When & How to Pot Up Seedlings

“Potting up” seedlings means just that, “upping the size of the pot” the seedling is grown in. Depending on the size of the pot the seeds were started in, you may or may not have to pot up your seedlings before transplanting them into the garden. 

Ideally, seedlings are planted directly into the garden rather than moving into larger containers. However, moving seedlings to larger containers is helpful for crops that have outgrown the containers they were started in, but the timing isn’t right for planting outside.

Roots restricted in too-small containers become “root bound” and are less likely to flourish after being planted in the garden. 

A larger container allows seedlings to live happily longer in the ideal conditions of your seed-starting area. More room in the container provides additional space for the roots to absorb moisture and nutrients from fresh soil.  

When to pot up seedlings: 

• When you notice that their growth seems to have slowed or stopped. Gently remove the seedling from the container and check on the roots; they may circulate in the pot or take up all available space inside the container. 
• It’s time to move seedlings to a larger container when the roots extend outside the container.
• Seedlings that are becoming crowded or too close to one another. Each plant will grow better with additional room.

How to deal with root-bound plants:

• Loosen coiled roots. Using your hands, gently tease the roots apart. Trim back any extra-long roots.
• If the roots won’t loosen, spray the soil away with water first and then uncoil the roots.
• If the roots still won’t untangle. Make several vertical slits in the root ball with a knife to stimulate the growth of new roots before planting.

How to pot up seedlings:

1. Gather supplies

Container – Choose a container at least twice as large as the current pot. For potting up, I use these 5.5-inch nursery pots. Ensure containers are clean before using them.

Soil – Use slightly-moistened potting soil. I use the Growing in the Garden Raised Bed Mix to pot up my seedlings. If desired, you can use a mixture of raised bed mix or potting soil and seed starting mix. 

Labels – You may need more if moving from rows or six-packs into individual containers. When plants are in larger containers, give each plant its own label.

2. Know whether or not to bury the stem when repotting

Some seedlings can be buried deeper to encourage a strong stem and root development. Other plants need to be transplanted at the same level as the original container to avoid rotting the stem. 

3. Pot seedlings into a new container

• Fill the bottom of the container with soil.
• Tip over the seedling and gently dump it into your hand. Hold the stem carefully between your fingers. A plant can grow new leaves or roots, but won’t recover from a damaged stem.
• Place the seedling on top of the layer of soil.
• Gently fill in and firm soil around the seedling. 

4. Water and feed newly-potted seedlings

• Water seedlings and fill in any gaps in the soil.
• Feed with a half-dose of seaweed fertilizer. 

5. Care for seedlings until it’s time to transplant them into the garden

• Continue providing light and air circulation.
• Water seedlings from the bottom as needed.
• Feed weekly with a half-dose seaweed fertilizer. (To feed seedlings, add 1/2 dose of fertilizer to the water once a week before watering the seedlings.)
• Harden off seedlings before transplanting outside.

This post will be helpful if you’re looking for more information about how to start seeds indoors.

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