The pandemic has changed the national cannabis landscape. While many other businesses buckled, some of the industry was deemed essential, and sales over this past year have contributed to what has now become a more than $18 billion industry in the United States.

First-time users could have driven some of that boom. One California delivery service says purchases from beginners were up more than 50% early in the pandemic. And now that stimulus checks have started to roll in, some newbies may be thinking about buying more green...