Ice-coated plants in the Native Plant Garden (Photo: Susan Day)

January brings cold and snowy days to the garden as well as indoor planning for the next growing season. It’s a good time to envision new gardens, consider additions and changes to existing gardens, learn more about plants best suited to your site, and begin compiling plant orders.

The most important consideration is to match plants to your site conditions. For a new garden site, note the amount of sunlight per day during the growing season, the soil type and moisture, the slope and aspect of your area, and drainage patterns. South- and southeast-facing slopes without shade will be warm compared to north-facing slopes. Microclimates near buildings or under large trees may provide small areas for plants that won’t thrive elsewhere in your plan.

One of the Arboretum’s goals is to increase the abundance and diversity of native plants in the landscape. In an existing garden, which plants have been successful? Consider adding species that grow with those species in natural plant communities. Plant finder lists like those from Xerces Society and the National Wildlife Foundation, as well as reference books* like Vegetation of Wisconsin and Flora of the Chicago Region, may be helpful. Seed mix lists from native plant nurseries may also guide you to successful plant combinations.

If you notice plants that are not thriving, moving them can be a solution. For example, sun-loving plants grow poorly in areas where shade is increasing. Consider moving them to more open areas or south-facing edges with light shade. If a large tree is removed, shade-loving understory plants, now exposed, can be moved to shadier spots. Plants that require more sunlight can be planted or moved into the new open space. It is best to transplant them early in the season and not during blooming. Soil type and soil moisture are also important – especially for species that require well-drained soils (such as in dry areas or rock gardens) or those that grow well in wet soils (such as in low-lying areas).

If you are planning for a large space or have new construction, you could consider local versions of the Wild Ones garden designs or rain garden designs available through the Wisconsin Department of Natural Resources. On a smaller scale, creating a new garden bed by using a plant mix matched to your site is a good approach if you have limited time, budget, or simply want to learn more as you go. I recommend planting small plants or plugs 12 inches apart in a prepared bed. For example, 32 plants will cover a 5-by-9-foot area (allowing a margin at the edges of the bed). You can add plants to this area after you gauge success of the initial planting, which will fill in and may self-seed in future years. Adding a few native plants into existing ornamental plantings is another option.

The Friends of the Arboretum online plant sale is now open through March 15. A wide range of native species are available, including savanna, rain garden, and pollinator mixes, hummingbird and monarch kits, trees and shrubs, and flats and half-flats of wildflowers, grasses, and sedges. To help you in your planning, plant information sheets are available online.

—Susan Carpenter, Native Plant Garden curator

*These books may be used by appointment in the Arboretum research library; contact Susan Carpenter for scheduling.