April in Wisconsin brings anticipation for spring and daily changes in plant emergence and bloom. In the prairie gardens, favorites like pasqueflower (Anemone patens) and shooting-star (Primula meadia) bloom, soon to be overtopped by taller prairie flora. On the deciduous forest floor, a diverse ephemeral spring flora has an even shorter time “in the sun.” If you have a shaded garden or want to develop one, the spring woodlands teach and inspire.
How much shade do you have at your site? A woodland planting may be suitable in an area with mature trees or near the north facing side of the house if the soil is usually moist. An edge area can be planted with woodland natives if it is not too exposed. I recommend using leaf mulch on your beds (easily provided if you have mature trees) to retain moisture. Because it can be difficult to judge the amount of shade on a site, I recommend visiting established gardens and woods to gauge success for your site. Spring Woodland Wildflowers of the University of Wisconsin–Madison Arboretum and the Friends of the Arboretum Native Plant Sale list are useful sources for information about matching sites and plant needs.
Consider the pattern of growth for woodland species. Spring ephemerals will have completed their annual growth and reproduction by the time the tree canopy has closed. Gardens of ephemerals are beautiful early in the season, but plan for mid to late-season interest. Other early blooming species like bloodroot (Sanguinaria canadensis) and Jacob’s-ladder (Polemonium reptans) remain green throughout summer. Because early spring species are short, include taller plants that persist longer, such as mayapple (Podophyllum peltatum) or red baneberry (Actaea rubra). Ferns such as tall interrupted fern (Osmunda claytoniana), delicate maidenhair fern (Adiantum pedatum) and arching lady fern (Athyrium felix-femina) will provide more variation in foliage, form, and texture.
Here are some other suggestions for a woodland border. To give height to a planting under mature trees, try shade adapted nannyberry (Viburnum lentago), bush honeysuckle (Diervilla lonicera), or fall-blooming witch-hazel (Hamamelis virginiana). Wild ginger (Asarum canadense) and Pennsylvania sedge (Carex pensylvanica) will grow and spread well as ground cover in intermediate shade. For fall color in a shaded garden, include elm-leaved goldenrod (Solidago ulmifolia), zig-zag goldenrod (Solidago flexicaulis) and Short’s aster (Symphyotrichum shortii). These spread well by seed and/or rhizome, so you may want to control them a bit.
Plants for a diverse native woodland border and your sunny garden areas will be available at the Friends of the Arboretum Native Plant Sale on May 12. Mark your gardening calendar, and see you there!
—Susan Carpenter, Arboretum native plant garden