Gardening with Native Plants: Planning Season

hoar frost on milkweed pods

Hoar frost on milkweed pods

During January, gardens are typically quiet, snow-covered, chilly, and dormant. It is an inviting time to envision additions and changes to your garden, consider adding more diversity to plantings, and plan for color and growth. Sketches, contours and slopes, plant lists, and imagination can come together, shaping garden possibilities and decisions. Native seeds, stratifying under snow and germinating in native plant nursery greenhouses, will yield plants for gardens when spring arrives.

This month’s article, and the next two, will cover three home gardening situations that I commonly encounter in requests for garden advice: semi-shade gardens, rain gardens, and low-profile (shorter) native plant gardens. Other valuable resources include basic information about growing native plants, design ideas, and the Friends of the Arboretum plant sales.

Native plants with white flowers blooming near an oak tree
Savanna plants blooming under an oak tree in the Native Plant Garden

Many home gardens have at least some shaded or semi-shaded areas. The north side of a house or garage provides a shadier, cooler, and moister microclimate than other exposures. Small trees or trees that cast light shade – due to a high canopy and/or fine-textured leaves – allow understory plants that tolerate intermediate light levels to grow well.

Large trees to the south in neighboring gardens may cast shade over a garden without its own trees. For these sites, shade-tolerant shrubs like dwarf bush honeysuckle (Diervilla lonicera), ninebark (Physocarpus opulifolius), and nannyberry (Viburnum lentago), and herbaceous savanna species are well-suited. Shade-tolerant sedges like Penn sedge (Carex pensylvanica) and Sprengell’s sedge (Carex sprengelli) are good choices to fill in between forbs (non-grass plants with flowers) or as a green matrix where other plants can be added over time.

In deep shade (areas receiving less than 2 hours of direct sun per day) with rich soils, woodland species, including spring ephemerals and many ferns, will do best. These plants are usually slow growing and often less available from nurseries. It is practical and economical to start with a few plants and build a shade garden gradually with species that spread by rhizome or seed once established. Examples include wild ginger (Asarum canadense), woodland phlox (Phlox divaricata), and wild geranium (Geranium maculatum).

Woodland phlox blooming in the Native Plant Garden
Woodland phlox in the Native Plant Garden

Turfgrass areas that have become too shady are suitable spots for planting diverse “soft landings” within the dripline of trees or encouraging moss gardens. In dappled shade, savanna plants can also be used directly under the tree canopy as well as in sunnier areas nearby. While some species can span a wide range of light conditions, you may notice differences in height or flowering in shade versus sun.

If you are especially interested in gardening for pollinators, Xerces Society has created a series of habitat assessment guides, including one for yards and gardens. With this guide, you can evaluate your garden now, use a varied checklist (page 4) of activities, and then assess your garden later to see how you are improving aspects of pollinator habitat. The checklist can also be used on its own throughout the season, as an action plan tailored to your site.

Shady and semi-shady gardens usually have very few weeds, and soils may retain moisture longer than sunny gardens. However, in drought or when only light rainfall occurs (and does not come through the tree and shrub canopy), you may have to spot water establishing plants. After establishing, native species will rarely need supplemental watering. You can eliminate fertilizer and pesticides and planted areas will not need mowing.

Whether in shade or sun, growing a wide diversity of native plants matched to your site conditions will improve garden resilience to heat, drought, and excessive precipitation, as the plants have a range of adaptations and responses to survive these weather extremes. Enjoy garden planning in January.

—Susan Carpenter, native plant garden curator