Descanso Gardens has notable collections of roses, camellias and wonderful nature trails.
Huntington Gardens has excellent collections of roses, particularly of English Roses, a world renowned succulent collection, camellias, a slope of subtropical shrubs, and a growing Australian plant collection in addition to their library and museum.
Quail Botanical Gardens has a wide variety of plant sections. Notable collections include Pacific tropical plants, bamboos, and an interactive children's garden.
Rancho Santa Ana Botanic Gardens is noted for its native California plant hybridizing and extensive collections and trails.
Ruth Bancroft Garden has taken the drought tolerant garden and presented it in a way that is both stunningly beautiful and educational.
Santa Barbara Botanic Gardens is noted for its gardens with California Native plants grouped by plant community.
UC Berkeley Botanic Garden has an excellent collection of interesting and unusual plants. Many have still not made it into the trade. It is well worth the visit.
UC Irvine Arboretum has an excellent South African plant collection but are probably most noted for their bulb collection.
UCLA Mildred Mathias Garden has a number of experimental beds. They have worked on a number of succulent selections, monkey flower selections and many other plants that have become mainstays of the landscape trade.
Pest Species List: It is important not to release problem plants into the wild. This group at UC Davis tracks plants that are becoming problems. Responsible nurseries, at the very least, should not sell plants that are known to be problems in the areas where there are already expensive eradication projects funded.
Invasive Plants to Avoid: and a list of nurseries that have agreed not to sell them.
UC Integrated Pest Management has information on the latest beneficial insect species. Biological solutions are being worked on for the Giant Whitefly, the Lerp Psyllid, and the Glassy Winged Sharpshooter. The Giant Whitefly is a problem for hibiscus and a number of other large leaved plants. The plants look as if they were growing a white beard. The Lerp Psyllid is defoliating the red gum eucalyptus. It looks like a small cream colored cap. The Glassy Winged Sharpshooter has gotten most of the press. While it causes some damage to plants in the garden it has the vintners in a panic. If you walk under a tree where it looks like it is raining while the sun is shining this is the likely culprit. They look like a 3/4" long cigar.
Crabs and Crustaceans are suffering from our garden runoff. Several problems found in the Eastern Seaboard fisheries are being linked to excessive nitrogen in runoff waters. These pollutants are directly linked to the destruction of the menhaden and blue crab fisheries. We have similar issues on the West Coast with nitrates and pesticides creeping into our groundwater, and pesticide and bacteria laced water flowing into the ocean from our coastal communities. We can improve this problem one yard at a time by thinking of organic means of tending our small plots of land.