Cindi ... you have to keep in mind that container soil and container type for Khalid's climate may not be perfect for your climate as your climate is more humid and gets much colder during the winter months. The ambient temperatures really do make a difference in the type of soil mixtures and containers that work in a given climate.
Although I have the high summer temps in the high 90s and low triple digits container gardening is a nightmare for me because there is a 40 to 50 degree difference between my day temps and night temps. If I water for my day temps only, I can easily end up with root rot. If I don't hydrate the plants well enough, I end up with fried plants. I can do it, but, for me, it requires a lot of care and attention. In San Diego, it was almost a no brainer because I didn't have to deal with major temperature fluctuations.
Clay pots with a heavier rock content in the soil won't wick the water away from the soil which is probably why they work well in Khalid's climate. The soil mixture with that kind of rock content also is why plastic would not work well. The soil mixture as well as the ambient temperature and humidity dictates the type of container that will be the most effective in a given climate.
I agree completely about avoiding peat in a hot and dry climate. If peat ever dries out, it repels water. I have actually used it to control invading bind weed. It's like putting down concrete. Nothing will grow through it. I haven't found any commercial potting soil or compost that did not include peat, so if you can find organic material to make you own mix, you are way ahead. However, if you garden in a climate where it is not going to dry out completely, you are not going to have the same problem.
So, "it depends."
The real take away is Khalid's willingness to observe and experiment to find what works best in his/her climate.
btw ... Khalid, I am very impressed with what you have shown us with your roses and thank you for sharing what you have learned from them.
Edit ... forgot a word ... oops !
