If you start seeds in flats and you're into container gardening, transplant when seedlings are still very young. Watch for the emergence of the first pair of true leaves and transplant soon after. The choice of planting containers ranges from homemade newspaper cylinders to plastic cell packs and clay pots. Peat pots are a favorite of many gardeners, because the pots can be transplanted with the plant, but we recommend avoiding peat because of the unsustainable nature of the peat industry. Plastic and clay containers are reusable.
Before you start, collect your transplanting supplies and put down a layer of newspaper to catch spills. Follow these steps:
Fill the containers with soil mix. Either buy bags of mix (be aware that these may contain synthetic chemical fertilizer) or make your own seed-starting mix by combining one part vermiculite or perlite with one part peat moss, milled sphagnum moss, coir, or well-screened compost. The depth of the soil depends on seedling size: Fill nearly to the top for small seedlings; start with only 1 inch of soil for large ones, since you fill the pots as you transplant.
Pour warm water onto the soil mix, and let it sit for an hour to soak in. Moist potting soil prevents seedling roots from drying out.
Related: How To Start Seeds
Carefully dig out either individual seedlings or small groups of seedlings. A Popsicle stick makes a good all-purpose tool for digging, lifting, and moving tiny plants. A tablespoon or narrow trowel works well for larger transplants.
Hold each seedling by one of the leaves, as shown, not by (or around) the stem: You could crush the tender stem, or if you grasp the stem tip, you could kill the growing point and ruin the seedling’s further growth.
For very young seedlings, poke small holes into the soil mix with a pencil. For larger seedlings, hold the plant in the pot while you fill in around the roots with soil. Firm the soil gently with your fingertips.
Related: 5 Reasons You Should Start Your Own Seeds Instead Of Buying Seedlings
Return the seedlings to the window, light rack, or cold frame. If seedlings wilt from the stress of transplanting, mist lightly with water and cover loosely with a sheet of plastic wrap. Keep them cool and out of direct sun for a day or two, them remove wrap and return to the light.
Keep soil lightly moist but not soggy by pouring water into the tray holding the containers. Feed regularly with a weak solution of water-soluble organic fertilizer.
As the plants grow, pinch or snip off any extra seedlings, leaving only the strongest one.
If you miscalculated the seed-starting date or if the weather turns nasty, you may need to transplant your plants again to larger containers so they won’t stop growing and become stunted. Roots pushing through drainage holes are a clue that it’s time to transplant.
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