Drought tolerant gardens in general require excellent drainage. Drought tolerant plants are highly susceptible to root rot caused by water logged soils, particularly in warm or hot times of year. Water logged soil is the most common cause of death for drought tolerant plants. They naturally occur in rocky or sandy soils where sharp drainage guarantees water passes quickly over their roots but doesn't oversaturate and kill them.
Excellent Drainage: add up to______ sharp gravel to soil. Either mix in or mulch the surface with 2-3" depth of gravel, rock or other quarried material.
California native plants in general prefer little to no fertility additives to the soil. Mulching with organic materials (leaf-post, woodchip, straw, etc.) is the best amendment for these gardens unless there is a significant alteration in pH that needs to be made (by adding sulfur or oyster shell flour;. a rare necessity.
Food producing gardens on the other hand will benefit greatly from improved soil fertility. Ensuring fuller and healthier harvest.
Improved Fertility: Add [ideally] organic, microbially active compost at recommended amounts to soil surface prior to planting. Till in lightly in top 2 inches.
Other Soil Improvements: Compost tea is an excellent treatment for any new garden. Compost tea is an aerated extract of healthy compost that kickstarts soil's health and ensures newly planted gardens have enough nutrition to establish easily. Compost tea is especially useful in cases of prior or current soil disease or infestation.
Providers: Compost Tea Guy