Pruning Landscape Plants

Trees and Woody Shrubs

Proper pruning helps a tree become strong, healthy and attractive.  Consequences of not pruning include development of low limbs; accumulation of dead branches; weak, codominant stems and included bark that can lead to increased risk of breakage.  Its important to know why youre pruning, what youre pruning, and how to prune it before even starting.  Seven objectives of pruning are:

Reduce the risk of failure
Provide clearance
Reduce shade and wind resistance
Maintain health
Influence flower or fruit production
Improve a view
Improve aesthetics

A tree can be properly trained while its young (ages 3-5 years) by performing these five steps:

1. Remove broken, diseased, dying or dead branches
2. Select a leader and remove competing leaders.  The strongest and most vertical stem can be selected.
3. Select the lowest permanent branch.  The lowest branch for street trees would need to be 8 feet over the sidewalk and 14 feet over the street for minimum clearance.  Look for a vigorous branch with a strong attachment.
4. Select scaffold branches and cut back and remove competing branches.  Scaffold branches are the permanent branches of the tree and constitute its framework.
5. Select temporary branches below the lowest permanent branch.  Remove branches below the lowest permanent branch with a diameter of greater than 1/3 the diameter of the trunk at the point of attachment.  Smaller temporary branches along the trunk should be left for a year or two but can be pruned back to one or two buds.

Pruning Mature Trees:

Trees that have been properly trained when young require minimal pruning as they mature:

Remove dying, diseased or injured wood.
Remove crossing or crowded branches.
Reduction cuts can reduce the height of a tree in a healthful, appropriate way, and they can also reduce the weight off the end of a heavy branch to help prevent it from breaking.

NEVER top trees.  Make thinning cuts rather than topping cuts.  Topping is the indiscriminate removal of branches with no thought or reason behind it other than to cut off the branch.  Topping allows all the buds below the cut to break so water sprouts develop which creates poorly attached branches that need to be pruned every year to avoid having them break off the tree.  Topping leaves open wounds for insects and diseases to enter, and it ruins the natural shape of the tree.  Use thinning cuts that remove a branch back to another branch that is at least 30-50% as large as the branch being removed.

Generally no more than 25-30% of a trees foliage should be removed in one growing season, and often this is more than needs to be removed.  Its especially important to leave small branches along the entire length of a larger branch.  Removing all the small branches can lead to “lions tailing”, which is structurally unsound.

Its very helpful to observe a plants growth pattern over the growing season. Learning to recognize “growth buds” will help identify where to make cuts.  In general, removing a terminal bud (at the tip of a branch or shoot) forces the branch to develop in the direction of other growth buds. Consult a reference book on garden pruning (Sunsets Western Garden Book is an excellent source) for more information about how and when to prune plants in your garden.

Deciduous and broad-leaved evergreen trees can be pruned in winter after the leaves fall so that the structure of the tree is more apparent.  However, trees can also be pruned during the growing season to remove diseased or insect-infested wood (for example, shoots killed by fire blight), to direct growth, to remove growth that obstructs signs or windows, or to control water sprouts or suckers.  In some cases, pruning during the growing season should be avoided entirely for pest management reasons (for example, to avoid attracting bark beetles).

Do not use sealer after pruning.  The tree will compartmentalize the wound on its own.

Consult a reference book on garden pruning for more information about how and when to prune plants in your garden. Excellent sources are:

Sunsets Western Garden Book

An Illustrated Guide to Pruning by Edward F. Gilman.

RHS Pruning and Training by Christopher Brickell and David Joyce


Tree Care references

LandscapeTree Care

Trees and Utilities (PDF)

Trees are Good

Shrubs and Non-woody plants:


Shrubs: Prune young shrubs just enough to develop strong, shapely forms. Prune flowering shrubs to produce more blossoms. Prune older shrubs to remove unhealthy or unwanted branches.


Flowering shrubs: In general, prune after flowering (spring or summer), depending on bloom times. Roses should be pruned in late winter and tender or semi-tropical shrubs in late spring.


Non-woody plants: Many perennials and grasses even herbs and vegetables may benefit from periodic grooming (pinching, deadheading, cutting back).


Repeat-blooming perennials: Shear repeat-blooming perennials, such as lavender, after each bloom. Use hedge shears, scissors, or sheep shears. Do the same for loose-stemmed flowers, such as alyssum, to induce a fresh round of blooms in midseason.


Long-blooming perennials: Deadhead long-blooming perennials, such as daylilies, coreopsis, and geraniums by snipping off the spent flowers with shears. The result will be a longer bloom.


Foxglove: For a repeat show, cut faded stalks down to 4-6 inches.


Iris: Divide overgrown iris clumps by digging out their shallow rhizomes in the fall. Snap or cut them apart at their joints and discard any rhizomes that do not have a fan of leaves.


Multi-stemmed perennials:  To create more plants from multiple-stemmed perennials such as red-hot pokers, dig up the entire root ball and split it with a sharp shovel or fork. Take sections that contain both roots and green stems, trim the stems to 4-6 inches, and replant.


Grasses and Ferns: Cut off browned or damaged leaves near the center of grasses and ferns when you see new growth in spring. Comb your fingers (wear garden gloves) through foliage of ornamental grasses to remove old leaves. Cut back ornamental grasses, salvias, lavender, and deciduous perennials to 4-6 inches above the ground to make room for new growth. Do this job in late winter when dead plant parts can easily be pulled from the ground.


Flowering hedges:  Lightly trim flowering hedges early in the year forsythia, for example immediately after flowering by cutting out all, or a portion of, the old, flowering wood. Flowering hedges are generally more effective and flower more abundantly if they are allowed growth before they are pruned.


Large, leathery leaf plants:  Plants that have large, leathery leaves, such as Catalina cherry, or strong heavy stems, such as certain types of roses, should be pruned with a sharp knife for a neat cut. Shears and trimmers destroy the appearance and integrity of the leaf shape, causing the damaged leaves to turn brown before they fall.