As the shelter-in-place order keeps San Franciscans inside their homes, many have taken to home baking to replace trips to the bakery for fresh bread. The craze has taken off so strongly that it's cleared many store shelves of flour and yeast.

An alternative to yeast is sourdough starter, which can be made at home but usually takes a couple of weeks to spin up to full strength. As a result, many locals turn to other bakers to get it.

But with an in-person tradeoff verboten under social distancing, neighbors in the Mission and Bernal Heights are getting creative. Some are attaching live sourdough starters to utility poles, and posting them on a frequently updated Google Map. Others are bartering with neighbors, or buying from local bakeries that have gone delivery-only.

Most of the starters currently on the Google map are the "descendants" of a single starter named Godrick, started by Bernal Heights resident David Reber. Reber says he began raising Godrick shortly after the news broke about increased COVID-19 cases in Italy.

"I expected some supply shock," Reber said via phone. Thinking about what he could do to minimize grocery-store trips, he realized that bread would be a key essential, which inspired him to stockpile flour and make the starter.

"When I have to ride out the apocalypse, I wanted to bake really good bread," Reber said.

When Reber posted on Nextdoor to see if anyone else was looking for sourdough starter, he expected some interest. But it's been significantly more popular among neighbors than he anticipated.

He's now tacked up more than 20 bagfuls of starter on utility poles in his neighborhood.

Photo: Rahim Packir Saibo/Flickr

Others have turned to their neighbors to get around the yeast shortage. Mission residents Karina van Schaardenburg and Jason Wexler initially decided to bake bread because "we thought it might not be safe to buy," Wexler said.

The couple were able to get flour at the grocery store a couple of weeks ago, but the store was already out of yeast by then.

A neighbor stepped up and agreed to exchange some yeast for beer. Van Schaardenburg said she and Wexler left the beer outside of their door, then closed it before the neighbor came to exchange it with the yeast, to practice proper social distancing.

For those who can't access starter from generous neighbors, local bakeries are also selling it. On Postmates, the Tenderloin's Mr. Holmes Bakehouse is offering a $25 kit that makes one loaf of country white bread, including a starter, flour, yeast and an instruction guide. Thorough Bread and Pastry (248 Church St.) has starters available for pickup for $5.

For those who are dealing with starter for the first time, Reber recommends investing some time in YouTube tutorials on how to properly store it, maintain the ideal temperature and feed it so it'll stay alive for the weeks to come.

Troubleshooting with experienced friends can also help. Van Schaardenburg said that some of her friends now have a Slack channel, where they share tips and post photos of what they're baking.

Newbie bakers have also shared results on Twitter, while the hashtag #quarantinystarter is trending on Instagram.

Besides the need to avoid grocery trips, Reber says he understands why starter has suddenly taken off in popularity among self-distancing San Franciscans.

"It's time-consuming to care for a sourdough starter, which can be a good thing right now," he said.