Backyard Aquaponics
A place to discuss aquaponics

I'm growing a variety of tomato plants and am having a problem with the stems pinching and the plant collapsing. I've had at least one from each variety be affected (except my brandywines).
It doesn't seem to be limited to the tallest stems or the plants with the most leaves.
They are in my greenhouse and get plenty of sunlight.

I think the problem may be that I waited too long to get the seedlings into full sun and they ended up stretching as seedlings and not developing a strong stem. The leaf growth then surpassed the stem strength and they collapsed. This stem collapse problem started occurring about a week or two after transplanting and putting in the greenhouse.

I have another batch of seedlings that have sprouted and want to avoid this from happening.
Any input is greatly appreciated!

I partially buried the stems which created more of a root system. To stop them falling over you could use skewers/paddlepop sticks, or something like that to create a mini support system around the seedlings?

Can't get them into the light earlier?

I have noticed the exact same thing with my Spinach seedlings.... I think it's related to them being leggy due to a lack of sunlight even though mine get a reasonable amount, clearly not enough since they're all reaching for the sky!

+1 for deep stem planting horticulturists have started to use this technique for trees as well, giveing the plants deeper root growth & stronger stems

I can get them in the sun as soon as they sprout, but I thought seedlings were supposed to be gradually introduced to full sun.
I'm currently watching a lot of youtube about transplanting and hardening seedlings.

I like the idea of giving them a mini trellis. Do you think I can save the ones that have already fallen over?

I did bury the stem when I transplanted, maybe I need to bury them even farther.

I can get them in the sun as soon as they sprout, but I thought seedlings were supposed to be gradually introduced to full sun.
I'm currently watching a lot of youtube about transplanting and hardening seedlings.

I like the idea of giving them a mini trellis. Do you think I can save the ones that have already fallen over?

I did bury the stem when I transplanted, maybe I need to bury them even farther.

In potting mix it is important not to over water if it is wet they can rot at the soil air line and then fall over as yours have.

Good point, I'll keep that in mind.
These pictures were taken right after watering.
I have been watering once every three days and the soil is usually very dry after three days.

I think the hardening off is if you've got a harsh sun.

I couldn't imagine it's too harsh in Florida atm.

Mine happily sprout outside in full summer time Australian sun.

I have a diffusive covering, maybe I don't need to harden off at all.

I've started the second batch in the sun and will see how they fare.

Hi Stonewall,

I noticed most of the pinching was around ground level so this could be damping off (seems very likely to me). You may be giving them too much water.

http://www.ipm.ucdavis.edu/PMG/r783103111.html
http://ucanr.edu/sites/scmg/files/29785.pdf

They do look like they need a bit more light as others have mentioned. Give them some shade when you put them out in the sun at first to help harden them off. If it's getting cold at night you may have to bring them in - whatever you do just make the change gradual so they can adjust.

I agree with Scotty...dampening off. It can be a soil borne bacteria that will affect the next batch if not using new, sterile media. I have had good luck with 3% hydrogen peroxide mixed 1 to 10 parts water and sprayed on the top of the soil. It has never affected plants so far.

Looks like Pythium or Ryzoc to me. Remove, replant, and treat with Garden Friendly fungicide as a drench. Increase sun, and decrease water a bit.

Those are all lumped together and termed Dampening Off- as Scotty and Rairdog said.