diseases. You can re-use used potting soil, but to be safe you need to put it in the oven and pasteurize it long enough to kill disease microorganisms.

Luckily, if your plants cannot be saved, you have plenty of time to start replacements....but I'm not ready yet to concede that they cannot be saved.

Update:

I placed the tomato plants back under the same conditions before I moved them for company, as stated above, and the oldest leafs are still limp and crinkled up but the stems have actually grown taller!?! I don't know how or why this has happened (I didn't think photosynthesis could happen without leafs?)but they are beginning to sprout new buds! They still are very sickly looking, should I keep hoping they will live to be healthy productive plants or throw them out and start over? The smaller tomato plant that wasn't as large as the others bit the dust- so I will have to start over to replace that one.

There's a certain amount of energy in the cotyledons that sustains the young plants in the first week or so after they sprout and before their leaves begin conducting photosynthesis, so maybe there was enough stored energy to continue growth. Also, if the leaves are not obviously brown, withered and dry, but instead merely limp and still green, they likely are conducting some amount of photosynthesis. I'd leave them alone and let the new buds grow and see how they do. If the plants are strong enough to put out new leaves, they are survivors who deserve a chance to grow and succeed. Larger tomato plants often grow back from the roots from stored energy after they are pounded to the ground by hail or frozen back to the ground. Smaller ones sometimes rebound and sometimes don't.

If you want, you could start a second batch as back-ups. Trust me, with our spring weather and all its erratic behavior, it is always a good idea to have extra plants for back-ups in case your garden gets hit by a very late freeze or snow storm, damaging hail, a downburst, a tornado, strong straight-line winds, wildfire, flooding rains, etc. etc. etc.

I usually pot up about 3 to 4 times as many plants as I intend to plant out into the ground and into containers. When planting time arrives, for each and every plant I put into the ground or into a large container, I put an identical plant of the same variety into a flat labeled "backup plants". Then, if the unthinkable loss of plants occurs, I can replant with exactly the same plants in the same spots. (That means I don't have to relabel stakes with new names and redraw graph paper charts showing what plant is where, which is a huge time saver.)

Even with plants in the ground and backup flats of plants, I have other extras left over that I give away to friends, family members and neighbors---and sometimes even to total strangers who are just driving down the street and stop to look at the garden and say hello.

When we have the annual Spring Fling for members of this forum, I take my back-up flats and the extras with me and give away those plants to whoever wants them. By the time the Spring Fling arrives, which is usually around the last weekend in April, it is getting so late that I'm not likely to need the back-ups, so I want them to go to good homes. It isn't that disaster won't strike after the end of April because May weather can be brutal on tomatoes, but by then, my plants that were transplanted at the right time are strong enough that even if they are mostly destroyed by weather, their root systems are large enough that they generally come back from the roots very quickly.

The worst week for me as a gardener is the week after I've given away every last back-up and extra plant because I've given up the 'security blanket' of having all those extras hanging around just in case they are needed.

I have a question.. I've recently just started planting my tomatoes seeds it was fine and now the stems wilted I put the pots on top of the fridge where it is warm and the soil is still wet.. What am I'm doing wrong..

Bathsheba, You didn't say, but make sure they are not covered and are getting air movement. Damp soil is good, wet soil is not, so make sure you have good drainage. Check the stem close to the soil line and see if it has narrowed. This is damping-off and they will no longer get nutrient to the leaves.

I sometimes sprinkle cinnamon on the top of the soil when planting seeds to prevent damping off. In my house, there is not enough light above the fridge for sprouted tomatoes. They get moved to a sunny window when they sprout.

I HAVE A QUESTION... I STARTED MY GARDEN LIKE 2 WEEKS AGO AND IT SPROUTED WELL.. AND WE SUDDENLY HAD HEAVY RAIN FOR A DAY OR 2 NOW 3 ROWS OF MY GARDEN WILTED DUE TO THE HEAVY RAIN WE HAD.. WILL IT STILL GROW.. I DON'T KNOW WHAT TO DO!!!!! PLEASE HELP. THANK YOU.. AND BY IT'S WILTED SHOULD I JUST LEAVE IT ALONE OR WHAT!!!

What kind of plants? What kind of soil? In other words, is you soil sandy or more clay? Raised bed, in ground or pots? If the soil drains well they may come back. If you find you've planted in a low spot that will remain swampy, probably not. Last year I had large pots planted with tomatoes before the monsoons hit. The soil did not drain as it should and I had to replace them. I never realized there were low spots in my yard till last year when there was standing water for weeks. If I remember correctly, the problem is the saturated soil leaves no room for oxygen, which the roots need to feed the plant. The roots stop growing, the plant droops or drops foliage to try to balance things out. If the soil dries out fast enough, the roots will grow again, but if the soil stays saturated they will eventually die. You really don't want to work in or walk on wet soil. In one raised bed I poked holes with a stick around the tomato roots, hoping the soil would dry faster. (I doubt it did anything, but when you're desperate...).

I'm growing Kale, beets, spinach, tomatoes, bell peppers, and herbs.. it was sprouting real fine and all til we had a heavy rain... I've planted it in the ground in my back yard... and I've also put FAST ACTING LIME INTO THE GROUND BEFORE I PLANTED THE SEEDS.... And it was standing tall as well now i'm worried :'( I've worked so hard Oh and I'm also growing Onions...

As Amy said, if the soil is slow-draining, the plants may be drowning. However, what often follows near-drowing, if the plants survive, is starvation.

In addition to the likelihood that the plants are suffocating/drowing in very wet soil, there is the possibility that the heavy moisture in the soil clogs the plant roots to the point that the plants cannot take up nutrients in the soil. Often, when the plants droop, it initially is because the roots are clogged with water or sitting in tons of water in the soil and cannot breathe and take in oxygen. Then, later on they'll seem to improve and the drooping/wilting will go away, but the plants look discolored and stall and their growth is stunted. These later symptoms relate to the plants' inability to take up nutrients from the soil while their roots are clogged with water.

In both cases, if you planted in grade-level soil, there is not much you can do except wait for it to dry out. If you planted in raised beds, they generally drain better and the plants improve more quickly most of the time.

Are you here in Oklahoma? If so, when did you plant? You listed a lot of cool season plants (kale, beets, spinach....and the onions) and talk about them as if they have only recently sprouted. Kale, beets and spinach should have been planted months ago if you are in zone 7 and slightly later if you are in zone 6, so if you just planted them during the last couple of weeks, you are asking cool-season plants to grow in the warm season, and that tends to not work out too well. That might be a bigger issue for you.

If you are growing bulbing onions and they were planted at the appropriate time for Oklahoma (February 15 - March 10) and if you are in Oklahoma, then your onions should be almost mature by now. They will not necessarily die from excessively moist soil, but it can cause all kinds of problem including diseases that cause mold and/or rot and/or fungal diseases.

Sometimes you see wilting after heavy rainfall and it is not even really related to the rainfall. If you have had a week of cloudy skies and lots of rainfall, then on the first bright, sunny day, the plants may wilt a little bit because of the sunlight---it is just a shock to the plants to suddenly have bright light and heat after a cool, cloudy, rainy week. That sort of wilting usually goes away after a day or two after the plants readjust to that big light shining in the sky.

Thank you so much....with the help