How to Prune Ornamental Shrubs
For ornamentals in Zone 4-5
Guiding Principles of Plant Friendly Pruning
- Prune to enhance a plant’s natural beauty
- To make it feel less oppressive, tidier, cleaner
- To reduce size somewhat, depending on the type of plant.
- Selective pruning will reduce the bulk of the plant and taking off a fewer lower limbs of a tree is okay
- Prune to maintain plant health, vigor and longevity
- Remove dead/diseased parts
- Remove limbs that will rub and cause a wound to let disease and insects in.
- Remove sucker type growth as it weakens the overall tree structure and impedes vigor
- Prune to remove hazards
- Blocking line of site for vehicular traffic
- Weakened limbs that would be prone to fall in a storm
Major Pruning Mistakes
- Ornamental trees should never, ever be topped, meaning the top cut off.
- Shrubs should very rarely be sheared (except real topiary and formal hedges).
- Stripping all of the side branches off of a mature pine or any other tree or shrub, is also not acceptable. Stripping is not to be confused with selective thinning, which can also make shrubs and trees look open and Oriental.
How to Prune so Your Plants Don’t Look Like They Just Lost a Bet
You need to know about 2 types of pruning cuts.
Thinning and Heading
There are two types of pruning cuts, thinning and heading.
Heading - Use heading to create a bushier plant. A heading cut is pretty much just cutting off the tip or end of a branch, twig, or stem.
The next spring growth is stimulated at the tips of cut branches. Shearing, topping and pinching hedges are heading cuts. Good for hedges and chrysanthemums. Not too good for most shrubs and trees.
Thinning - Use thinning to lighten up or remove density from a plant.
A thinning cut removes the branch back to another branch or twig, or to the ground. Most pruning consists of thinning cuts. It forces new growth in existing branches and spreads new growth more evenly throughout the plant. Thinning cuts will let light inside, allowing for green growth inside and not just dead looking twigs. It also means that if you need to reduce the size of the plant at some point, you would still have a plant that looks reasonable. You would have branches to cut to if you choose to reduce the size.. It also stays “neat” longer and looks natural.
Pruning by Habit
The Three Growing Habits of Plants.
Prune to enhance the plant’s natural shape or “habit”. Plants have one of three basic habits.
- Cane Growers
- Plants that renew themselves by sending up new branches – called canes – from the base.
- They are generally tough plants.
- Spireas, forsythias, roses, bamboo, kerria, weigela are all very hardy plants in this category.
How to prune a cane-growth habit plant.
- Take a good, hard, long look at your shrub.
- Envision what it should look like.
- Consider what is your desired result?
- Hold that in your mind throughout.
- After each planned series of cuts, stand back and re-evaluate.
- Take out all dead, disease or dangerous wood. Always do this first.
- Plan to take out about 1/8 to 1/3 of the plant
- Start with the biggest and oldest, as well as a few of the weakest canes.
- Remove the whole branch all the way to the bottom or base of the plant.
- Do this every year to keep the size controlled.
- Pick out a few of the worst canes that rub or cross each other, that look sick or go the wrong way (that is, start at the outside, head back through the center and out the other side)
- Remove ugly branches (usually too straight).
- Generally prune to:
- Open up the center.
- Tidy up the top with thinning cuts.
- Cut back anything hanging on the ground
- Leave a growing point. Meaning cut a short distance about a twig, branch or node. Cut to a side branch or bud.
- The plants look like mounds and are medium-tough plants.
- Found in mass planting.
- They have small leaves and supple branches. In general, yur goal is to neaten them up or make them smaller. These poor things are the usual victims of those who want to just cut them into balls with hedge shears and be done with it. Ouch! People like to shear them --- please don’t be one of these perpertrators.! Examples of mounds are abelias, escallonia, barberries and Mexican orange. These are easiest to make and keep small so there is no excuse for the bad haircut.
How to prune a mound habit plant.
- Locate the longest, most unruly branch.
- Grab the tip with your left hand.
- Follow the branch down
into the interior of the plant with your right-hand pruners, and snip it off two inches to one foot below the general surface level (TOP) of your shrub.
- Cut to a side branch or bud, if possible. (Grab & Snip method)
- Do this all over your shrub until it looks miraculously tidy and shorter, but natural.
- These shrubs often benefit from taking out some of the old canes at their base. This opens up and renews the shrub.
- Any dead wood or weeds should also be removed.
- Best left to get big.
- These shrubs are the hardest to do and should not be overly pruned.
- Good selective pruning can open them up and make them look less dense and over powering
- Branches can be trained around gutters/eaves troughs, rather than amputation of limbs. Certainly a more aesthetic approach.
- Tree-like growth habit plants have rather stiff branches, usually. Examples of tree-like growth habit plants are Rhododendrons, Andromeda (pieris), magnolia, deciduous Viburnum, camellia and witch hazel. Most of these plants just need all the dead wood taken out.
How to prune a Tree Like habit plant.
- Never remove more than 1/8 total leaf surface in one year.
- It stresses them or it can cause a watersprout-rebound effect-Yuck
- Just remove any dead or diseased wood.
- If you still want to do more
- Take out suckers (straight-up, skinny branches from the base and trunk of the shrub or tree).
- Take out any big crossing, rubbing branches and double leaders (two main top branches with a narrow branch-crotch angle) on trees.
- Take back or remove any branches hanging on the ground, if only up ½”.
- Take out the worst of the smaller crossing, rubbing branches, choosing the healthiest and best placed branch to remain.
- Prune to shorten or completely remove the worst wrong-way branches that start from the outside of the shrub, and go the wrong way back into the center and out the other side. Sometimes a side branch of the shrub, and go the wrong way back into the center and out the other side. Sometimes a side branch has a smaller branch that heads too far up into the next “layer”, or goes too far down. You can cut some of these off to add more definition to your shrub’s branches.
- If you have two parallel branches rather close together, it may look better to remove one.
- If you, have three parallel branches you may want to remove the center one. This will make things look nicer.
- Before you finish, stand back and look
- If necessary, you may shorten a few branches on tree like shrubs (not trees). Cut back to a side branch.
Hints and Tips
On many shrubs and trees, especially tree-likes, you want to fix things slowly over three to five years. Do some now, come back next year. “Wander, ponder; and prune,” the old saying goes. Pruners always stare at their shrubs, trying to locate unwanted branches, imagining their shrubs without this or that branch, seeing how it will grow next year --- seeing what needs to be done. Much like a haircut, it’s easy to take it off, hard to put back on. Know when to quit.
If a plant is really too big, you may want to move it, remove it go ahead, be ruthless!) or renovate it (not dealt with here). But try real selective pruning first!
Mounds (Grab & Snip) Spiraeas, Hollys, Escallonia, Japanese Holly, Box Honeysuckle
Cane Growers (Cut canes to the ground) Roses, Oregon Grape, Kerria, Weigela, Wild Oregon Grape, Nandina (Heavenly Bamboo), red-twig Dogwood, Buddleia (Butterfly Bush), Hydrangea, Bamboo, Deutzia, Forsythia
Tree-Likes (Thin-out, many small cuts) Elderberry, Manzanita, Kalmia, Deciduous Azaleas, Pieris (Andromeda), Rhododendrons, Enkianthus, Huckleberries, Lilac, Viburnums (Leatherleaf, Doubl-File, Highbush Cranberry, Winter, Snowball) Spindletrees