Crest Canyon, an open-space park within the city limits of San Diego, helps insulate woodsy Del Mar from the upscale, bustling sprawl of Carmel Valley to the east. The canyon, rather like a shallow bowl with an upturned lip on three sides, slopes down from Del Mar Heights Road on the south to San Dieguito Lagoon on the north. Spreading across the canyon floor, native sage-scrub and chaparral vegetation mixes with African daisy, ice plant, saltbush, and other hardy plants that were introduced years ago to solve an erosion problem. Young Torrey pines have been planted here as well, joining the handful of century-old pines that thrive higher up on the slopes.

From Racetrack View Road on the north, a dirt road swings uphill onto the canyon's broad, sandy floor, which was graded many years ago in an attempt to solve an erosion problem. About two-thirds of the way up the canyon (0.7 mile), the narrowing path swings left toward Durango Drive on the canyon rim and thereafter stays high, roughly paralleling Durango, until it reaches Del Mar Heights Road. There's plenty of curbside parking on Durango Drive, which is convenient for those taking the Del Mar Heights Road offramp from Interstate 5.

The lingering cool weather has delayed the springtime blossoming of many wild plants in Crest Canyon. Look for blue-flowering ceanothus (wild lilac) and for a native member of the citrus family -- coast spice bush -- now exhibiting small, white flowers and round, reddish fruits.

If you plan to poke around off the beaten trail in Crest Canyon, keep in mind a couple of caveats: The outcrops of sandstone, especially on the east side, are interesting to look at (from afar) but unstable and potentially hazardous. Watch out for rattlesnakes, too, particularly when the weather warms up.