How do you learn foreign language vocabulary, beyond Anki?
If all you want is be able to read, I don’t think translation flash cards are the way to go (these are useful if you want to to be able to quickly find a corresponding word in your native language). When learning to read in foreign languages, I create flash cards where the “question” is a sentence in the target language (German in your case) with one unfamiliar word, which I put in bold. I succeed if I correctly understand the word in the context of this sentence. In the answer, I put the definition in the target language (German here) for the appropriate sense.
Usually, this is enough for me to understand the word when I meet it in new sentences, assuming it’s used in the same sense. In cases where I failed to learn it, I just add a second flashcard with a new sentence containing that word.
For “encyclopaedic” words like species of animals or plants, kinds of food, towns, etc. it’s in fact more useful to put a translation in your language rather than a definition in the target language, assuming it is a familiar concept in your own language. (And not try to learn several similar animals, plants, … at once, otherwise I mix them up.)
I usually take the sentence from a dictionary targeted at learners (sometimes I use the sentence where I found the word, if it’s the only unfamiliar word in it). For English, I use The Cambridge Learner’s Dictionary. For German, Langenscheidt Großwörterbuch Deutsch als Fremdsprache might be a good one (what’s important is that there are example sentences).