Answer: There are so many possibilities that I will give you some hints on choosing plants, as I don't know your likes or dislikes or how much space you have. The most important things when choosing plants are determining what sun exposure (full, partial, shady) they will thrive in and how much space they need to grow to maturity (both vertically and horizontally), and then comparing that with what your landscape offers. Soil type is another important characteristic. In other words, you wouldn't want to put a huge sun lover in a tiny, shady location. This seems obvious, but many people forget it when they go to the nursery and are confronted by all sorts of beautiful plants. Analyze your site and think about what you want from plants (color, shade, cut flowers, bird attraction etc.) then choose plants that fit that situation. Here's a list of plants that take varying amounts of shade for your northern exposure. I hope it gives you some ideas. Also, try to go to a nursery and look around. Plants under canopies or cover are usually the shade-lovers and those without cover take sun.
Flowers for shade: Perennials -- Anemone, Columbine, Astilbe, Campanula, lily-of-the-valley, Dicentra, Digitalis, Ferns, Hosta, daylilies, Liriope, Monarda, Pachysandra, Thalictrum, Vinca, navelwort (Omphalodes cappadocica), blue lungwort (Pulmonaria angustifolia), pinkroot (Spigelia marilandica), bellwort (Uvularia grandiflora) and sweet violets (Viola odorata).
Annuals -- Begonia, Browallia, Coleus, annual Foxglove, Forget-me-not, Impatiens, Primrose, Torenia, Viola. Bulbs -- Begonia, Caladium, Camassia, Elephant's ears, Lilium, Narcissus, Scilla, Callas.
For shrubs, you might consider viburnums, hypericum, paxistima, shrub dogwoods and hydrangea arborescens.
Evergreen shrubs: yew, boxwood
Moist soil woodland plants: There are many woodland flowering plants that thrive in moist soil and shady conditions. Consider baneberry, pearly everlasting, goat's beard, bog rosemary, astilbe, ferns, marsh marigold, sedges, sweet woodruff, japanese iris, bloodroot, and black snakeroot.
Here are some perennials that are 2-3 feet tall: digitalis (foxglove), daylilies (hemerocallis) (some prefer full sun, but some will take some shade), liriope, monarda, columbine, Asiatic lilies, or astilbe (false spiraea), which has many varieties of many heights, but some would be in your preferred range. Sometimes a shady northern exposure can be difficult for blooming plants, so you may need to experiment with a few varieties to find what performs in your spot. Good luck!
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