Many people have asked so I thought I would dedicate a blog post to "potting up". Essentially potting up happens when you have seedlings outgrow their initial pots or plugs and aren't ready to go outside yet.
I start my seeds in two cycles. The early (end of January/beginning of February) seeds. Those are my peppers, celery, cabbage, cauliflower, and some of my flower seeds (snapdragons, petunias, marigolds, and zinnias) when I want to have some early flowers. Often these plants outgrow their initial pots and need to be potted up or transplanted into bigger pots before it is warm enough for me to place them in the garden. Or because I haven't gotten the beds prepared early enough to transplant them.
Depending on how you started your seeds, you may need to pot up at different times. for example, if you used the small plugs that some propagation trays use, you may need to pot up sooner than someone who used a 2-inch square pot. So how do you know when it's time to pot up?
I am sure that there are many ways to figure this out but here is my method. I use the 2-inch square pots that I reuse from the nursery seedlings I have purchased so I am basing my methods on that fact. If you use plugs or peat pucks, you might need to pot up sooner.
First, if you plant multiple seeds in your pots like I do (usually I plant 3 unless the seeds are super small, then there are definitely more than 3-see photo below), you are supposed to pull out the two weakest plants and keep the third one. Being who I am, I just can't waste a perfectly good seedling. So once my seedlings are about 1-2 inches tall, I usually separate them so that they aren't competing for nutrients. I put each seedling back into a 2-inch square pot on its own.
As you can see, I didn't use the "only 3 rule" with my tomato seeds. That's because I usually just squirt a grape tomato into the dirt and then divide them out once they have germinated.
My pepper seeds were much more civilized with at most 3 seeds to a pot to start. As you can see the first set of leaves look pretty similar on most plants.
Once they are in their separate pots, they will start to grow bigger and develop a second and third set of leaves. Once they do this, it might be time to pot up again.
I should note that when I first planted my seeds, I used a seedling soil mix in the top half and a regular ( Miracle-Gro All-Purpose Potting Soil). When I pot up, I only use the Miracle-Gro All-Purpose Potting Soil from now on. The Miracle-Gro potting soil has nutrients built into it and therefore, I don't have to add any other fertilizer before I transplant them outdoors.
When determining if I need to pot up again, I look for a second (and potentially a third) set of leaves on my seedling. These are the leaves that come after the initial leaves at the start of germination.
I potted up this pepper plant from a 2-in square pot to a 3.5 inch round pot. I purchased the pots from Amazon (they would out to be about $0.16 each). I also purchased these 4-inch pots in case I need to pot up again. These pots stack well and are very flexible. Some people comment that they feel flimsy but I actually like the flexibility it has so when I pop my plants out, I don't crack the plastic. 100 pots stack very neatly and don't take up a lot of room either. Something I really appreciate in the off-season. I also reuse those I get from the nursery plants I have purchased in the past.
This pot was overcrowded and needed to be divided up. With small plants like this, I tend to break the clump into two or three parts instead of trying to separate them individually, partly because it is finicky, and also I don't want to use up 20 pots before I put them outside. Once I plant them outside, I will divide them up even more.
Third, I look for roots that are starting to pop out of the bottom of the pot. This is a sign that the plant could become root-bound.
This plant was becoming root-bound and some roots were starting to poke out the bottom of the pot. I repotted this one into a 4-inch pot to give it more room to grow.
My pepper plants will probably need to be potted up at least once more-most likely to a one-gallon pot before I take them outside (which won't be until May).
Although I am a joyful gardener, I am not a very patient one. Sometimes I plant seeds way too early and start to run out of room in my indoor grow area. This year, I planted grape tomatoes in the first round and they have taken off. They are now poking through the shelf above. I will have to pot them up or pinch them off to keep them viable until it is warm enough to take them out safely.
The plants I potted up on the left shot up because they had more room to grow. The tomato plants on the right haven't been potted up yet. As you can see, they haven't grown as big and are most likely root-bound. I will need to repot them soon.
Lessons learned:
when determining if you need to pot up, look for overcrowding of plants (too many plants in a pot), a second or third set of leaves, and/or roots poking out the bottom of your pot
use all-purpose potting soil such as Miracle-Gro when you pot up
be prepared to pot up a few times for those plants that need to be started early but can't go outside until there are consistently warm temperatures both at night and during the day
purchase pots that stack easily and have flexibility so they don't crack when you are trying to remove plants from them
reuse pots whenever you can
Whenever I have to pot up plants, I find joy in the fact that my plants are thriving and will soon be growing outdoors. While potting up can be a messy process, it's definitely worth the effort to ensure that your plants continue to grow and develop properly.
Happy gardening!
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