Here are a couple of suggestions although a little early for our spring.
I recommend:
*University of California, Davis (about 10 miles west of Sacramento)Arboretum
*Annies Annuals Nursery in Richmond, CA is not too far. check out their website!
*Land Regional Park
3800 Land Park Drive, Sacramento
I hear has nice gardens.
Enjoy your visit to Californa.

Here is a link that might be useful: Annies Annuals

Too late to be useful but my most memorable garden visits in the SF, San Jose and Palo Alto area were Filoli Gardens in Woodside, the San Jose Heritage Rose Garden, Sunset Magazine Headquarters and Garden in Menlo Park and the Japanese Hakone Gardens in Saratoga.

Marianne in Sweden

I am also too late, but for anyone else who is planning on visiting San Francisco, you MUST of course see Golden Gate Park. Just walking through the spacious park is fun and interesting, and there are so many things to look at. It's quite a long park, it extends all the way out to the ocean. Near the ocean side, there is the old Windmill that I think was once used to pump out all the water from the area, which used to be a swamp. My grandmother and I frequently visit the Hall of Flowers (the big glass greenhouse in Golden Gate Park), which is inexpensive and they have a lot of carnivorous plants housed in there. Also in GGP is Stowe Lake (which has a cool waterfall) and you can hike up to the top of the hill, or paddle around in boats. And also, you must visit the Arboretum inside GGP.

While in GGP, you should visit the California Academy of Sciences, which has that awesome, amazing living roof. So beautiful, and ingenious. And inside the museum there is this bio dome containing rainforest-type plants.

Across the street from the Academy of Sciences (and next door to the Arboretum and Stowe Lake) is the Japanese Tea Garden, a charming little outdoor garden that imitates old traditional styles from Japan (not quite the same, but it's still very cute). And they do have a tea house there, that is fun to relax in, especially on a rainy day!

Further more, if you visit the city on a Sunday, Golden Gate Park closes down most of its roads to vehicle traffic, so you can bike, roller skate, walk, or even rent a little trolley and meander through the park totally uninhibited. There's a little group in there that gives free swing dance lessons. You can also rent roller blades and bikes for the day.

If you want to take a walk outside you can check out Land's End, a great little hike and lots of native plants to admire on your way. It takes you along the coast, past the old armory forts, through the woods and all the way to the Legion of Honor museum.

I recommend just driving along Highway 1, up and down along the coast. This runs through San Francisco and is called the Great Highway. It's twisty, winding, and the view of the Pacific Ocean is amazing.

If you want to venture outside the city, I highly suggest driving north over the Golden Gate Bridge over to Muir Woods, in the north bay. So beautiful! It's a great day trip activity, maybe plan to have a picnic while you're out there. The woods up in northern california are just unbeatable, and everyone should experience them in their life.

Haha, okay, that's a lot of gardening-related stuff. I know my city quite well, and I promise you there are some really cool, wonderful things to see here.

You can enjoy the trip by visiting attractions of Sacramento like California State Railroad Museum , California State Capitol and Museum ,Sutter's Fort ,California Delta ,Sacramento Zoo,Funderland.

For others who are interested, I second the suggestions above. Add to the list the Ruth Bancroft Garden in Walnut Creek. Lots of interest in succulents these days, and this would be a good place to see them.

Rosefolly