As the lure of the rebate attracts you, understand that March is a bit late in the year to be putting in a new garden in Southern California. Yes it can be done, but your tender young plants will have an especially tough time making it through their first hot, dry summer and fall. If it is possible I would suggest ridding your lot of its green cover (taking care to protect existing mature trees) and planting enough plants to meet the rebate requirements but hold off on as many of the woody shrubs and trees as you possibly can. Instead, clear the grass, install irrigation (if you plan to have an automated system) and hardscape (paths, benches, steps, etc.), lay down mulch, and plant some native bunchgrasses and other herbaceous perennials.
You may be wondering why it is difficult for native plants to survive a spring or summer planting, especially if your landscaper seems to have no problem planting at any time of the year. California native plants that are adapted to our long hot and dry season have interesting strategies for survival. They usually slow down and go dormant during this time of the year. Even with supplemental water, they prefer to stop growing. However, with our high temperatures and low humidity, they will have a very hard time getting through the dry season. Some will succumb to excessive wilting, being unable to keep up with water loss, while others will be subjected to disease-causing microorganisms that multiple in warm, moist soil. Planting in late fall or winter gives them a bit more time to start to become established before the extreme heat arrives.
|Catalina perfume (Ribes viburnifolium) planted in shade of
coast live oak on March 6, 2011 did fine with very little
supplemental water, even in summer.
I have planted during most months of the year and my experience is that I usually have high losses with spring planting, and rarely succeed at all in summer. As mentioned above, grasses, especially warm season growers, like deergrass and alkali dropseed, usually do fine. Plants grown in shade do better than those subjected to relentless sun and heat. However, desert plants often do all right with summer planting because they are adapted to summer, monsoonal rains. Finally, native plants that grow year-round in moist conditions may survive since they are adapted to warm, moist soils and usually are less susceptible to the root rot that is so harmful to many summer-dry plants.
If you must plant in spring, the following practices may improve your success:
- Avoid chaparral and coastal sage scrub shrubs that are adapted to hot, dry summers. Instead plant grasses, perennials, and desert and riparian plants (those adapted to year-round water). Wait until the following late fall to winter to plant specimens adapted to summer-dry conditions.
- Mulch plants to help moderate soil temperature and reduce water loss. Be sure to keep the mulch a few inches away from plant stems.
- Grow annuals like sunflowers to provide protection and shade in summer for your new perennials.
- Water carefully! You must observe each plant and check the soil in and around the rootball to determine when to water. Be sure to water thoroughly and then allow the plant to become moderately dry, avoiding severe drought-stress.
- Screen wilting plants from the sun with a chair or even a white sheet. This can help young plants survive our all-to-frequent, triple-digit heat waves.
|Vegetable garden under sheet during
heatwave on June 30, 2013.
- Gently feel around the rootball of new plants that are wilting often. The organic material in potting mix that surrounds the rootball can decompose quickly in the heat, leaving large air pockets. The roots dry out quickly and will do much better if you carefully press new soil into these pockets. Then water thoroughly. I have saved many plants with this simple practice.
|Most of these Margarita BOP penstemons (Penstemon heterophyllus ‘Margarita BOP’) did fine following
planting in early February 2013.