When thinning out seedlings what is the success rate of replanting these extra ones or should they be discarded & put onto the compost heap?

Hi, mikeymikey!

As avid gardeners, we like to try to save every plant that we can. However, not all the plants are worth saving and we hate to "kill" any of them.

However, if you have ample enough seedlings of one particular variety of whatever it is that you're wanting to plant, then I would discard the ones that appear to be weak. You can spend time with trying to nurture the weak ones, and, they might grow into good plants, but the time and effort to do so would probably be better spent nurturing the ones that would appear to show some promise of being successful in their growth.

That's part of the purpose of thinning out the seedlings - to be able to let the strong ones grow and to be able to spend the time helping them to do so.

Thanks!