I suggest a read of Wikipaedia on the subject of silica gel. I have used it for some time now. At the simplest level it is based on silica which is a natural product sourced from sand. Those little packages found in shoe boxes and the like, are another use My brother used to cart liquid silica about in a tanker for ages. Wiki says been known of since 16.....whatever. I never see any remains of gel when I tip out my pots around this time. Best to read up about it, and make up own mind. I would point out that water is our most vital commodity, and this does save waste of water. Especially if movable pots are watered from the bottom.

How do you water a pot from the bottom? Does this mean standing it in a tray of water?

Hi Bryony. I stand my SAFELY movable pots in a large rubber trug and they drink what they want. I have to remember they are heavier after watering ,so there is a limit. My butt near the house lasts much longer in a no rain time, this is Essex. I try to water other larger pots so that water does not run out the bottom too much. We are metered, so I try to avoid the hose. It's just me and my ways. Everyone has to mind their back and get some exercise too if possible.

I starting using the watering gels two years ago. Last year I tried some on my Hydrangas, I figured I'd try it since I was watering them 2-3 times a day. It works. I use Maricle Gro and some generic brands of instant fertilizers too. I use a sprayer and I mix insect teatment at the same time. I used to use a watering can, but now that I tried the gels, I don't water as often, sometimes I can go 2 days in the heat without watering.