You're not gonna believe this, but my Ti's (all from Hawaii as my next door neighbor is Hawaiian and makes 2 trips a year), are full and healthy and have been growing in straight SAND and I've never fertilized them.

The ONLY water they get is either from the rain, or from my washing machine. I ran the drain from my washing machine (which used to dump into the septic) into PVC piping, ran it around the back of the house (which used to be a complete desert wasteland, I live in scrub) and drilled holes into the last 6 ft of pipe going from large holes at the start of the back of the house, to smaller holes (nearer the end of the pipe)...Now I have Hawaiian Ginger that propagates itself, calla lilies, papyrus, 3 kinds of ferns, Ti, crotons, broms, aloe, caladiums, arrowhead, peace lilies and flame vine (probably more, it's a jungle) all growing and reproducing like mad...guess they like the washing machine water, lol. I DO use organic laundry detg...

Don't take them too seriously..mine have seemed much better if they're sort of left to their own. I cut them down and make them fuller once in a while (they send off side shoots).