Pruning your California Native Plants

It is important to prune and groom your California Native Plants.  This guide will help you asses the proper technique to prune your trees, shrubs, vines, perennials, and grasses.  

Before you practice these techniques and methods you should decide what you would like to change about the plant.  Why are you pruning it?  Do you want to remove dead branches, control it’s size, make it the focal point in your garden, prune it because it has become too leggy, or match it to your preferred garden style? You will not be able to achieve your desired plant instantly, it will take time from a few seasons to years.  You should create pruning plans- what do you want to achieve in one year, two years, three years, etc.

Pruning most shrubs to limit their size will not work.  Once you prune plants they grow fast to compensate for their loss of foliage.  If pruned often to maintain size they will lose their vigor and grow to have a twiggy exterior.  It is recommended to choose an appropriate size plant for the space.  When plants do need to be pruned it is not a great strategy to prune it back to the size you would like it to be.  Locate the branch that is growing too tall and trim it where it meets a major branch.  The plant will have a hole for a period but will fill that hole in.  

You should plan to prune when a plant is dormant or when the plant is about to grow new growth.  Pruning weakens a plant because the leaves are removed which is a form of food source for the plant.  Pruning also creates wounds that the plant needs to heal.  Healing tissue will cover the wounds with new growth helping the plant recover quickly.  The new growth will assist in hiding the pruning cuts.  

To help the tree heal from pruning wounds you need to preserve the branch collar.  There is a swollen band of tissue at the base of every branch that will grow over the wound after the cut.  Always cut beyond the edge of the branch collar when you make a thinning cut.  When you are making a thinning cut you should follow the one third rule.  The stem should be at least one third the diameter of the one you want to remove.  A stump will not heal if pruned beyond the collar.

Only prune a maximum 20% of a trees canopy at a time.  Deciduous trees should be pruned in the winter, this way you can evaluate the structure without the leaves.  Pruning a deciduous tree in the summer while they have leaves will cause the trees to have a dwarfing effect.  It is not recommended to remove large branches, just a little of the current season’s growth.  You can practice this on the California buckeye (Aesculus californica), spice bush (Calycanthus occidentalis), Western redbud (Cercis Occidentalis), ash (Fraxinus spp.), California sycamore (Plantanus racemose), cottonwood (Populus spp.), Oaks (Quercus spp.), Willow (Salix spp.), and Mexican elderberry (Sambucus Mexicana).  Maple trees (Acer spp.) will bleed excessive sap if pruned with this method.

Below is a list of different ways to prune your natives.  Most product pages will list when to prune your plant.

When you want to create a longer blooming season, rejuvenate the plant, or spruce up the appearance of your plant you should dead head the flower stalks and seed heads.  Dead heading is when you remove dead or spent flowers or flower clusters after the plant stops producing flowers.  You must dead head flowers before the plant produces seeds.  Dead heading is beneficial to the plant because you are preventing the plant from going to seed, thus  producing  more energy to produce new growth.  You should dead head flowering perennials, annuals, and non woody plants- they will produce more flowers.  Trees and shrubs will not flower again, they need to rest or go dormant before they can produce more flowers.  Plants that flower up the stem, such as Monkey Flowers respond to removing each individual dead flower.  You can also remove the entire stem and the stem will grow back.  This method should be practiced on native perennials at the end of their blooming cycle or in early fall.  

 Dead heading a spent flower.      The spent flower turned into a seed pod.

Removing the tips of stems is called Pinching or Tipping.  You should pinch or tip young plants and perennials.  Tip pruning shortens an elongated twig that is less than an inch in length and a quarter inch in diameter.  This method is used when you want to reduce a plants canopy.  This is the least aggressive cut to a plant within the other methods.  It is not recommended to remove tiny flower buds and stems.  You should pinch or tip the plant two times a year, when you see rapid growth and when flowering is finished.  Woody natives respond well to tipping cuts because they grow new growth just below the cut.  

Thinning is the process where you remove the entire stem and branches to allow more light and room for the plant to grow.  You should make the cut at the base of the plant.  This is the most effective method to show the natural habit of a woody plant.  This is also helpful to accentuate the plants growth habit.  All plants grow up and out, thinning aids in achieving this growth pattern.  You can thin all plants.  

If you want to prune plants or ground covers along paths, streets, between lawns, and plants next to planter walls you can edge the plants.  Edging is thinning back the longest stems to the main body of the plant.  You can edge yarrow, strawberries, Bee’s Bliss, Dana Point buckwheat, and Yankee Point ceanothus.  When you are edging be careful not to cut all of the branches back to the same point.  If you do cut all the branches to the same point the plant might produce a layer of live growth on the top and dead growth on the bottom because the branch will grow new stems that pile up over time.  

Heading back is when you cut back all the stems of a plant.  You can lightly head back a plant by pruning the tips of each stem.  Hard head back is when you prune the stems back to the base of the plant.  Most natives appreciate a light heading back.  A new stem and branch will grow where you pruned it.

If you want your tree or shrub to look like a formal hedge you can shear or hedge it.  The California Natives that will not respond to this method are: Chamise, Howard McMinn Manzanita, Sunset Manzanita, Coyote Bush, Yankee Point Ceanothus, Pacific Wax Myrtle, Hollyleaf Cherry, California Coffeeberry, Scrub Oak, Spiny Redberry, Lemonadeberry, California Grape, and Desert Grape.  You should shear your plant two to three times a year and when your plant is putting out new growth.  Hedges are wider at the bottom and narrower at the top.  If you hedge the plant to be wider on the top the plant will not receive enough light and branches will die.  It is not possible to start dense growth at the base of a hedge from old growth.  Shearing is a bunch of tipping cuts.

Pollarding is when you prune back all of the shoots to the same point each year.  This process is typically practiced on deciduous trees and is a skilled pruning.  You should only do this to the California Sycamore and Velvet Ash.  The tree will produce abnormal thickened branches after pollarding.  

Coppicing is when you cut back a woody plant or tree to the ground, less than 6” high.  You should do this when you want to invigorate an older plant or if you want the plant to produce upright shoots.  Western Redbuds, American Dogwoods, Chamise, Cottonwoods, and Jojobas will respond well to coppicing.  

You can move or brush mow shrubs and grasses that will tolerate it.  Mowing with a lawn mower or brush mower is used to cut plants down to the ground.  You can mow Fescues one to two times a year.  Blue grama can be mowed once a month up to three inches tall during the warmer seasons.  You can mow Coyote Bush and Poverty weed in the winter if they get too tall or bulky.  It is recommended to lightly fertilize with a nitrogen fertilizer to help them recover after mowing.

Corrective pruning is helpful for larger trees and shrubs that have structural problems.  

Proper tools for pruning

Bypass pruners- a sharp blade cuts the stem.  Pruners can be sharpened when they become dull.  You should never try and use a pruner for a branch that is larger than one inch in diameter.  

Handsaw for larger cuts.  The teeth design should be cut on the pull rather than in both directions.  Replaceable blade saws are preferred.

Ensure your tools are always sanitized prior to using them.  They should also be consistently sharp.  Remember the tool should be doing the cutting, not you!  

To sharpen your tools we recommend a diamond file or stone.  To use a file to sharpen a tool you should move the file in one direction across the full length of the beveled edge and maintaining a 15 degree angle.  Tools should be oiled and cleaned after each use to avoid rust.  Diseases can be spread from plant to plant if the tools are not sanitized after each use on a single plant.  To sanitize your tools you can wipe them with alcohol before and after each use and after every cut.