Looks like they might be closed for the winter, but they're definitely open spring/summer/fall. I bet come March they'll be open. Can't recommend this place enough

Ricky's Flower Mart is a good choice. Knowledgeable staff. Certain large plants can be pricey but they have a great and (usually) very healthy selection. Best to go in the spring though, I think they stock less variety in the winter. There's also parking

It's not directly in Cambridge, but Planned Parenthood near BU is excellent and accepts all sorts of insurance. They can provide whatever you need