rock vs. potting soil

I am wondering if cactus and bromliad can be potted in rock instead of soil. Will I get the same results? Will the rock retain enough moisture for the plant to survive? It is getting cold out, so my plants are inside now.

Have never grown Bromeliads because the only way suitable for me would be withing the bathroom where they could get the moisture droplets from evaporation when hot showers etc are used, also they live in there natural habitat attached to trees etc, the roots are sustained by mosses growing on the host tree, a bit like some Orchids, some of your plants need the flower topped up with water whereas others need the small amount of moisture at the roots, so if I were you, I would be going along to the library or book store to get hold of reading material as to how to care for them properly as it would be a shame to loose them now.
As for the Cactus, there are compost ready mixed you can buy from the garden centers with all the right food, compost they need, but I mix my own buy mixing in Horticultural sand into the plant compost and adding some very small grit into this for good drainage, again, books will help you out till you get used to there needs and honestly, it ain't rocket science, just easy when you know how, you will know that there are as many different types of cactus and Bromeliads, all needing slightly different requirements, so books will also help you to identify which ones you have, you obviously love these plants, so good luck, hope all goes well over the winter. WeeNel.

Thankyou WeeNell. I was given the bromeliad, never had one before so am not sure how to care for it. As for the cactus, I do love all cactus plants! They are fun to grow and very easy to care for. I am now in the process of finding the names of the 10 or so different varieties that I have. Naming them would have never occured to me if I hadn't stumbled onto DG. This place is very informative not to mention addicting!!! I have a small flower garden in my yard, but nothing like I hope to have next year after reading the gardening forums here. I hope the rain has finally left you for now and you can enjoy some sun, although I guess it is getting cold there now....
Beckie

Beckie, it is cold enough to need to wrap up well in the garden which I hate as it is so restrictive for doing some jobs, also it is wet and cold under feet, but some jobs are OK if I'm moving about or pushing the wheelbarrow around.
As for the Bromeliad, I was given one as a present and it flowered for months, dapple shade and watered into the florett with rain water, but when passed flowering, it died on me, when I read up on it, I discovered that some of them do that naturally, OH well I thought, that's that, but hey presto, it had a tiny new one growing from the roots, so it was fine in the end, one of my friends in the city (I'm a country girl) she had her husband cut a largish good twisted branch from a tree and has this set in a large ornamental flower pot with stones and sand for stability, she fastened her Bromelaides onto the shortened branches where they form a V, and the plants are growing onto this by wiring moss around the roots holding them onto the tree branches, and they grow on this tree, it is about 6/8 feet tall and twisted by the trees growth, but it looks so attractive, with a up-light stuck into the pot. She just mists the moss/roots when water is required and pours water (rain) into the BRACTS as the flowers are called as they are really just coloured leaves, so there's an Idea for you to get going over the winter, she has different coloured plants and FERNS, also an Orchid, and even though the roots sometimes poke through the moss, that also looks attractive, it sits in the corner of her sun room that has had shade added to the roof and window in that corner.
The Cactus are great fun, as you said, there are so many and some take years to flower, but that's also part of the fun, I grow mine in my greenhouse for hot summer sun and winter protection, some are growing in shallow trays like gravel beds, while others are in large pots placed on upturned pots for height just because they have grown naturally over the sides of the pot and it helps with drainage also. You will soon learn from books what is the best way to show them off and also what each type need cared for, remember, some actually need quite a bit more water than you think, while others will rot if the same amount was given them, so get out for a good all round easy to follow book so you can enjoy your new style gardening, you will soon become addicted and very possessive about your new learned skills. Good luck, hope you can soon send us some picture to show off. best wishes. WeeNel.