When Ready for Transplant, What Do I Do?

First, How Do I Know When my Seedlings are Ready for Transplant to a Bigger Pot or Tray?

When seed have been sown close together in a flat, they grow together rather quickly. They soon become overcrowded, tall and spindly (this is why seed should be sown thinly to begin with) from stretching in competition for light. You may transplant as soon as the stems are over one inch tall and the cotyledons are showing. However, after four true leaves have developed, or the plants begin to touch one another, don’t delay transplanting your seedlings into pots where they will have more space. This website includes pictures of the first true leaves for all of the different species listed, so you can check these pictures if you have doubt about whether your seedlings have true leaves or are only showing the cotyledons.

Now that My Seedlings are Ready to be Transplanted to a Pot, What Do I Do?

If you are growing your seedlings in a seed flat, you will get far superior results if you transplant your seedlings into pots or a larger, divided flat for growing on until they are ready to be planted in the garden; rather than trying to transplant the seedlings directly into the garden at this stage. If you started your seed in individual pots, you will not have to transplant, for the pots provide enough space to develop roots that will serve the young plants well when planted in the garden.

To transplant from a seedling flat, there are several simple steps to follow:

1. Water the seedling flat, using bottom watering, one hour before transplanting, so that seedlings have plenty of water in them to help withstand the shock of transplanting. You should give them a complete soak, so that soil is wet, not just moist.

2. Moisten the soil or growing mix that you will transplant the seedlings into. I recommend using a commercially prepared mix, which has been specially formulated for starting seeds and growing seedlings. Fill the pots or inserts you are using to the brim and level off the potting mix with a ruler or other straight edge. Set the pots in a tray. You may want to use a tray and pot inserts made just for transplants. Or you may simply use a large tray for growing on your transplants, though there is much greater root damage and shock when planting out into the garden from a tray, than transplanting from a pot. The root ball is much easier to keep intact in a pot than in an intermingled tray planting.

3. Dibble the growing mix in each pot by making a hole large enough to fit the seedling’s roots. Push the end of a pot label or a pencil an inch or so into the growing mix and move it back and forth to open up the hole.

4. Gently remove one seedling at a time from the flat. Use a fork or tongue depressor or old label to carefully pry the seedlings apart, as you lift them from the seedling flat. Pull them apart carefully. A small ball of growing mix should cling to the roots. Hold the seedling by the cotyledons, or seed leaves, not by the stems, in order to avoid injury to the stem; the plant can grow new leaves, but NOT a new stem!

5. Place the root ball into the hole you have made for it. Gently firm the growing mix around the roots once, then fill in the hole so that the soil surface is level in the pot. Cover only the roots and base of the stem, not the leaves, and do not worry if the potting mix is not perfectly level – the less handling of the roots at this point, the better.

6. Label the pots with the name of the plant, the date sown and the date transplanted. Of course, if you used a label when you first planted your seed, you can simply add the transplant date to the original label.

7. Thoroughly soak with water with a little fertilizer in it, from the bottom, the same way as for a seedling flat.


Gardeners' Quotes

"Digging up a mature clump of perennials, separating it into segments with new stems and roots and discarding the old core is an effective way to keep plants vigorous, free-flowering and disease-free," Adrian Higgins, The Washington Post Garden Book