Tomato seedlings wonky


That is plenty of hours, actually overkill. The plants do not look leggy to me from your pics. Another thing to look at are the roots if at this stage of growth they should be nice and white, if they they are brownish then your over watering is taking a toll. Roots need oxygen as much as water and to much water depletes the soil of oxygen. Pull out your worst looking seedling and let us know.


I thought he said at the lights, with the soil being closer to 60. The soil needs to be warm for tomatoes.


I dug and replanted a few deeper and the roots look good. Soil temp when the lights are on is in the 70s. I stuck a low-reading digital meat thermometer in there.


I have a max/Min thermometer that sits at plant level. Highest temp 91, lowest 63.


It’s not that they’re leggy. None of them grow straight up, they all grow at an angle.


Personally, if those were my seedlings all I would do is back off on watering. They look good to me. If all you are doing is growing seedlings for planting out in your garden you are in good shape at this point.


ok. I’ll do that.


I would include a fan to strengthen up the stems. Moving air will also help eliminate any soil born pathogens. A rotating fan that stands up a couple feet away should do the trick. They’ll straighten up over time, sometimes they get bent emerging from the soil and sometimes they lean towards the light, which is why it’s a good idea to rotate them around every once in a while.

They look pretty good to me.


This is not directed toward O.P. This is a general tomato growing suggestion re growing seedlings. Tomatoes are upland tropical adapted plants. They do not tolerate excess watering. Seedlings grow best if watered well, then let dry to the point of wilting. There is a reason for doing this. Tomato plants “imprint” the conditions they grow in. If grown with restricted water, their root system expands until it is significantly larger than seedlings that have never been water stressed. This pattern of growing a large root system continues when the seedling is transplanted. Having a larger root system is one of the keys to producing huge crops of tomatoes.

The only other trick I’ve found worth using is to expose seedlings to two separate nights of temperatures between 40 and 45 degrees. A study - which can be found online - showed that plants exposed to cold temperatures produce fruit earlier and produce more total fruit. I leave the heat off in the greenhouse for a couple of early spring nights when the temperature is in this range.

Tomatoes go through a juvenile stage which is entirely composed of expanding the plant and producing a larger root system, stem, and leaf surface. At a genetically determined point, the plant will set a cluster of flowers. The flowers trigger hormonal changes in the plant that cause it to stop expanding so fast and focus on maturing fruit. Keep a plant in the juvenile stage as long as possible to produce larger crops.

In the adult phase, a tomato plant produces flower clusters and sets fruit. There is a point where the plant has a few fruit the size of a quarter that is critical to have an abundance of nutrients in the soil. This is the time to apply a bit of extra fertilizer. I give my plants a shovel full of dried chicken manure at this stage.


Current temp at plant level.


Great info Darrel, well put.


Hi Bryan, I think your tomatoes are doing fine. They seem pretty young yet. Some varieties just grow like that till they’re older. Maybe just give them some time. Possibly they might be reacting a bit to too long or too close lights? And possibly heavy soil. When I’ve had seedlings look somewhat like yours (leaves not spreading out) I think it was due to too heavy soil. The next year I added more sharp sand to my mix (I make my own) and that helped. But every year is different and different tomatoes grow differently so it’s hard to say. As others have mentioned, when you transplant maybe consider adding some vermiculite/perlite/sharp sand type stuff to the mix? Or try some other mix?

My plants often get watered from the top even when started in pots, just because it’s easier and I have a lot of plants. When they’re transplanted it’s into flats in the greenhouse and there they always get watered from the top. And it isn’t very warm especially in their early days (45-70) so they’re always on the purple side. They get more light as the days get longer.

I don’t let them dry out completely, just the top of the soil before watering. They’re in natural light maybe 12 hrs, though on cloudy overcast days I supplement with LED lights (now that I have them - never did before and I still had good plants). And I have strong healthy plants by the time it’s ready to transplant outside. I think they’re pretty hardy souls, and seem fairly forgiving. I grow all early maturing varieties. Maybe longer season types need warmer temps? But it sounds like yours are plenty warm.

My greenhouse, by nature of walking in and out and vents, has a pretty good amount of air circulation but it also has a couple of small fans when the temp gets into the 60’s and I think that helps a lot for healthy plants. Don’t know if that might be something you could add (or need).

Hopefully your plants will grow up and strong the way you want them to as they mature. Sue


I agree - it’s the purple tinge that’s worrisome

Mine went purple last year as seedlings and never did do really well


After another full day. Highest temp was 100, lowest 57.

Maybe too big of a temp swing? I’m not sure how to remedy that.


When light is on fan should be on. That might keep temps cooler.


Then I’m worried about keeping them too cool. Ambient room air temp is about 64. They are in an unheated basement.


The fan doesn’t have to be big. A small 12 volt computer fan would circulate enough air if you only have a few plants. If you have a larger fan point it somewhere other than directly at the seedlings.


100 degrees is harmless to tomatoes. Warmer temps are part of what the plants appear to need. One of the tricks I normally use in early spring is to let the greenhouse go down to about 40 degrees overnight, then the next day leave it closed so the temp goes up to 120. The cold temps stimulate early fruiting and heavy fruiting while heat the next day reverses any effect on the stems.

Based on your description, here is what I think is happening. The stem of a tomato plant transports nutrients from the roots to the leaves and photosynthate from the leaves to the roots. The stem is somewhat susceptible to low temperatures. This is dependent on a chemical named rubisco. Low temperatures deactivate rubisco producing classic symptoms of cold stress such as your plants show. Take a look at the info on my website about cold response in tomato and particularly search for “rubisco”.

The purpose of a fan on the seedlings is to produce a change in plant growth making the stems sturdier. The same effect can be achieved by running a small board over the plants a few times a day gently brushing the leaves and stems from one side to the other.


Isn’t that true with trees as well? Meaning, a new tree needs to freely stand on its own so it will be subjected to winds, which will cause it thicken up and put down deeper roots? Of course if it’s a dwarf tree, it’ll need to be supported when it starts to produce. I’m talking more about non-fruiting trees and standard/semi-standard fruit trees. Sometimes I would see trees supported on two or three sides, and wonder that it’ll get so used to external support that when that’s removed, they’ll likely tump over in a strong wind.


So the seedlings growing on the outer edges of the grow area have some yellowing and curling.

The inner ones don’t. This seems to be true for all varieties.

I think it’s a media temperature/moisture issue. Since my T5 bank is over 400 Watts, no matter how efficient it is, it’s going to produce heat.

As I said, the ambient room temperature is usually in the low to mid 60s.

At night, with th the lights off, the media temperature does fall to around that temperature. During the day, these outer seedlings’ media temps gets to maybe the mid 70s. The interior ones get to 85+. Just from “heat gain” off the lights.

While it’s my understanding that even the cooler nighttime temperatures are “acceptable” for tomatoes, they are not ideal, and moisture levels are probably staying higher on the outer edge where it stays cooler. Does that make any sense?