Pruning Do's & Don'ts
By Bob Chapman
Many gardeners set out to prune shrubs and trees with 24-36 inch lopping shears, hedge clippers and hand-held pruning shears having just the vaguest notion of what and how and why they are out in the garden facing a shrub or tree. Here are some suggestions for the novice as well as for the more experienced gardeners about pruning.
- We prune shrubs and trees to conform to a certain form or shape such as hedges, topiaries and bonsai. We use hedge shears for hedges and some topiaries and small pruning shears are used for working on our prized bonsai.
- We prune shrubs, trees and some ground covers to reduce their height by selectively cutting off branches or twigs. We DO NOT top trees to reduce their height.
- We prune dead and diseases branches by selectively severing them from the trunk or larger branches. Cut the dead or diseased portion vertically (straight across) next to the collar. This allows natural healing of the wound created when we severed the branch.
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We prune larger branches using the three-step method with a pruning saw. Using
this fail-safe technique prevents damaging the healthy tissues and promotes
correct healing. 1. Make an undercut about a few inches out from the trunk or
major branch and about one third to one-half the way through. 2. Start a cut
above the undercut and about 2-3 inches further out, thus severing the branch,
letting it drop and leaving the stub. 3. Cut off the short stub vertically just
outside the "collar" on the trunk or branch. The collar is a swollen portion of
the branch right next to the trunk. When a branch is severed correctly the
collar forms a callous and eventually will seal off the entire cut, thus giving
protection to the tree from diseases and entry by insects.
- We DO NOT prune trees by topping them. Topping usually leaves random stubs subject to decaying, weak, sucker-like shoots, not strong enough to support the weight of new growth (leaves, twigs and branches). Trees that have been topped may produce weak crotches that can be dangerous in wind storms or to arborists or tree trimmers years down the road. The exceptions are the trees that are pollarded when they are dormant. Pollarding consists of cutting off new growth to main branches and can be done to only a couple species of trees. The numerous very long shoots produced by pollarding need to be removed each year.
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We prune to increase fruit production. Mid-winter is the time when most
deciduous fruit trees are pruned, some lightly (apples and cherries, for
example) and others heavily (peaches and apricots) to increase the amount of
fruiting wood, thus heavier crops. Long-handled lopping shears are the preferred
pruning tool for this task.
- We prune roses in mild winter climates in late December to late January to keep our roses at the right height or length and to force new shoots that will produce the desired blooms. We actually prune our roses when we remove blossoms for use as cut flowers. The general rule for hybrid tea roses is to cut the stem just above a five-leaflet cluster facing the outside of the plant, forcing new growth and more flowers for you to enjoy.
- We prune to rejuvenate an older shrub, keeping it to size, removing older canes or stems and letting new ones sprout to replace the old ones that we removed. The rejuvenation of many shrubs usually takes up to three years to accomplish (removing a third each year). Some shrubs can have all stems above the crown removed at one time, but make sure that the shrub you are considering rejuvenating has this ability. Some shrubs, such as junipers, cannot send out new growth from older, bare stems as they lack adventitious buds under the bark. Cutting these back may leave you with a barren spot forever, so only cut off junipers where green leaves are present on the branch.
- We prune to remove undesirable growth. Errant branches, branches crossing the center of the plant, shrub or tree, water sprouts (they grow upright from the trunk or branches) and sucker growth (those growing up from the roots).
- We prune to direct growth, opening up the center, allowing light into it and causing new growth. Doing this stops growth in one direction allowing growth to continue in the other.
- We prune off the tips of shoots or branches (often referred to as"pinching") causing the loss of growth-inhibiting hormones produced by the topmost bud (called "apical dominance"). Removing the topmost bud allows buds below to sprout, thus making the plant bushier. This process is also called cutting back or tip pruning (tipping).
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We prune correctly, cutting off twigs, branches or limbs just above a bud where
possible, not leaving snags or cutting off flush with the trunk or main stem.
These "flush cuts" do not heal properly, and can allow diseases and insects to
enter and possibly harm the shrub or tree.
- We prune to remove faded and dead flowers to make our garden look prettier and to encourage plants to produce new flowers or growth. Many refer to this as "deadheading."
- We prune to remove split or broken branches that threaten to fall, possibly hurting someone walking underneath.
- We prune to remove any growth that might obscure the view of traffic going by, thus showing concern for drivers.
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We prune using the correct tools for the task. Most gardeners use only four
basic tools: hedge shears, hand-held pruners, long-handled loppers and a pruning
saw. We use hedge shears selectively, not on every shrub in the yard, but only
on those specifically needing shearing. Hand-held pruners are great for cutting
off small limbs or twigs up to one-half inch thick or roses for the home. There
are two types, the anvil or the by-pass pruners. The blades of the anvil type
pruners must be kept very sharp, lest the tissues of the stem are torn or
crushed against the anvil instead of cutting cleanly. Long-handled pruners or
loppers are used to cut off limbs an inch or so thick. Pruning saws are designed
to cut off the larger limbs and they have specially curved blades that make it
easy to use when sawing. Tree or pole pruners are good for cutting branches up
to one inch thick that are out of reach, but are not needed in most landscapes.
Bob
Chapman is a well-known professional gardener and landscape contractor.
Currently retired, Bob now spends his time contributing many free-lance garden
articles and columns, and is a much sought after lecturer and horticultural
consultant.