Laurie McGonagill, UC Master Gardener of Placer County 
From The Curious Gardener, Winter 2020

The saying that pruning is an art as well as a science is especially true when applied to California native plants. The natural form of shrubs and trees, subshrubs, and herbaceous perennials really shines when care is taken to reveal beauty through careful and limited trimming at the proper time. Native plants do not respond well to constant shaping, as in topiary, or shearing to control size which are common practices with plants in our domestic landscape. They do like a light prune or trim especially if they look shaggy or leggy or to improve their health. But you can also leave them alone to reveal their natural shape.

Unlike many non-natives that dot our landscape which have one dormant period, our native plants have two, summer and mid-winter. These are the most beneficial times to prune. Pruning in late fall or early winter will start new growth that does not have time to harden before it gets cold. Valuable pollinator food and habitat is also removed so it is best not to prune then. Mid to late winter is preferable, although in summer you can remove the stalks of herbaceous perennials to encourage a second bloom.

A few rules apply to pruning plants in general:

•     Remove dead or diseased growth anytime unless the plant is frost-sensitive.

•     Remove limbs that cross.

•     Prune to create air flow and improve light penetration.

•     Prune young shrubs and trees to promote good branch structure.

•     Avoid pruning during wet weather to reduce the chance of infection.

Now, for California natives! Here is when to prune, types of plants to prune, and techniques to use.

1. Prune these evergreen shrubs and trees after they finish flowering: Ceanothus spp. (California lilac), Frangula californica (coffeeberry), Cercocarpus betuloides (mountain mahogany), Arctostaphylos spp. (manzanita). Use a light hand with manzanita as there is no regrowth at a limb that is removed.

2. Prune broadleaf evergreen shrubs and trees in late summer: Quercus spp. (oak), Arbutus menziesii (madrone), Umbellularia californica (California bay laurel), Heteromeles arbutifolia (toyon), even though you will get some of the berry growth!

3. Trim grasses such as Muhlenbergia rigens (deer grass) almost to the ground every other year or so in late summer.

4. Cut perennials and subshrubs almost to the ground in late fall or winter: Epilobium canum (California fuchsia), you can mow it! Romneya coulteri (Matilija poppy), Verbena lilacina ‘De La Mina’ (lilac verbena), flower stalks of penstemon, buckwheat, and salvia species. 

5. Prune these deciduous plants in mid to late winter: Aesculus californica (California buckeye), Ribes spp. (currant and gooseberry), Lonicera hispidula (honeysuckle), Philadelphus lewisii (mock orange), Calycanthus occidentalis (Western spice bush), Vitis californica (California grape), Clematis lasianthus (pipestem clematis), Rosa californica (California wild rose). Note: keep as much of the wild rose as possible since the brush and rose hips are important habitat and food for birds and other pollinators. Exception: Prune Cercis occidentalis (Western redbud) after flowering.

6. 6) Cut plants to the ground (coppice) to rejuvenate: Some plants to coppice include Baccharis pilularis (coyote bush), Carpenteria californica (bush anemone), Cercis occidentalis (western redbud). Coppicing acts on the plant as a wildfire would. This technique should be used sparingly on mature plants that have gotten ragged.

Learn by doing and don’t be afraid to experiment!

Remember: Our native plants evolved to adapt to rocky, mineral-laden soil and long periods without rain. They generally don’t need fertilizer, organic amendments and, once established, regular water. When in doubt, mimic nature! 

References

Oquist, Linda. Pruning California Native Plants. Marin Master Gardeners. UCANR. nd. http://marinmg.ucanr.edu/Selecting_Plants/Plant_Showcase/Native_Plants_574/Pruning_California_Native_Plants/

Zane, Nadia. Spring Pruning in the California Native Garden. What’s Growing On – San Joaquin Master Gardeners. UCANR. February 27, 2015. https://www.ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=16896

Levin, Allison. Pruning Native Plants—Part 1. California Native Plant Society. December 1, 2011. https://www.cnps.org/gardening/pruning-native-plants-4033