Sedum

shirleypaver

Hello, I am just learning about gardening and wondered if anyone can advise about sedum please. We have two large plants and last year they had a beautiful mass of flowers. These were lovely right through the winter as they turned brown.   Around February I cut them down to just above ground level.  They have come back stronger but have splayed out so they are taking up so much room but there’s nothing in the middle. What did I do wrong?

Fairygirl

You haven't necessarily done anything wrong at all @shirleypaver
They tend to get a bit top heavy, especially in wetter conditions where they can grow a bit lush and floppy. If the soil is also rich, that does the same. They do best in quite poor soil that's free draining.
However, many people do what's called the Chelsea Chop. That just means cutting them back at around the time of Chelsea Flower Show. That only works if you live in a milder area where they're big enough at that time of year though.
The other alternative is to provide some support - either a physical, man made one, or by using other plants. 
They also benefit by being divided, like many perennials. If they've been there a while [several years] you can do that. It rejuvenates them.