Would anyone like to help me solve a rather tedious puzzle?

[sprigatito]

I have several sets of these garage racking sets, which I would like to put in my new greenhouse. Unfortunately the cheap crappy MDF shelving boards are completely rotten and useless, so I need to replace them with something, preferably something that can withstand being wet on a regular basis. Any ideas? DH suggested chicken wire, but I’m not sure how we’d secure it, and it might not be stable enough to hold loads of plants without bowing. I’m stumped!

(I told you it was tedious!)

What about a box of tiles? Measure the shelf size and have a look for floor or wall tiles that fit.

B&Q will cut wood to size. Would plywood with waterproof sealant work?

Wbp plywood or marine ply would work (am a joiner )

Oh, great ideas! Tiles is an interesting idea, waterproof and might be cheaper than getting wood cut to size

You need something like wire fencing, or even cooling racks for baking (maybe catering sized).

I had wire mesh in a plastic greenhouse.
It went rusty.

i wonder if you can get thick plastic or plastic coated wood or something these days.

Maybe composite decking would do? Or just thick planks of wood. Wooden bridges outside in the golf course etc last for about a decade.

You can get plastic “wood” formed into timber cuts, we used it under our shed as a non rotting base!

You could consider something that's essentially racks instead of solid shelves. My DH made me some greenhouse staging like this - pic is of the underside of a shelf, turned on its side. I use it with plastic trays or saucers for pots, and just as it is for storage of pots, utensils etc. It's lasted more than 15 years. I would also consider something like floorboards cut to length. It won't matter if there are gaps between them.

I suspect that your shelves are structural and if you replace them with something less solid you may have issues with the stability of the whole thing, but that's easily solved by putting a cross piece across the back.