How dfo you grow a new clump of celery from the butt end?

You might need to do a bit more research with people who know https://www.gardeningknowhow.com/edible/vegetables/celery/how-to-plant-celery-bottoms.htm

The videos make it look so easy. I've had the same bad luck you have!

You have to wait to plant it until it has plenty of decent roots, it will take more than a few days.

It needs to have a set of good roots before it can go outside in the ground or pot. I have mine sitting in the kitchen and have to change the water 3 times a day, still in the 90's here. Depending on where you live, you may need to winter over inside and set out next spring. I have all my "starters" on old cookie sheets to easily move them around when necessary.

Soak it in water for weeks until you see roots. Use celery you have cut off the top and leave an inch or two. It will start growing the top again IN THE WATER. When you have good root system on the bottom and green starting on the top then put it in soil. Also, change water every 2 or 3 days to keep it fresh and set in window in sunshine

http://homeguides.sfgate.com/replant-root-end-celery-38121.html