I saw in the internet and facebook that the expat ask for the place can buy plants in Saigon.
I suggest some places in Thành Thái street district 10. There are a lot of garden shop and you can find whatever you want for your garden. If you are living close to district 7, you can visit a big shop in the intersection of Nguyễn Văn Linh and Nguyễn Hữu Thọ or some smaller shop next to Lotte Mart.
Also I have a small online shop sell succulent and mini pot for garden. We provide many kinds of succulent, pot…to beautify your office, enhance your garden or as a cute gift for your loved one. If you want to buy some, you can contact me.