HELLO, DAHLIA / CALIFORNIA’S LATE BLOOMER

Daly City Dahlias, flowering at the far left and far right, bring a late-season burst of color to a residential San Francisco garden. New York Times.

When most summer flowers begin packing it in, dahlias are just getting started. These spectacular late bloomers generally reach their peak in August and September and may continue flowering well into fall. 

Native to the highlands of Mexico and Central America, dahlias developed on a seasonal timetable influenced by late-summer rains, shortening days and cooler nights. That inherited rhythm helps explain why they come into their glory just as many annuals are fading. 

 California suits dahlias particularly well. Much of the state offers abundant sunshine, comparatively mild nights and a long growing season. Coastal areas provide another advantage: Dahlias prefer moderate temperatures and may struggle when prolonged heat rises above 90 degrees. 

They also flourish in loose, well-drained soil with regular deep watering. California’s mild winters allow their underground tubers to remain in the ground in many areas rather than being dug up and stored against a hard freeze. San Francisco’s cool, fog-tempered summers are especially agreeable to the flowers. 

Dahlias have long been grown in the city’s western residential neighborhoods, including the Sunset and Richmond districts. They need six to eight hours of sun, however, so gardeners must choose their patches carefully. Regular deadheading encourages the plants to keep producing flowers into fall. 

UC Master Gardeners recommends well-drained soil, modest watering when tubers are first planted and avoiding nitrogen-heavy fertilizer, which produces foliage at the expense of flowers. 

One of San Francisco's most impressive displays (above) can be found at Sisterhood Gardens, a community garden at 116 Arch Street, at the corner of Arch Street and Brotherhood Way, in San Francisco’s OMI neighborhood. 

Established in 2016, the garden maintains an unusually diverse collection of locally bred dahlias. Sisterhood Gardens For gardeners, that late arrival is part of the dahlia’s charm. It does not compete with spring’s grand entrance. It waits until the garden needs an encore—and then steals the show.