I have a very very old staghorn fern that I brought with me when I moved from sunny Southern California to Southern Oregon. Last Winter the staghorn made it through the Winter just fine with a plastic cover over it (what do I know). BUT this Winter we had severe low temps and I purchased a plastic 6x8 greenhouse just for the staghorn. I put it in after the first frost and of course it took a hit. One side looks dead (perhaps). The rest of the growth looks like it is coming back. In 30 years of owning this plant I have never fertilized it with anything but banana skins. One of my gardening friends told me that a local nursery sold her some cactus food and her staghorn is flourishing. What do you think? I went to two locations and could not find cactus food. Need some suggestions. Thanks