I buy many rescue plants and some have looked like on death's door. So I do this all the time
I bought 5 today for 7 $ that look like crap!!
One thing I do that helps a lot is as soon as I get plant home I clean it up. Then I soak overnight in a container filled with Plant Starter/UpStart.
In a few weeks I usually have a nice looking plant. Best one this year so far was a hanging basket of Calibrachoa. Most peeps would have tossed it in the compost heap. I paid 3 $ for a 19 $ plant. Now it is one of my loveliest on my deck. And from experience I know I can over-winter in my garage so get to enjoy next year too.
