Pruning can be an intimidating garden task for some people. But, by following a few simple rules, you can easily tackle all your pruning projects.
Why do we Prune?
Pruning is done to maintain a shrubs size, improve flowering, fruiting, or bark color, and to remove damaged or diseased branches
First, determine what time of year to prune:
- Spring-flowering shrubs (Lilac, Forsythia): prune right after flowering.
- Summer-flowering shrubs (Potentilla, Spirea): prune when dormant.
- Damaged or diseased branches: remove when they are found.
Next, determine what type of pruning is needed
Some shrubs, like Lilacs, benefit from regular pruning and other, like Barberries, require little pruning. For pruning information, check the plant tag or call any of our garden centers. Some common types of pruning are:
- Thinning: reduce the size and density of a shrub by pruning some of the branches where they join the main trunk. Thinning improves flowering, fruiting, and bark color. It can also reduce some disease problems.
- Heading cuts: reduce the height and spread of a shrub. Prune branches back to a shorter side shoot or above a healthy bud. Vary your cuts to maintain a natural appearance.
- Renewal: used to manage over grown shrubs and to promote new growth. Remove 1/3 of the older branches at ground level and reduce the height of the remaining stems by 1/3 if necessary. Continue to remove older branches each year as needed.
November – February Prune winter damaged branches as necessary.
February – March Prune summer and fall blooming shrubs until new growth appears.
March – May Wait to prune spring-flowering shrubs until after they bloom. Finish by June.
July – Lightly shear Spireas to remove faded flowers and encourage re-bloom; repeat for a third bloom.
August – October Avoid late season pruning, especially of evergreens, which can lead to winter damage from sun and wind.
Evergreens: can require special attention when pruning to avoid damage to the plant.
Pines: grow from the stem tips each year. To control growth, remove 1/2 – 2/3 of the buds (candles) in the spring. More severe pruning can kill the branch.
Spruce: prune in the spring by cutting the stem tips back to a healthy bud.
Arborvitae & Yew: tolerates more severe pruning than Pine or Spruce. Prune in spring before new growth or in early summer after the growth has expanded. Prune branches back to a bud or side branch. Or, for a hedge, shear plants keeping them wider on the bottom. This allows light to reach all parts of the plant.
Juniper: require little pruning when varieties are carefully selected for the space they will be growing in. Remove selected branches in the spring and early summer.
Removing Invasive Shrubs
Sometimes, keeping shrubs healthy may require removing invasive shrubs that can crowd them. In Minnesota, one of the most common invasive shrubs is Buckthorn.
Buckthorn can be identified by a small thorn on the end of the branches. They may have clusters of small, black berries and usually leaf out earlier than other plants in the spring and hold their leaves longer in the fall. To remove, cut large plants back to the ground and treat stump with a total vegetation killer like Roundup. Small plants can be killed by applying a herbicide 12”-15” along the stem. Read all herbicide directions carefully.