Ask Mr. Smarty Plants

Well, if you are over the age of 25 you probably realize that you can't always get what you want, but you can get some of what you want. 

Our Native Plant Database  will  generate lists of plants according to your criteria, using the Combination Search feature.  It is not organized to search for Ground Covers but if you search All Habits and narrow by height (0-1 and 1-3 feet) you will get plants that will do the job including herbaceous perennials, ferns, grasses and small shrubs and vines. Each plant on the list is linked to a detailed page that will give you information about flowering period and light and moisture requirements.  You will find that by requiring evergreen plants you really have to compromise on flowering period, since you live in the north. You say you are looking for plants for sun and shade so you will find some variety, but your biggest challenge will be competition for moisture under those trees.

When I do a search without narrowing for light or moisture conditions, a list of 53 plants is generated, but when I narrow for dry conditions there are only 14 left; and that list reveals a weakness in our database.  There are a few plants with a very broad native range like Coreopsis lanceolata (Lanceleaf coreopsis) and Callirhoe involucrata (Winecup) that are listed.  They may be evergreen in Texas, but they sure aren't in Harrisburg, PA.  You may decide their flowers are worth sacrificing the evergreen quality!  Coreopsis has a very long bloom period, winecups' is shorter but as it is a member of the mallow family, it has hibiscus like flowers.

Here are a few from those lists to consider:

Arctostaphylos uva-ursi (Kinnikinnick) and Gaultheria procumbens (Checkerberry) have flowers and red berries to lengthen their season of interest.

Mahonia repens (Creeping barberry) has yellow flowers, interesting fall colour and grape like fruit

Lycopodium digitatum (Fan clubmoss) is an easy care woodland choice that looks like cedar and Carex blanda (Eastern woodland sedge) has it's own spiky charm

If providing irrigation water is something you are willing to consider, your choices will expand considerably.