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Horticulture 1000
HT1021 - Practical skills - Thinning seedlings

Thinning seedlings

Thinning out is reducing the number of seedlings in a  crowded row. Plants grown from seeds sown directly in the ground are often  overcrowded. To grow into useful sized plants, each plant needs room to spread  its roots and leaves. If it doesn't have room there will be competition for  light, water and nutrients. The plant will grow long and spindly and won't develop  to its full potential.

When some crops are thinned, such as lettuce or  cabbage, the seedlings can be transplanted elsewhere.

With most root crops, for example, radish, carrot,  parsnip and beetroot, transplanting doesn't work very well. The thinnings are  composted or eaten.

Before  thinning out seedlings, make sure the soil is moist. The seedlings to be  removed are easier to pull out and the remaining seedlings are less likely to  be damaged.

When thinning out seedlings, remove the weakest plants  and leave the strongest ones.
    Work out the expected full size of the strongest  plants and the space that they will need, and then pull out the seedlings  growing in between.

A good time to thin out is when it's raining. If this  isn't possible, thin out in the early evening after the heat of the day has  passed and water each row immediately after thinning. Water helps to rinse the  disturbed soil back round the roots of the remaining plants.

Carrot seedlings to be thinned Carrot seedlings to be thinned.
Radish seedlings to be thinned Radish seedlings to be thinned.

Key points   Key points

  • Thinning out is reducing seedlings in a crowded  row.
  • Thinning out creates more space for seedlings to  grow.
  • Thinning out reduces competition for light,  water and nutrients.
  • When thinning, leave the strongest plants.
  • Watering after thinning helps rinse the  disturbed soil back around the roots.

Remember to return your labelled diary to  your teacher for checking along with your completed workbook.

To complete the internally assessed  practical skills standard AS90157 you need to complete all the following tasks:

  • Cuttings HT1022Y1
  • Grafting HT107Y1
  • Pruning HT1024Y1
  • Recognition HT110Y1.

You will need to have completed the work for Practical skills HT1021 along with the rest of the HT1000 course before you attempt  the recognition task HT110Y1.

What's next?

  1. Complete the assessment form and cover sheet.
  2. Return these along with your labelled diary and workbook to your teacher.
  3. Contact your teacher to discuss your study.