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Three useful species for many landscapes
Easy to grow, easy to manage, well-behaved and problem solvers for shady landscapes: all the criteria for go-to plants for varied situations. Asarum canadense, Tiarella cordifolia and Chrysogonum virginianum fit this criteria for virtually any landscape and are often the most recommended for gardeners easing into native species in the home landscape.
Some find them to be so helpful in expanding landscapes that they keep nursery beds specifically to provide stock from which to draw quantities on short notice.
Common characteristics among them is a relatively low habit - generally less than a foot high - and steady but not aggressive spreading. All three are easy to divide and transplant at virtually any time of year, although the usual counsel on spring and fall division is best.
All three flourish in open shade, prefer a moist humusy soil that develops from shredded leaves, have shallow root systems to thrive in difficult locations, and offer value to native as well as traditional ornamental design schemes.
Asarum canadense
Asarum canadense (wild ginger) is a good choice for deep shade, when a velvety-green groundcover is the best design choice over species (including shade grasses) that would struggle, or very aggressive introduced ornamentals like ivy or Japanese pachysandra, or slabs of uninteresting mulch.
Individual plants produce a pair of large heart-shaped leaves, all rising four to eight inches from a dense network of rhizomes that intertwine just below the soil surface. Individual plants spread to form colonies, generally doubling in size annually.
The methodical but not frenetic rate of spread permits landscapers to manage the shape and scope of the use, simply by periodically slicing off and transplanting new growth along the edges.
A. canadense is pure groundcover. Plants produce a solitary, not showy, purplish-brown flower hidden under the leaf canopy in spring at the crotch of the two leaf stalks, to be pollinated by ground insects and eventually produce seed that is harvested by ants.
Just a few plants scattered in a deep shade area steadily fill out to form a solid groundcover
In the wild, A. canadense is common in the rich floor of deciduous - rarely coniferous - forests, throughout most of the eastern United States and Canada. In cultivation, a well-drained soil with pH less than 6.8, constantly moist, is all that is required. Light mulching in early spring with shredded leaves is helpful to enhance the soil and hold moisture. It appears on a number of lists of deer resistant plants, but experience indicates that such is not the case.
Propagation by division is straightforward: use a sharp spade to cut through the rhizomes at 6 to 8 inch intervals and immediately transplant and water well, or slice off pieces from the margins. While spring or fall is best, division at any time is reasonable just as long as the transplant is well shaded and well watered for a few days' recovery.
A. canadense will be the first signal that the soil is becoming too dry when leaves begin to droop. Water immediately and they recover within a few hours.
The species gets its common name from use by early Americans as a spice similar to the unrelated real ginger (Zingiber officinale), and it was popular with Native Americans for a broad range of medicinal, culinary and spiritual purposes.
The cheery little blossoms of Goldenstar are continuous from early spring until late autumn.
Chrysogonum virginianum
At the opposite end of the shade spectrum, Chrysogonum virginianum (most commonly known as goldenstar, but also green-and-gold and golden knee), thrives best in light shade with perhaps even periods of gentle sunshine. While it will grow in full shade, the reward of almost continuous bloom from early spring to very late autumn is strongest in slightly better light.
Goldenstar thrives as an edge plant where just a bit of morning sun trickles in.
The leaf mat is 3 to 4 inches, but flowering stems bring the total plant height to nearly a foot. The species is highly variable, even in the shape of the daisy-like bright yellow flowers. C. virginianum expands via rhizomes to clumps approximately 12 inches in diameter from a shallow root system that prefers a well drained, moist to dry - even wet - soil in partial to dappled shade, making it an excellent candidate for populating shady rain gardens. It is a strong choice for dry, sandy soils.
Like all in this group, C. virginianum has a variety of landscape applications ranging from masses as a ground cover to edges along border fronts, or as specimen plantings in rock gardens.
In the wild, C. virginianum populations are rare in Pennsylvania (it is listed as an endangered species) and most commonly found in south central areas of the state. Its native range extends from New York to South Carolina and west to Kentucky (also endangered), Ohio and Tennessee, where it is considered threatened.
In the landscape, removing spent flower stems will provide the best ground cover appearance and the species requires little maintenance; some report that it seems to thrive on neglect.
