For better or worse, eucalyptus trees from Australia have become a major component of San Diego's contemporary "urban forest." More than a century ago, in locales such as the UCSD campus, Rancho Santa Fe, Scripps Ranch, and coastal North County, tall varieties of eucalyptus were planted in a misguided effort to produce wood for railroad ties. These trees largely escaped the ax after it was discovered that eucalyptus wood cracks and splits too easily for use as lumber. Eucalyptus trees young and old still drape some hillsides just east of Interstate 5, and above Buena Vista Lagoon in Carlsbad, at a place called Hosp Grove.

The city of Carlsbad maintains a small nature park and trail system within Hosp Grove. Sunny days in fall and early winter are perfect for enjoying this little patch of serenity in an otherwise busy corner of North County. To get there, exit Interstate 5 at Las Flores Drive in Carlsbad. Go west on Las Flores a short distance, then turn right on Jefferson Street. Proceed 0.6 mile to Hosp Grove Park on the right, opposite Buena Vista Lagoon.

The Hosp Grove Trail rises on the slope behind the park. If you turn right, heading west toward a dead-end, you'll quickly get an eagle-eye view of Buena Vista Lagoon, which is especially effective because you peer over the tall obscuring vegetation on the shoreline. Bring along binoculars -- or better yet a spotting telescope -- to scope out the bird life below.

The main Hosp Grove Trail goes left, contouring southeast, quite high along a steep slope, right through the eucalyptus forest. Not much grows here other than eucalyptus, since the leaf litter from these trees poisons nearly every other type of plant. Eucalyptus branches, though, are attractive to monarch butterflies, which arrive at Hosp Grove and about two dozen other sites around San Diego County around November to spend the winter season in relative warmth. The butterflies migrate from their summer homes in the Sierra Nevada and the Rocky Mountains, navigating to coastal California and Mexico by unknown means.

After less than half a mile, the main Hosp Grove Trail descends, turns sharply left, and returns to Hosp Grove Park alongside city streets: first Monroe Street, then Marron Road. Just east of here, across Monroe Street, additional trails meander amid the eucalyptus trees overlooking the Westfield Plaza Camino Real shopping center.