Goodness, our strong tree opinions have landed on SF Curbed.

We’re in favor of any way to improve tree selection for San Francisco.

We had a conversation with our gardener friend, Mike, last weekend about deciduous trees — the beautiful, the useful, the disappointing, and the ugly. It’s autumn, and along our latitude (37 to 38 degrees north), many deciduous trees are starting to change into their stunningly colorful foliage before going dormant for winter. In San Francisco, not so much; our climate is too mild to allow most deciduous trees to put on the show they’re famous for in the Sierra Nevada, Japan, or the Appalachians, all of which share our latitude but not our climate. We have chilly summers and mostly frost-free winters here. Measured as the annual range of average temperatures, our climate’s mildness (but not warmth!) rivals that of Honolulu’s and San Diego’s. Our warmest month, September, isn’t very much warmer than our coldest month, January, and many deciduous trees need greater seasonal extremes.

Some deciduous tree species are lovely exceptions in SF, but for this post, let’s talk about gripes.

One species that’s a bugaboo for us is Pyrus calleryana, the Callery pear. It’s a classic indicator plant for our area, one that performs differently in different microclimates. In the right climate, which is much of the temperate zone of the United States, this species and its many selections, like ‘Bradford’, and ‘Chanticleer’, produce glorious fall color, burst into clouds of bloom in early spring, and grow to become respectable 40-foot trees. At the San Francisco Flower & Garden show last March, held at the San Mateo Event Center, we admired dozens of these trees in their silvery-white exuberance. We have seen the same healthy bloom every spring at a Marin County mall, the Town Center Corte Madera, where the pears also produce equally stunning orange foliage in fall.

Callery pear trees (Pyrus calleryana) in San Mateo, California

Both of these places are within 20 miles of downtown San Francisco, but Callery pears in the city perform poorly. Trees often hold their foliage while simultaneously pushing out insignificant blooms and popping premature leafbuds well into winter (and even spring), rarely coloring to any pleasing shade, rarely going fully dormant until February, if ever. When our neighbors around the Bay Area are thrilling to the March sight of pears in bloom, our SF trees are sputtering and won’t look okay until July. Perhaps 20 percent of SF’s Callery pears perform as hoped — except that even those 20 percent rarely approach the treelike dimensions of their suburban siblings. And, this last summer, we saw many damaged by fireblight. The irony of this post is that at no time of the year do they look better in San Francisco than now: Eventually through June and July they leaf out (even if they barely bloom) and get nice and glossy green.

It’s a testament to the low standards of wind-beleaguered San Francisco gardeners and landscape designers that few people recognize the poor performance of this tree. Drought, lack of heat, wind (plus poor soils!): Our climate is special, and that often means that trees grown for mass distribution, like Callery pears, are not actually suited to our mild winters and chilly, windy summers. It’s not because of where they’re grown (Oregon, or the Central Valley), but because of the tree’s preferences. But they’re available in quantity at a good price, reference books list them as hardy in our climate zone, and thus they get chosen for planting plans. Rumor has it that Callery pears have been chosen for the current reconstruction of Valencia Street between 15th and 19th streets. Sigh.

Our larger gripe is that we’re planting unhappy trees where beautiful, thriving trees could be grown. Unlike, say, the London plane tree, Platanus X hispanica, which (aside from the ‘Yarwood’ selection) trumpets its maladaptation with powdery mildew, rust and anthracnose weeks after leaves develop, Callery pear simply limps and mopes for six months of the year. In the second-densest city in the US, it’s an opportunity cost; mopey trees take the place of thriving trees, and depress the interest in planting more trees.

Perhaps the overarching gripe we have is inattention to place. Not paying attention to the performance of plants in specific microclimates leaves our city with uglier, unhealthier trees whose commonness cannot contribute to the character of this (climatically weird) place.

Another time, we’ll talk about deciduous trees that we love for San Francisco.