Compost which actually absorbs water.
I've used a well known compost which claims to retain more moisture for a few years and always had good results. This year is very different. I use a drip watering system and previously it has kept the compost nicely moist, and there would be a light trickle of water out the bottom of the pots just before the water turned off. This year the water is running virtually straight through and running out the bottom. There is a small core of wet compost and the rest is bone dry. In other words the water is not spreading through the compost.
It looks like I'm going to have to stand each pot into a deep saucer and try to get the water to soak in that way.
It's a bit late for this year but can anybody suggest a compost for pots that they have found to be successful this year, then I can try it next year!