This has to be one of our favorite genus right now. Astrophytum are incredible little cacti native to parts of Mexico and are known for their odd shapes and variety within the genus. They have adorable flowers that occasionally form at the head of the cactus almost looking like a little crown or hat. They are notoriously slow growers but as they mature they swell and swell and can reach about 1ft tall. We discovered last winter here in Portland they are cold hardy outside up to 25 degrees which is pretty impressive. Though this makes sense in their native habitat they will reach incredible temperatures during the day and freezing temps at night.
These would do best in a bright filtered light if not in direct sun. These can go long periods without watering. They will like full waterings roughly every 2-3 weeks in the summer when the foliage starts to feel less firm. Watering can be cut back to roughly once a month in the colder months. They will need a super coarse cacti soil mix when repotting.