'أيُّها' originally compound of (أيُّ and the attention seeker particle ها التنبيه) and with أيَّةُ for feminine (أيَّتُها), is a vocative connector used for nouns bearing the definite article 'ال'. You can say يا أيُّها الرَجلُ (O you man) and you can drop the vocative particle and say أيُّها الرَجُلُ. Example : أيُّها السادة، أيُّتها السيدات (Ladies and gentlemen).

In Arabic we use the article " يا " to call someone ex : يا محمد ، يا أحمد and the noun after يا is called المنادى ( almonada ) , but if this noun المنادى begins with ال we need to put أيها before this noun if it is masculine and أيتها if it is feminine like your example we put أيتها because the word الزهرة is a feminine.