Valley View Farms has long been recognized as the best in the area for anything you need for your garden--their nursery and greenhouse are huge and they have beautiful specialized things--pants for water gardens, plants to attract butterflies, etc. Most of the staff is helpful, although some are just high school students with little experience or knowledge, but if they don't have an answer for your question, they will find someone who does.
One thing that makes Valley View different is that going there is more of an event than a shopping trip. When the gardening season starts to wind down, they become a destination for Halloween fun--including a huge pumpkin selection. And their Christmas shop (which starts over Labor Day) is insane--it reminds me of the tree lot in the Charlie Brown Christmas special. Definite sensory overload, but fun.
Their prices are higher than average, and from my neck of the woods, it's a bit of a hike (I prefer Garlands) so I don't shop there often, but it's worth it when I do.