A mysterious disease has botanists on red alert after a tree in the Presidio started oozing fluid.
It's called "sudden oak death," and it's plagued the region's trees for years. This is the first time it's been identified in the national park, although it's popped up in the past around Golden Gate Park.
Nobody's sure how the disease made it into the Presidio. Rainy weather can cause it to spread, but it wasn't the recent precipitation that caused this particular case: the tree has been sick since October, according to the Ex.
The likeliest vector is a non-native plant in someone's garden outside of the Presidio. It's a poignant reminder that cultivating invasive species is risky business, and that native plants are preferable to those brought in from outside San Francisco's unique Mediterranean coastal climate.
As the restoration of the Presidio continues, planners are taking steps to make sure that incoming plants are appropriate for the setting. Several years ago, the park planted a hundred Monterey cypress and pine trees which were bred for resistance to Pine Pitch Canker fungus.