These thematic pictures of die Natur are analogous to a visual dictionary. The theme "die Natur" is split into several parts. For children, especially toddlers from 1 to 5 years old, it is better to divide the sets of cards over several days, or even weeks, so that the information is absorbed better. This is especially true if you are using flashcards to learn german language that is not your native language.
To expand your german language vocabulary on the "die Natur" topic, flashcards games are the best way: