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Solomon's Seal

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Oh, my aching muscles...

...lends elegance to the shade garden
By Marty Wingate

Marty's web site

Shade in the garden is in no short supply. If it isn’t shade from evergreens—usually our native Douglas firs (Pseudotsuga menziesii), Western hemlocks (Tsuga heterophylla) and red cedars (Thuja plicata)—then it’s deep shade from nearby buildings. Nature abhors a vacuum—so even in shade—bare soil, left untended, usually fills up with unwanted plants.

Instead of leaving the weeds to their own devices, why not choose some shady characters that appreciate a little relief from the sun and, at the same time, add charm, texture and form to the garden? In the top 10 of any gardener’s list for shade plants such as that should be Polygonatum.

Polygonatum—known as Solomon’s Seal, because the rhizomes are marked with what looks like the official seal of King Solomon—comprises species that are native to North America, Europe and Asia. They grow best in part to full shade.

What draws us to these herbaceous perennials is their elegance in the garden. Tall stems arise singly from underground rhizomes and arch gracefully. Leaves are held on an almost horizontal plane, and the small white flowers, which are bell or tube-shaped and often tipped in green, dangle on delicate stems from leaf axils.

Polygonatum is either a member of the lily family (Liliaceae) or the lily-of-the-valley family (Convallariaceae); it depends on the whether you are a lumper (the former) or a splitter (the latter), taxonomically speaking. You’ll find both family names in current literature, reflecting the fact that plant classification is a lively and ongoing subject.

And speaking of names, several of the Polygonatum species have variable names—for example, is it P. commutatum or P. biflorum var. commutatum? And what about the giant Solomon’s Seal, often listed as P. canaliculatum? Variability in size led to the long-held conclusion that these were different species or at least distinct varieties of the same species.

And variable it is. When described as separate species, P. biflorum is said to grow to about three feet, while P. commutatum can get to seven feet. It’s no wonder these weren’t considered the same. Even so, the latest news is that the various names and groups of plants have all been collected into the species P. biflorum, no matter how variable.

Known as the smooth Solomon’s Seal, P. biflorum is the most common North American native Solomon’s Seal to be found in our gardens. As an American woodland plant, companions come to mind easily—shrubs such as summersweet (Clethra alnifolia) and sweetshrub (Calycanthus floridus) and perennials including the wood aster (Aster divarcatus) and mayapple (Podophyllum peltatum).

Although they grow in humus-rich soil with medium moisture, most Polygonatum, once established, can carry through dry periods in the summer, as long as they are planted in the shade. And a good mulch helps, too.

The species of Solomon’s Seal we are most familiar with in the garden share similar characteristics: unbranched stems; alternate leaves that are almost sessile (that is, almost attached directly to the stem without a leaf stalk) with conspicuous veins that look almost parallel; small, pendant, green-tinged white flowers that vary slightly in number (from one or two to a few) according to species and cultivar.

Similarity in species shouldn’t be used as an excuse to have only one kind of Solomon’s Seal in the garden. They are far too useful for that, and gardeners should consider a collection rather than a single representative, much like we might do with Epimediums (which also make good companions to Solomon’s Seal).

And although size and scale are important to consider, even gardeners with small spaces shouldn’t shun some of the taller-growing selections just because there doesn’t seem to be room. After all, we can’t fill our gardens only with plants labeled ‘Nana’ or ‘Compacta’ or it will look like we live in Lilliput. So, if that P. biflorum you bought grows a few feet taller than you expected—let it rise out of a sea of hellebores. You’ll be the talk of your garden club.

Dark blue berries develop by fall in P. biflorum as well as in P. multiflorum and P. x hybridum (the latter being a cross between the first two). The dark berries stand out against the yellow-gold fall foliage, making the end of the year as decorative as the beginning.

The European species P. multiflorum grows up to two feet and has flowers that often appear only on the bottom half of the stems. The hybrid between these two species—P. x hybridum—is (with typical hybrid vigor) quick to take hold in the garden. Several cultivars of P. x hybridum are listed, but not all are readily available. In literature, there is a double named ‘Flore Pleno’, but searching online and in catalogs resulted in no sources. The equally elusive ‘Nanum’ grows slightly smaller than normal (to about 18 inches). The foliage of ‘Striatum’ (a cultivar that is available) is irregularly edged in creamy white.

The fragrant Polygonatum odoratum ‘Variegatum’ is a beauty. Its dark red stems rise two to four feet, and the horizontal leaves are delicately edged in white. Small white, pendant flowers appear in late spring or early summer, followed by dark blue fruit. A colony of these lovelies in the shade garden lighten any darkness.

The variegated fragrant Solomon’s Seal can be listed as P. odoratum var. thunbergii ‘Variegatum’ or it can be listed as var. pluriflorum. These appear to be the same plant. In the Royal Horticultural Society’s Plant Finder (a great source for tracking down names) there is no thunbergii, only pluriflorum, so it appears to be one of those plants that drift from one name to another for awhile before settling.

Several plants are either quite similar in appearance or near relatives of the Solomon’s Seal, and they all make fine companions. The false Solomon’s Seal (Smilicina racemosa) is a Northwest native; its flowers are a plume of creamy white. There is also evergreen Solomon’s Seal (Disporopsis perneyi), twisted stalk (Streptopus amplexifolius) and fairy bells (Disporum hookeri) (the latter being two more Northwest natives).

More species are being introduced into the gardening world all the time, thanks to intrepid modern-day plant hunters such as Dan Hinkley. These may be harder to find in the trade, but sometimes the hunt is half the fun.

Look for the diminutive groundcover P. hookeri that grows to only three inches high, but spreads out in a carpet. Polygonatum humile is slightly taller—to about six inches. These short species obviously don’t have room to arch their stems as the taller species do. When in bloom, the upright stems of P. humile look like they have a vertical white zipper of bells.

A woodland garden in spring catches at the heart strings. Be sure your woodland garden includes Polygonatum for an effect that charms in spring, but also carries through with stately elegance until the garden rests for the year.

Solomon's Seal has an understated elegance and grace. It's a very charming plant in a shady border.

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