Gardeners have told me that they have difficulty growing rhododendron in new castle and one individual at a nursery told me that rhododendron will only last two years in this area because of recent disease pressure. Is this true? And what colorful bush/shrub under tall evergreens would you suggest?
Rhododendrons aren't necessarily a problem unless your soil is very clayey and compacted. With poor drainage, rhododendrons will probably not do well. What tall evergreens are you talking about? I am guessing white pines since they open up at the base. Most evergreens are branched to the base, so it doesn't make sense to plant under them. It is unclear whether you are looking for low, medium or taller shrubs. It is also unclear whether the ground is moist or dry. Dry shade is one of the hardest areas in which to plant. Our Livable Plants for the Home Landscape brochure (http://extension.udel.edu/lawngarden/files/2012/06/lowres18spreads.pdf) suggests oakleaf hydrangea for dry shade. Hairy alumwort (Heuchera villosa) is also a good dry shade plant, as is Barrenwort (Epimedium sp.) - the last two are both perennials. You can also get color from foliage and can plant Carex sp. and Hakonechloa in dry shade. They can be variegated or chartreuse. If the soil is moister, try Viburnums, Clethra, Fothergilla, Caliicarpa or a whole bunch of perennials that will add color to a moist shady location. If you look at the brochure, you can find these suggestions and more.