Transcript Slide 1
Nursery Pruning/Training Winston Dunwell April 1, 2010 http://www.ca.uky.edu/HLA/Dunwell/win1.html Pruning is the selective removal of part of a plant's top growth, namely branches and shoots, or part of its bottom growth, the roots, so as to control subsequent plant growth and behavior. If branches are removed, the hormones (auxins) and complex metabolites, made by leaves and buds, will not be as plentiful and this will reduce root growth. If roots are removed, the flow of nutrients from the soil and the supply of hormones (cytokinin) and storage compounds from the roots will all be reduced. If these are not so readily available to buds on the shoot system their growth will be controlled. Apical Dominance The apical bud usually grows with greater vigor and is larger than lateral or axillary buds occurring on the stem below. The apex exerts a controlling influence over the shoot, and suppresses the growth of lateral buds. If the tip is removed the apical dominance is broken and one of the buds below the apex will begin to grow and become the new leader; this one establishes its own dominance over the other buds. Shoot tip is removed Cytokinins, water and mineral salts continue to pass up from the roots. Hormone accumulates in the upper part of the severed shoot where it stimulates young cells (and adventitious buds). Most likely to respond are in the youngest bud, that which is nearest the tip. The cells begin to divide, produce auxin and establish their xylem connection to the main system. In due course they develop as the replacement leading shoot. Training high clearance street trees Hydraulic pruners open and close at the speed related to the pressure applied versus the pneumatic that snap closed when the lever is pressed. Hydraulic system for pruning budded field trees Pneumatic system for nursery pruning Pneumatic pruners commonly used in large orchards Common to shade tree nursery training – Hand pruners and masking tape for training leaders Highly respected publication Prune to: A bud A branch the main trunk Or the ground English publication but common to nursery libraries Much of the landscape pruning is due to poor plant selection or lack of proper training in the nursery. Excurrent Growth Habit strong central leader Decurrent Growth Habit – weak central leader One dominant leader structure with: Branch diameter no more than 1/2 to 2/3 trunk diameter. No large-diameter branches growing below the final canopy Co-dominant leader with included bark = poor form and potential hazard. Cannot be fixed – destroy rather than invest. Co-dominant Leader Fall Pruning Honeylocust Co-dominant Leaders in the landscape are rarely removed Spring planted 1st year Training central leader Removing potential codominant leaders in nursery. Removing potential codominant leaders in nursery. Result of failing to remove interior branches Following ice storm It will have to be removed at some time 2nd year Codominant subordination – prune to outside bud result 2 year maple pruning/training result Interior removal of leaves and small branches personal preference. Pruned 2 year old maple Owner/manager mark that pruning work has been checked. Willow Oak Bradford pear and finely branched willow oak following the ice storm both removed other willow oaks able to be kept Remove abnormal growth. Staking Wooden Stakes Bamboo Electric Conduit 10’ Whoops! Fiberglass Poles “Flexing” before staking Pruning Shrubs Hand pruning in a large nursery to train multi-trunk birches Large tree pruning is like landscape pruning On over 4 inch trunk caliper space branches so that branches are not less than 15-18” directly above or below another Large street trees with 13 foot clearance for trucks Landscape pruning http://hort.ifas.ufl.edu/woody/pruning/raising.htm Cut at branch collar Cut too close: inside branch collar Cut too close: inside branch collar Unacceptable flush cut Sometimes storm damage leaves no alternative Hazardous dieback stump when cut is made without foliar support Have a planting plan for replace old existing plants The best way to avoid routine pruning maintenance is to place the right plant in the right place. Winston Dunwell http://www.ca.uky.edu/HLA/Dunwell/win1.html