Learn German: Die Blume wird gelb. - The flower is turning yellow.

While werden is used as a helper verb to build the future tense (like 'will' in English), its actual meaning as a main verb is 'to become' or 'to turn'. Because it is the only verb in this sentence, it means the flower 'becomes' or 'turns' yellow.

Where is the 'is -ing' part of the sentence for 'is turning'?

German does not have a separate continuous tense like English does. 'The flower turns yellow' and 'The flower is turning yellow' both translate to the exact same simple present tense in German: Die Blume wird gelb.

Since die Blume is a feminine noun, why isn't the word for yellow written as gelbe?

Adjectives only take an ending when they are placed directly in front of a noun, like in the phrase die gelbe Blume. When an adjective comes after the verb to describe the subject, it always stays in its basic, dictionary form.

Is wird an irregular verb form?

Yes, werden is a strongly irregular verb. For the third-person singular (he, she, or it), the core vowel changes from 'e' to 'i', and it takes a 'd' at the end. Because die Blume acts as a third-person subject, the verb becomes wird.