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1) Growth State: best when inactive or dormant

2) Susceptibility to winter injury: for plants easily damaged by winter freezes

  • prune after cold of winter  
  • remove all winter killed tissue
  • you may need to allow some spring growth to tell if tissue is dead or not.  
3) Time of flower bud formation on flowering plants:
    a) spring flowering plants:
    • flower on last years growth (2 year old wood); i.e. flower buds present since last summer or fall.
    • therefore, prune right after flowering in spring and before new buds form.  

    b) summer or fall flowering plants:

    • flower on current years growth (1 year old wood); i.e. flower buds form on new growth of current year.  
    • therefore, prune fall, winter or early spring, but best to prune after cold of winter and before new growth starts in spring.  
4) Transplanting: pruning should be to equalize root/shoot ratio, thus, decrease transplanting shock.
    To equalize root/shoot ratio:
    a) thin-out immediately after or at the time of transplanting 
    b) root prune before transplanting (months to years). 

Chemicals that selectively kill or disrupt shoot tips to remove apical dominance. 
1) Atrinal 
2) Off-Shoot-0 
3) Maleic hydrazide 
4) Emgard 2007