Hand thinning of apple flowers

Hand thinning of flower clusters is rarely if ever carried out in mature commercial orchards. Hand thinning is too labour intensive and hence too expensive.

However, experiments conducted in Germany (Link, 1998) have shown the clear benefits of early hand thinning.  Experiments conducted in Switzerland on Elstar trees, which were exhibiting pronounced biennial bearing, also showed the advantages of hand thinning of blossoms (Bertschinger et al.,).

  • The work demonstrated that biennial bearing of Elstar could best be avoided by removal of 2/3 of the flower clusters on the entire tree in the first year of treatment coupled with some further fruitlet thinning (hand or use of NAA) after June Drop in subsequent years.
  • Also effective, was removal of all the flower clusters from half the tree in the first year of treatment, again coupled with subsequent hand thinning of fruitlets.
  • This latter option is best for organic Elstar production, as it involves no use of chemical thinners.
  • Approximately 8‑10 minutes were needed to remove all the clusters on 50% of a tree (250 hours/ha if 1500 trees/ha) in the first year of treatments.
  • The subsequent treatments took on average 3 minutes per tree.
  • The fruits from the trees on which clusters were removed from 50% of the tree canopy proved to be the firmest.

The biennial bearing variety Boskoop also benefits from very early hand thinning in the ‘on’ year.

  • For good return bloom in the subsequent season flower thinning had to be completed in the first two weeks following flowering (Tromp, 2000).

Hand thinning of blossoms is occasionally practised on newly planted trees so as to prevent fruit set and encourage shoot growth to fill the allotted canopy space.

  • Hand thinning of flowers has the advantages that it is environmentally sensitive (uses no chemicals) and allows competition between developing fruitlets to be reduced at the earliest opportunity.
  • However, hand thinning of flower clusters is rarely if ever carried out in mature commercial orchards. It is too labour intensive and hence too expensive.