Hi! Gardening newbie here. I am nervous about asking this because it sounds like something I should know.. but bear with me.. I really don't know who to ask.

I have an big open balcony outside my room. I have been gardening there. I have three big pots of bouganvilleas and 2 random garden plants in big pots.

I have recently gotten bit by the cacti and succulent bug! I now have about 15 small pots of cacti. They just rest (temporarily) on the (thick) balcony edge, under the awning. Some of them are also indoors in the window sill that faces the balcony.

ANYWAY I want to buy some sort of stair-type shelving so they have a proper home.

I have Googled ideas and checked home stores and I have question.

How come most of the shelving being sold or in photos are wooden or iron?

I don't understand this. I live in Asia. VERY humid and hot. We have sun year-round and half the year we get rains. My balcony in question is open.

If I leave any wooden item there, it will grow disgusting mold/fungus almost overnight. It freaks me out. I had to saran wrap a wooden table (I was terrified of the spores) and hoist it down the balcony into the trash. Mold was neon (lol) and I didn't even want it inside my house!

I also left some garden tools there and in weeks they got rusty at the hinge area. I am sure an iron plant shelf would look good for months then eventually rust. (Right?)

SO NOW, on to my question.. am I left to find some sort of PLASTIC stair-shelf for my cacti collection? Can you imagine how ugly that will be? Haha.

What do people normally do? What do I buy? Not wood.. so what then? Iron? What kind won't rust? Any ideas would be appreciated. Many thanks!