Anza-Borrego Desert State Park. At more than 600,000 acres, this is the largest state park in California. There are 500 miles of dirt roads and countless trails for hiking. Visits here are especially popular during the two-week desert wildflower bloom, which happens between early February and late April. The exact timing depends on winter rains, so it's best to call the park ahead for advice. The park is about a two-hour drive east of downtown San Diego, at the far eastern end of San Diego County. 200 Palm Canyon Dr., Borrego Springs, CA, 92004. 760/767–4205. www.parks.ca.gov.
Carlsbad Flower Fields. This commercial nursery that's also a tourist destination is for anyone who wants to see a seemingly endless sea of red, yellow, purple, and pink blooms against the distant blue sea. The fields are only open to visitors when flowers are in bloom from March to May. Don't plan a trip in any other season or you'll just see a field of dirt. In spring, drivers on I–5 can steal a peek at the ranunculus fields, which burst with lively color. 5704 Paseo Del Norte, Carlsbad, CA, 92008. Exit I–5 at Palomar Airport Rd. and head east; turn left at Paseo Del Norte then right into parking lot. 760/431–0352. www.theflowerfields.com. $12.
San Dieguito River Park. This 55-mile corridor begins at the mouth of the San Dieguito River in Del Mar and heads from the riparian lagoon area through coastal sage scrub and mountain terrain to end in the desert, which is east of Volcan Mountain near Julian. It's open to hikers, bikers, and horses. The expansive park is also home to the Sikes Adobe Farmhouse, an 1880s farmstead that was almost completely destroyed by wildfire in 2007. After painstaking restoration it reopened in 2010 and is now home to a museum. The restored adobe creamery reopened in 2014. 18372 Sycamore Creek Rd., Escondido, CA, 92025. 858/674–2270. www.sdrp.org.
Tijuana Estuary. Mostly contained within Border Field State Park, this estuary is one of the last riparian environments in Southern California. The freshwater and saltwater marshes shelter migrant and resident waterfowl. Horse-riding trails fringe the south end of the Tijuana Estuary in Border Field State Park. The visitor center is open Wednesday through Sunday, but the trails are open daily. 301 Caspian Way, Imperial Beach, CA, 91932. Exit I–5 at Coronado Ave., head west to 3rd St., turn left onto Caspian, which leads into estuary parking lot. 619/575–3613. www.tijuanaestuary.com.