The "fuzzy" nature of leaves and stems has prompted some authorities to include C. virginianum on lists of deer resistant plants; experiment with excess stock to be sure.
Propagation from seed is uneven. Nutlets mature two to three weeks after the yellow ray flowers fade and drop; harvest when the heads have darkened and store the seed in sealed, refrigerated containers. Seed sown when the soil reaches 70 degrees will germinate. Propagation by division is much easier, with the best success coming from slicing clumps and transplanting in spring or fall, but the species is durable and clumps can be moved at any time.
Foamflower gets its name from the frothy glow of massed plants blooming in May.
Tiarella cordifolia
In between is the enormous popular Tiarella cordifolia (foamflower), a clump-forming perennial that spreads more rapidly than Asarum canadense or Chrysogonum virginianum but which is still relatively well behaved and a spectacular bloomer in springtime. Rather than rhizomes, T. cordifolia advances via stolons, similar to strawberries, setting up a new plant at regular intervals.
This trait makes foamflower an ideal groundcover on either flat ground or in rocky terrain and its ability to withstand brief dry periods makes it exceptionally easy to divide and transplant.
The stoloniferous character of Foamflower is illustrated as a runner tumbles down over an old stone wall, looking for a spot to launch a fresh clump.
As a member of the saxifrage family, Tiarella cordifolia (foamflower) is also reputed by several authorities as "deer resistant," but that remains to be firmly proven and can vary with the neighborhood.
Common in moist, cool, rocky deciduous slopes and stream banks from Nova Scotia, along the entire Appalachian chain into Alabama and westward into Minnesota, it is sometimes found in wet hollows and mossy places, occasionally associated with cedar and hemlock but more often in deciduous forest.
Clumps often range from 12 to 24 inches in diameter, but given a clear path T. cordifolia will fill entire hillsides with maple-like foliage 9 to 12 inches high. In spring (generally mid-May in the Poconos) it produces many 6 to 12 inch racemes of pink buds that burst into a frothy white display of tiny flowers, hence the common name.
Seeds follow bloom in about a month, from the bottom to the top of the raceme, and can be cold stratified for several months before germinating at 85 degrees F by day/60 degrees F by night. Division is far easier, however, and plant vigor will improve with dividing every two years. Divisions can be potted and kept in a greenhouse or cold frame until the following spring, but the plant is so hardy that divisions can often be successfully field planted immediately if well mulched and watered.
Simple bedding boxes can be constructed from pressure-treated lumber, in this case, materials recovered from the demolition of a deck. Permanent boxes should be built with galvanized nails, but temporary units can be held in place with construction stakes.
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Ideal home landscape for T. cordifolia is part shade to dappled shade in moist, humus-rich loamy soil with a pH less than 6.8. While it prefers moisture-retentive soils and should not dry out, wet soils, especially in winter can be fatal. With good mulch of shredded leaves, foamflower can withstand extended dry periods.
Leaves turn reddish to bronze and collapse to the ground in winter and continue a sad appearance until just before the plant springs to life with new shoots in May. Within days, it greens up and launches its flower stalks.
The entire plant has a history of use in folk medicine, especially as a diuretic. The species is rich in tannin, which may be the medicinally active ingredient.
Building stock beds
Species like Tiarella cordifolia, Chrysogonum virginianum and Asarum canadense are active spreaders and helpful in a variety of landscape circumstances. To create simple nursery beds for a continuing supply of stock, assemble shallow boxes from pressure-treated materials (2x6 is ideal). Build one for each of the three species. Select a shady level location, preferably in dappled shade, safe from herbivores and slightly sink them into a layer of coarse sand or light gravel. Fill with a sandy-humusy mix several inches deep.
The three species together form an interesting mass of color and texture when used with introduced ornamentals, such as hosta
At wide intervals in the boxes, plant just a few divisions from purchased plants. Keep the box lightly mulched with shredded leaves, and occasionally water if it gets too dry.
The plants in the box will immediately begin to spread and soon fill the container - providing an endless source of young plants to cull and use in the landscape for sweeping edges, large pools of groundcover or accents in rock gardens.
When a good supply is available, several plants can be tested for deer interest by planting them in triangles, several feet apart. Deer will often test one to determine edibility, but if they leave the others alone, you have an opportunity for broader landscaping. If they repeatedly chew all three, confine the landscape to within a fenced area.