A large seed bank of weed seeds is almost certain to exist and weed suppression for several years may be needed. Spot weeding may be needed for the first year or two. Competition from fast growing exotic weeds may not kill native shrubs but it does reduce growth. Consider using a blanket wiper, wick, mow or graze weeds. Late spring burns will help where they can be done safely, burn before seed maturity on weeds.
Irrigation is needed in most years.
Hand-water into treeshelters or install deep pipes or vertical porous hose. The Dry-water additive has not been successful in most cases. Overhead watering can encourage weeds and be detrimental to native species, but may be successful if timed to mimic natural rain events. Conclusion Coastal sage scrub can be improved and restored on almost any site if functional repairs to site hydrology and soil chemistry and structure are made. Many of the plants are vigorous and grow rapidly with water.