The backbone of a California Wildflower Meadow is the grasses and grass-like sedges; they form the foundation that the wildflowers float above. There are many varieties, and you can either use one type or mix them. And these perennial grasses will stay green even after the annual wildflowers have bloomed and gone to seed:
https://www.cnps.org/gardening/california-native-bunchgrasses-5500
Once you’ve selected your grasses and flowers, it’s time to create your garden. Planting a wildflower meadow is fun and easy. The best time to plant wildflower seeds is in the in the Fall after the first rains, and you’ll need to make sure your plants get adequate water if there’s a dry spell. Here are a few more tips to consider:
http://us39.siteground.us/~theodo50/wp-content/uploads/2013/11/Sowing-California-Native-Wildflowers-FINAL.pdf
Need more inspiration? California has a bounty of stunning wildflowers fields that you can visit in Spring and try recreating – om a reduced scale – in your own garden:
http://theodorepayne.org/learn/wildflower-hotline/
One of the most famous destinations to see wildflowers is the Antelope Valley Poppy Reserve:
https://www.parks.ca.gov/?page_id=627