This is the 16474th most frequent Russian word.
садоводам
"To gardeners" (dative plural form of "садовод").
In this sentence, 'садоводам' is in the dative plural form, showing that the book is to be addressed to or is intended for gardeners.
Эта книга будет полезна всем садоводам.
This book will be useful to all gardeners.
Here, the word 'садоводам' is again in the dative plural form, indicating the recipients of the souvenirs (gardeners).
На выставке мы подарили сувениры садоводам.
At the exhibition, we gifted souvenirs to gardeners.
'Садоводам' signals the intended audience of the recommendation, again using the dative plural form to express the idea of addressing gardeners.