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When Should I Transplant Tomato Seedlings Into Larger Containers?


When to transplant tomato seedlings into larger containers is a question that every gardener watches for every year. While the answer isn't always the same, there are some general guidelines to follow when determining how large your plants need to be before they're ready for their next stage of growth. In this article we'll talk about when you should start transplanting your tomato seedlings, how big they need to be before moving them, and what type of potting soil works best for growing tomatoes indoors or outside.


Why do I need to transplant tomato seedlings into a larger container?


Transplanting your tomato seedlings is important because the roots will get bound up in the small container and stunt the plant's growth ("root-bound"). If you have a root-bound plant, it won't be able to develop properly, and that could lead to other plant health problems down the road. For example, root-bound plants are also more susceptible to disease and pests because they won't be able to produce enough energy or nutrients for their immune system functions. They may also not flower well either—or at all! And if they do flower, their fruit yield may suffer too as they don't have enough energy or nutrients to give out with each flower bud.


The important signs to look when transplanting tomato seedlings into larger containers.


When you see your seedling's first "true leaves," it’s time to transplant. True leaves are the ones that emerge after the seedling’s first sprout leaves (it's "cotyledon" leaves). The true leaves are larger and more developed than cotyledons, which are embryonic leaves that grow out of a seed before any other growth takes place.


True leaves can be anywhere from two to 20 on tomato plants, depending on how many seeds you planted in each cell or pot. The first true leaf is usually larger than subsequent ones—though this isn't always the case! It may also have some reddish spotting on its surface if you've used a variety that has red fruit coloration (like 'Red Robin'!)


When your seedling grows to 4-5" tall.


Another sign is when your plant grows 4-5" tall. When your seedling grows to 4-5" tall, it is ready for transplanting. I have had tomato seedlings that shot up to upwards of 5 inches without any sign of true leaves (although rare). In any event, the roots need room to grow and if you wait too long, the plant will become root-bound because of its restricted space. If you don’t wait long enough, then the roots will get bound up in the small container and strangle themselves.


Summary of how to know when it's time to transplant your seedlings into bigger containers:


When it's time to transplant tomato plants, you have a few options. You can wait until they're big enough to plant in the ground (this is called "planting out"), but that can take weeks or months. They'll grow more quickly in larger pots with better soil, so transplant them before they get too big for their britches!


Here are some signs that it might be time for your seedlings to move on up:

  • When they're 4-5" tall and their first true leaves appear, which usually happens within 2-3 weeks after germination.

  • When roots start to wrap around the root ball or when plants begin falling over from lack of support (you may need to stake them).

  • After plants have been growing in their small pots for two months or more—and especially if you've had any trouble with fungus gnats breeding under those little pots!

Get transplanting!


So there you have it! When to transplant a tomato seedling into bigger containers. The important thing is not to transplant too soon or too late, and make sure that your plant gets the right amount of water, nutrients and sunlight every step of the way.


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