What do you all mix with your compost in different situations? (e.g. pots, planting flowers/shrubs in beds, veg plot). I don't do anything apart from add a bit of grit if I have some for my clay soil, but wonder now if I'm missing something that will make my planting success rate a bit higher... I watched a bit of Gardeners World the other day and the presenter was using a mix of compost and perlite and I don't even know what perlite is. Feel I'm missing out on a key chunk of gardening knowhow. Thanks.