It is one of those "I do not understand it" facts that when dahlias are planted into an area where they have not been grown before or at least they have not been there in 10 years(just a guess), that they grow really well. At a local commercial farm, they used an area for the parking lot for very many years. They changed the layout and it became another dahlia field. The owner said it was by far the best area in his very many acres of dahlias. Years ago, an enthusiastic grower bought an old house with big lot and the lot was covered in blackberry bushes. He cleared them and said he planted best dahlias he had ever grown. However, there are lots of stories that the dahlias would not grow in the new area too.
Entrust is the brand name of the osmocote type fertilizer being sold at our local nursery supply company.(yes, there are numerous such companies in our area as horticulture is big business in Oregon). They say that it is the new name for "Apex" fertilizer that for many years was manufactured by the JR Simplot company. It is "only" about $87- for a 50 pound bag of the 14-14-14 3-4 month time release. We will stick with our favorite brand(Haifa) , if we can still find it as who wants try something new when the old one does so well. But if it is not available we 
have a back up.
