Hay cultivated with garden plant (9)
I believe the answer is:
hydrangea
'plant' is the definition.
(I know that hydrangea is a type of shrub)
'hay cultivated with garden' is the wordplay.
'cultivated with' is an anagram indicator.
'hay' anagrammed with 'garden' makes 'HYDRANGEA'.
(Other definitions for hydrangea that I've seen before include "Showy flower" , "Shrub - garden hay (anag)" , "Plant's" , "Shrubby plant with showy flowers" , "This flower is strangely a hay danger" .)