Cannabis connoisseurs won’t be the only ones rejoicing if voters legalize recreational marijuana this election. Expect Silicon Valley’s burgeoning class of pot entrepreneurs to join the party.

Startups are cropping up throughout the Bay Area that put a signature Valley spin on the age-old practice of selling marijuana, offering sleek on-demand delivery apps for users and high-tech software for growers and dispensaries. The business models are risky — marijuana is illegal under federal law and stigma around the drug prevents cannabis startups from scoring funding from many major investors. But with recent polls suggesting Californians are poised to expand marijuana consumption beyond medical use, experts expect cash to pour into the industry.

“It’s going to blow open the doors to innovation on the technology side of the cannabis industry,” said Chris Walsh, editorial director of Denver-based Marijuana Business Daily.

But he warned that startups will have to navigate a period of uncertainty and chaos while lawmakers figure out how to regulate the...