They're getting so tall! With neat little leaves!
this post was submitted on 26 Apr 2025
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What kind?
Pro-tip though, those started containers should probably be a 4" at minimum to get hearty tomato stems before transplanting. Those look to be about 1".
I've used the 2" six slot trays to great effect all the time. All the tomatoes I've transplanted from those this year are doing awesome. Why would it need to be 4"?
Ran a specialty growing operation for years, and there's a reason nurseries keep specific starter cell size for specific plants.
I've done tests to see if we could increase yield by using smaller starter cells: 1", 2", 4", 6". The difference is drastic. When your cells are too shallow, you end up with what this picture shows here: height, but not much structural growth outward. With tomatoes the goal is get a certain amount of branching outward before it's healthy enough to transplant, and that's usually two branches top leaves, but the width of the stem is also important.
If you start in cells that are too shallow, they get root bound and grow up, but not out much as seen here. If you give it enough space, you'll get both because the plant has extra room to expand: first outward, then upward. The large the root ball, the more energy can be expended upward for growth.
So while you CAN use smaller cells, you'll always get the tall, thin types of starters as seen in this picture, not the same hearty growth you get from nursery plants. They may do fine, sure, but transplanting with a hearty plant means less time to adjust after planting before getting enough steam to really expand and branch out.
Running a specialty grow without basic knowledge of plant physiology.... Yep checks out.
The reason they are so tall is because of low light levels. With lower light levels the interplant competition causes them to stretch taller. More space under the same light levels would have a much shorter plant.
So what they need, more light. Specifically hardening off outside would be best.
They also need to be knocked around a bit by wind or mechanically to trigger stem thickening and lignin formation.
FYI commercial transplanters for thousands of commercial hectares around the globe usually use a 256 cell tray. I have also seen them use a 512 tray.
It also doesn't matter if tomato transplants get root bound. They are stem rooters. Transplant a 8" tall seedling with 6" of the stem buried and the entire 6" of stem will form roots.
Also transplanting with a larger plant usually means more severe transplant shock. A smaller plant generally adapts faster, grows a more balanced root system and produces more.
Yup. These guys are stretching to find light, trying to be taller than their neighbors.
Indoor growers keep fans on to simulate wind and stimulate stem strength. I just put my sprouts in front of an open window and rotate once or twice a day so that they don't grow sideways.
I usually transfer them to new containers when the roots hit the bottom so they don't get root bound, but I guess that would take more time than starting from deeper pots.
Oh? Should I move them to bigger pots then? They're san marzano tomatoes!
You can also plant tomato seedlings much deeper as they will grow roots from the stem. Plant them all the way down to their first true leaves. That’s what I’ve read at least.
San Marzano, best. Well you shouldn't move them now as the root will be pretty fragile, but if you want starters that are as tall and hearty as a nursery would sell, you'll just need to start them in a bigger starter next year. It helps them to be more resilient to the initial shock of transplanting, and will make root ball damage less like as it will have more room to develop.
Okay! Next year, deeper tray thingies! Good to know!
Deeper and wider! You need both. Go look at how nurseries sell them, and you'll see what I mean. Almost always in a 4" cell, and look more mature at the same age versus smaller cell types like these 👍
Nurseries sell them like that because they can charge higher prices. Poorly informed consumers pick the larger plants thinking they will grow better. It's also easier for retailers to keep them wet very few of them have watering systems setup for them.
You can read my other comment, but that's simply not true 🤣
Was a grower for years, and they sell them like that because there's less chance of issues during transplanting. Hearty plants, less transplant problems, happier customers.
I did respond to your other comment. Sorry bud, basic plant physiology and thousands of hectares of commercial production disagrees with everything you wrote.