Question
I'm an inexperienced landscape chair for our community in South Florida.  A few residents would like our association to put lava rock around our shrubs, trees, etc., others feel mulch is a better product.  Which is best for retaining water and improving the plant's/trees condition?
Thanks for answering!

Answer
Mulch is far superior to lava rock. The reason is because lava rock won't deteriorate and decompose into organic materials. That's because it's not an organic material. Mulch, on the other hand, is organic, and organic creatures (like you, me, and the plants and trees), need to eat/absorb other organic materials in order to live.

Mulch will also be much better at reducing the temperature of the soil around the plants and thereby reducing the temperature throughout your community and will hold water better, thereby reducing your watering needs and your water bill. The more organic material the better.

It should also be less expensive to buy.