A few weeks ago I stumbled across a beautiful California native plant garden at a shopping center. Blue green salvias blended effortlessly with cream white buckwheat blooms while patches of purple verbena and orange monkey flower popped in and out between the blades of deer grass.
I went back to the shopping center a few weeks later and found the garden had been heavily pruned back and most of the naturally shaped plants had been sheared into little round poof balls.
Every plant had been grotesquely sheared with the same technique; however, many plant species in the garden required very different pruning practices to maintain optimal plant health. I realized that the everyday gardener or landscaper may not be familiar with the quirks associated with maintaining California native plants. The main issue for the native plants in this garden was the time of year they were pruned, mid- August. Late summer is not an ideal time to prune for many native species. The species at this garden should have been pruned much later in the cooler fall to early winter seasons to reduce transpiration stress. Pruning in the fall to winter is perfect for many species because the weather has cooled, the plants are still dormant and the coming winter rains will initiate a new flush of growth. There are exceptions to the fall pruning rule. Ceanothus, arctostaphylos and cedar varieties prefer summer pruning because the hot dry weather reduces the risk of pathogens that infect these specific species.
Figure 1 shows a purple sage (Salvia leucophylla) on site that was pruned an appropriate amount. About ⅓ of the foliage was cut away which is the standard for most sages (See Figure 3). However, this should have been done in the fall after flowering. Figure 2 is what the Salvia will look like once it has filled and flowered out.
Figure 4 depicts a showy island snapdragon (Gambelia speciosa) that was pruned back too far. This subshrub can tolerate a hard prune in the fall as long as the cuts do not get into the hardwood. Pruning should only take place in new growth that is tender and green in color (See Figure 6). The cuts shown here are deep into the hard wood of this plant, it will be interesting to see if this plant survives the harsh over pruning. Figure 5 is what the island snapdragon looks like with new green growth.
Figure 7 This Purple Cedros Island Verbena (Verbena lilacina ‘De La Mina’) flowering period was cut short- and the stems not cut back enough. ‘De La Mina’ should be pruned in winter because it flowers and provides color all summer long. This plant can tolerate having 1/3 of its foliage pruned back after flowering (See Figure 9). Figure 8 is a ‘De La Mina’ in full summer bloom.
Figure 10 is a bush sunflower (Encelia californica) that was one of the few plants pruned correctly. This species goes summer dormant and can be almost cut to the ground during summer (See Figure 12). This plant is already starting to send out new shoots and leaf out. Figure 11 shows how the shrub will fill out in the next couple months providing big yellow sunflowers in the winter through spring.
Proper pruning is one of the best ways to extend the life of your native plants and keep them looking great. Doing research and asking questions helps ensure your native plants are getting the care they need. Resources such as California Native Plants for the Garden by Carol Bornstein, David Fross and Bart O’Brien and websites such as Calscape.org are great resources to help you answer your plant specific questions. If you are a property manager looking to install or find maintenance for your native garden, contact Heaviland Landscape Management today.