The word "although" means that the next words are true. Let me re-write the first clause (subject + verb) of the sentence (which contains two clauses) .... "It is true that these flowers may be able to live without my help". Then, in the sentence we see the second clause and the first and second clauses are connected by the conjunction "however". "however" means that the following text/words/thoughts are telling us some additional information and we should learn this information or at least think about using this information. Let me re-write the second clause "..., however, I never ignore the flowers because if I don't take good care of them, they will probably die. So, yes we can use although and however in the same sentence because they are not being used in just one clause. Hope you understand... good question.

The sentence above is incorrect anyways. "Although such flowers are able to weather through by themselves, I never ignore them or abandon them to their own fate. For otherwise most of them will probably end up dead."