California Botanic Garden
Formally known as Rancho Santa Ana Botanic Garden, this is the largest garden dedicated to native California plants. The 86-acre garden has a few educational programs such as a grad degree in botany through Claremont Graduate University. Check out the website for updated free days. Otherwise admission is $10 for adults, a little less for seniors and kids. Hours are 8 AM to 5 PM daily except major holidays.