My buddy not too far away is growing tomatoes and we regularly talk about the progress of our plants. We both put the sets out at about the same time, end of February to first part of March. Our plants are about the same height taken into consideration cultivar. The amount and timing of the fruit set is roughly similar.

The main difference, and I haven’t seen his plants in person, is he says his main stems are about the diameter of Kennedy Half dollar. I don’t know if he’s putting me on or just over estimating or it is the truth, but my tomato main stems are about one US quarter in diameter at best and mostly more like a nickel.

We are feeding different fertilizer, so maybe that’s part of it. I don’t know the exact light conditions at his place.

Anyway, what’s your experience with tomato stems and what do you consider ideal, if there is an ideal? What accounts for differences in stem diameter beyond obvious differences in tomato varieties? What does thicker tomato stems say about the fertilizer regimen?

I thought my stems looked great this year and my plants all look good and disease free so far, but should I be looking to beef the stems up next time around?

Very curious about this myself--this year my stems are the thickest I've ever seen. However, this seems to be true only in my raised beds, all of which had 5-10 inches of composted cow manure that I got for Christmas from my father-in-law tilled in. The ones in containers look more "normal". I suspect that it's fertilizer/soil related, and maybe partly due to generally good weather, but don't have anything more to offer than anecdotes.

I've found that early environmental affects on the seedlings can cause the plant to develope differently too. Starting them in cooler air, keeping a fan on them, or even "tickling" them will make the seedlings grow stouter. My wife jokes when i tickle my plants. But it works!

The plants will grow thicker even after you take them outside.

Rockoe10 wrote: ↑Fri Apr 23, 2021 12:34 pm I've found that early environmental affects on the seedlings can cause the plant to develope differently too. Starting them in cooler air, keeping a fan on them, or even "tickling" them will make the seedlings grow stouter. My wife jokes when i tickle my plants. But it works!

The plants will grow thicker even after you take them outside.

I put a small fan on my seedlings this year for the first time, but didn't expect that to have a longer term difference. The DID look a lot better when I put them in than usual, however.

I recommend researching "Thigmomorphogenesis". It's a pretty rad phenomena

Interesting. I’ve never seen tomato stems that big around ... mine are not. Any idea as to whether it’s all of his plants or just one variety?

Wow, I'd wanna put an eyeball on those plants of his! Just to make sure, ya know....

Working on getting a photo

Thinner stems could also be a result of simple shade avoidance response https://en.wikipedia.org/wiki/Shade_avoidance. Plants sense the shading of close by plants by ”measuring” the amount of far red light. Far red light enriches (in comparison to normal red light) when there is another plant close or shading. Plants don’t have eyes or nervous system but they have some type of photo sensors to sense the environment. The shade or the reflection of light from a non-living object is different than from another plant. Plants actually ”know” if there is someone close by and if that someone is another plant. One strategy to compete is to grow faster with thinner stems.

Tomato may have quite strong shade avoidance response like stem elongation e.g. if the seedlings are grown in high density, low light and high temperature. Or if they are planted too close each other - or are shaded by other plants for some other reason.

I have seen plenty of thin tomato plants in my life. My green house looks much bigger at the planting time than it actually is. And I tend to be very optimistic when I squeeze ”one more” tomato in. Sadly, it is never just one.

Soil or fert-wise, I believe it's a higher potassium that produces thicker stems. If you combine that nutrient balance with cooler temps, wind or thigmo, and wide spacing ie plenty of light and no shade effects, you can probably get the big stems your friend is talking about.
Do you want bigger stems?
If you had a problem with plant fragility, being unable to bear the fruit weight or random weather conditions, then maybe it is worthwhile to beef up the stems. If you didn't have much of a problem, then it really isn't necessary.
All indeterminate tomatoes need support anyway.... I've never seen thick enough stems to stand upright without strings attached.

Thingmomorphogensis , reckon that's why I never grew over six foot. Parents scruffing my hair as a little kid.

Texas has wind in spades no doubt so that Thigmomorphogenesis thing could be done naturally without any human intervention or fans or mechanical shaking. My buddy lives directly on Clear Lake, an arm of Galveston Bay, in a sailing oriented community. There is nothing at his place really to block the frequent gusts off the water except maybe sailboat masts. Plus, he stakes out his tomato plants instead of using rigid metal cages so those gusts and winds whipping off the lake make his plants dance. Maybe he has the perfect conditions to create muscular tomato stems. Still waiting for his stem photos.

This season, I used pretty light weight, small diameter portions of bamboo to stake out my tomatoes. Those stakes flex a bunch in strong winds like we often have, like yesterday in particular. I thought my less crowded tomato plants, ones I gave a little more room looked especially robust in the stem department this year.

He and I are both marveling at the vigor and health of our tomato plants this time around so perhaps the weather conditions have been extra good.

These are some of my tomato stems with a penny as a reference, stems which look robust enough to me, but not out of the ordinary. I tend to crowd my plants a bit so I wouldn’t expect them to get super thick.

Pineapple, Mortgage Lifter, Blue Ribbon, and Big Beef are these varieties.

Buddy swears he will send me some photos.

My buddy sends this photo, nothing really to do with stems, although I think I see an ordinary main stem in the background. Pretty looking Black Krim tomatoes, though.

But, hey, we got the word and concept Thingmomorphogensis introduced into a thread so I call that a win.

https://c.tenor.com/qGM0NI-m_rgAAAAM/th ... w-more.gif

They may not be the diameter of a silver dollar, but they are wonderfully healthy looking plants!

I have researched the topic of stem thickness, and I can't find any clear conclusion. It's obviously related to nutrition, but which element exactly? It seems mostly about N and P, and some plant hormones.
I think the P and N values are certainly very important, I notice that during good elongation of the stem coupled with dark leaf (so signs of good P and N, without being limited by some micronutrient), the stem also is thickest.