Seeds Series: Dividing and Potting Up

  • Difficulty Rating: Beginner


Plant in Pot

Now that your seeds have sprouted and green growth is filling up every inch of your seedling trays, what’s next?

It’s time to start potting up your seedlings!

Usually when we sow seeds – whether in a container or directly into the soil – more seeds are planted than will thrive in each square inch of soil. This happens for a number of reasons. Seeds may be tiny and difficult to insert one-by-one. Or, even if we did seed them individually and perfectly, they may move about when we water them. And, really, most seed is relatively inexpensive, so it can be cost effective to seed more than we will need and thin out the extras later.

Consider this: if we plant only one miniscule tomato seed into a large growing pot and that seed never germinates (aka it doesn’t grow at all), we may completely miss out on growing tomatoes that season. Timing is critical! However, if we thickly plant many seeds in a small container, knowing we can divide and transplant them later, we have a better chance of meeting our calendar requirements and getting a number of plants to choose from rather than none at all.

Wondering why we need transplant those crowded seedlings into new pots at all? There are a number of reasons, including:

  • If you followed our suggestions in our “Tools for the Trade”, then your seedlings germinated in a soil-like mixture that is nutrient-free – and sterile. Now that your plants are beginning to grow and feed themselves via photosynthesis, their roots are searching for nutrients found in soil that help them grow and stay healthy. Transplanting your sprouts and beginning to offer them supplemental fertilization – whether a packaged fertilizer or a glob of homemade compost or vermicompost – will provide for these needs. Sterile starter mix won’t.
  • Since your young seedlings are crowded in a small container, they are all fighting for space and resources. Keeping too many plants knotted together in a single small pot may lead to the demise of all. Airflow will be reduced, which can provide a perfect environment for fungal infections. Lots of roots wrapped together may mean the soil dries out fast as plants compete for limited resources.


Potted plant with label


Determining when to begin potting up your plants can be a challenge. Some seedlings are quite tiny, which makes handling them difficult. Others are larger and heartier. Ideally, begin transplanting your youngsters to larger containers once they have formed two (or more) sets of true leaves. The first leaves that come up from the soil may look nothing like the final plant. Wait for a couple pair of leaves that “look right” to form, and then begin the task of potting up.

Then prepare several containers will a high quality potting mix. Water the filled containers until the soil is saturated. (Using warm water on a cold day can expedite this process.) Be sure your soil is moist but well drained before you begin dividing your seedlings to transplant them. Next, use your finger to create a hole in each pot where you will insert a seedling.

To separate your seedlings, gently squeeze all sides of their original growing container to loosen them slightly. Then, gently tilt the container and break apart a section of the growth. Holding the top growth of an individual sprout, gently tease it away from the other sprouts. Working with bare hands may make this job easier, but avoid touching the roots as this may immediately dry them and kill your plant.

Carefully insert each seedling, root down, into your prepared containers. Cover any exposed roots with soil as you go.  Don’t beat yourself up if you lose a few seedlings along the way. Even a seasoned pro feeds several seedlings to the compost pile during transplanting! That’s another reason we sow more than we’ll need; losing a few plants along the way is going to happen.

Once you have finished transplanting, be sure to water everything thoroughly. If you are working on a hot day, you may want to water each pot as you plant. If it is colder, watering once you’re done may suffice. If you haven’t included compost or other nutrients in your soil blend, be sure to add a bit of fertilizer to your plants before or as you water (using the manufacturer’s guidelines for amount and frequency going forward).


Potted plant with label


As you work, be sure to label your plants! If you fill a tray with all of the same kind of plant, one label may be sufficient. If you mix several different containers of plantings into one tray full, be sure you label each unique pot as you work.  To help keep track of what happened when, I like to keep notes on the label showing original seeding date and each time I transplant or pot up a plant.

Depending on your climate and type of plant you are potting up, what you do with your transplants may vary. If your seedlings germinated during warm weather, it may suffice to set them aside in a protected location. If you are working in cold weather, your plants may need to be placed under lights indoors again. Too, you may wish to cover your trays with vented plastic covers again to help them root in and grow strongly.

Next time in this series: Hardening Off Seedlings

Last time in this series: Seed Starting Tools & Tips