How to Thin Out Seedlings



Thinning out, also known as pricking out, means removing seedlings from their original container and replanting in individual cells or pots to give them more growing room. The method shown here applies to all seedlings.

Steps

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    Know when the seedlings are ready to be thinned out. Seedlings need to be thinned out when their leaves begin to touch their neighbor. As a general rule, this is when they have sprouted their second set of leaves. This is called the true leaf stage, with the first set being the seed leaves. If they are left too long in an overcrowded tray, the top growth of each seedling will become lank and weak.
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    Prepare the soil.
    • Sieve the soil onto a flat surface to break up any lumps.
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    • Fill the tray or pots with soil, using your hands to work it into the individual cells.
    • Tap the tray to work the soil into the corners.
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    Separate the seedlings.
    • Insert the dibber into the soil at the edge of the seedling tray.
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    • Lever it back to loosen the soil under the seedlings and gently tease them out.
    • Carefully separate the seedlings by holding them by the leaves. Avoid handling by the stem or the roots as they are both easily damaged.
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    Select the strongest looking seedlings with the biggest root system. Discard the more spindly looking ones with the smaller root systems as they are less likely to survive.
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    Replant.
    • With the dibber, create a large hole deep and wide enough to hold the root system.
    • Lower a seedling in and firm the soil around it.
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    Label. Use an indelible pen to put the plant variety on one side, and the date on the other. Place this at the edge of the tray.
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    Water. Turn the rose on the watering can upwards, this prevents disruption to the soil's surface. Water heavily.
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    Leave to grow. Different seeds require different growing conditions. Check the seed packet. If your seedlings will eventually be planted outside, place them in an unheated greenhouse or cold frame, or outside in an area that is protected from direct sunlight and heavy winds. This will gently acclimatize the seedlings to outside conditions. When they have sprouted 3 or 4 pairs of leaves, they are ready to be replanted into display containers or transplanted into the ground.
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    Finished.

Tips

  • All supplies should be obtainable from your local nursery or plant store.
  • Keep a record of seedlings planted from year to year in a gardening journal; this will help you to establish patterns of best plants, best times of year to transplant, best areas of the garden for planting etc.

Things You'll Need

  • some seedlings
  • modular cell tray / pots
  • a sieve
  • some soil, of the right pH balance - check the seed packet for soil pH
  • a dibber (or a pencil, ice cream stick etc.)
  • a watering can with a rose attachment
  • some plant labels
  • an indelible pen

Sources and Citations

  • VideoJug A video demonstration of thinning out seedlings, featuring Tom Cole. Original source of article; shared with permission and appreciation.

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