I suppose it depends on which flavonoids you wish to study as different plants often make different compounds. You may consider studying both the cultivated and wild plants of the same species to see how the flavonoid composition and concentration changed. By cultivation, we have changed the genetics of plants and so  that may be helpful in understanding the changed genetics for flavonoids.

I think it would be more helpful for study the genetics of  flavonoids  to use wild plants.

thanks a lot Jack Silver , Jianchao Zhang 

it good to study cultivated and wild and study the genetic diversity,

also in fact i agree than it helpful to study wild plants, but it might be difficult to grow in lab .

However, i wondered from the genetic view if it scientific and it could to study the evolution and origin of gene in cultivated plants?