So I was browsing the house plant rack at wally world and saw some Begonia rexs. Most were piles of mush due to over watering. But about 2 still had leaves and I bought the best looking one. It even has a few flower buds.
I have killed two or three in the past many years ago by potting them in pure potting soil. This is before I learned most of what I know about plants today.

This time I planted it in a gritty mix. How often should I water it and how much light does it need?

Pretty, I'd rescue that too!

Over winter, might need some direct light to stay looking good. In a windowsill like that should be great. During summer, that can be a bit much, depending on location/latitude, time of day, heat.

Rex are rhizomatous type. The rhizomes store moisture, and can rot easily if there's not tons of oxygen, as you've seen, should do fabulously in the gritty. Water when dry, don't let plant get wilty. There's so much written about Rexes and rhizomatous Begs in general, you should be able to find enough reading material to keep you busy for weeks.

Gotta love it, rescue plants are a favorite (in general) of mine.

Never had great luck with "rescue people" but I have with "rescue animals".

"Rescue plants" though, sometimes free from places I work or adjacent property lines but most often from "almost thrown-away" racks at retailers. My favorite as attachment and initial cost are minimal.

Here's a fine example I potted up this morning, a "Tropicanna" canna from Lowes. I'd never seen them and broke down and paid $20 for my first even though I thought the price was ridiculous. Had to hit the nursery a month later and all were sold. Actually, many ended up on the distressed plant rack at $10. After an agreement with the dept. manager on duty to take them all, $5 per specimen. Not my best canna season so the previous occupant of this pot was exchanged for this soon-to-bloom "rescue".

This particular plant needed a little love to look as good as it does now. Five bucks? What's not to love! In 2 weeks I'll swap in a mum, get this one a well mulched spot in the garden and wait until it's time to dig and store.

Can't advise much on the begonia but best of luck!

Great rescue Adam, they are going to do really well with your TLC.. I've found some great finds at WallyWorld for dirt cheap

I got a very over-packed 4in. pot of Rex begonia at HD for $5 a while back. I turned it out of the pot and was able to divide it up into 10 smaller plants. As of this year, I have about 6 large pots of that begonia around the yard, they are beautiful!

Highly recommend dividing if the pot is crowded, they take very kindly to it. In this pot, 3 small divisions filled a 9in. pot in about 2 months.


Lower left in this pic are the most recent divisions of divisions of that first little pot.