Meloncactus has many forms. But there are kinds that grow enormous webs of roots to survive. So if you pick/find one in nature, cut it loose and put it in a container it may survive 2 years as a result of the watersupply in their 'melon', but then dry out and die. Furthermore they are very slow growers in nature, so even if you put it in open soil, it is hard for the plant to form enough new roots to survive. Therefore, please be aware of the source the meloncactus comes from.