1 adenium watering tip you need to know is this succulent hate being waterlogged. High humidity can mean that your watering schedule will need to be altered. The best fertilizers for your plants are those that have a high phosphorus content. Clay retains water so soils high in clay won't drain fast enough for succulents or cacti. These species of mature cacti plants often have woody barks, which look very much like trees. Interestingly, they have a Best Selling Book: Cacti and Succulents: Choosing, Styling, Caring by the shop's owner, Gynelle.