Solomon’s Seal: An Old-Fashioned Perennial Worth Rediscovering

Smooth Solomon’s seal (Polygonatum biflorum). Photo: haraldmuc, depositphotos

With its gracefully arching stems and its ability to tolerate even the darkest corners, Solomon’s seal belies the belief that nothing worth growing is adapted to shade.

By Larry Hodgson

This old-fashioned beauty is found in many older gardens. However, it has been somewhat overlooked in the wake of the new plant introductions flooding the gardening market over the last decades. That said, it’s certainly a perennial worth rediscovering! After all, what can you have against a plant that:

• Lives forever (there are specimens well over one hundred years old in historic gardens!);
• Requires no care;
• Is attractive from spring through fall;
• Will grow in even the deepest shade?

Overview

There are some 70 species of Solomon’s seal (Polygonatum), a genus in the Asparagaceae family. Most of the common varieties share same basic shape: stems that grow upright at first, then arch gracefully to one side as they continue their growth. This creates a most attractive and intriguing effect. The arching stems bear broad lanceolate leaves on opposite sides of the stem, like a ladder. The effect is doubly charming in the fall when the whole plant turns golden yellow. The fact is, Solomon’s seals are mainly grown for their leaves and their charming habit.

The flowers and fruits, although not uninteresting, mostly serve to add to the appeal of the stems and leaves. The blooms, borne singly or in groups of 2 or more, are usually elongated creamy-white bells with a green tip. They dangle from thin pedicels below the stems. The plant’s own leaves partially hide them from view, though. Unless you plant your Solomon’s seal on a slope at eye level or higher, they can be a bit discrete. I find that their little game of hide and seek simply reinforces the oriental appearance of the plant. They’re like a shy geisha who half hides her face behind a fan.

The flowers are followed by green fruits turning black or very dark blue (more rarely red). They remain on the plant until the foliage turns yellow in the fall.

The name “Solomon’s Seal” derives from its fleshy creeping rhizome. It’s marked with round dark depressions as if a seal had been pressed into it. And the name Polygonatum also comes from the gnarled rhizomes, because it means “with multiple knees.” Unless you dig up a plant and wash off its roots, though, it’s not something you’re likely to see.

Many species of Solomon’s seals were used as medicinal plants in their native lands, but are rarely used medicinally today. Two generations or so ago, they were common garden perennials. That’s why they are so often found in abandoned flower beds around old houses. 

Not many people realize that the rhizomes and stems of several species are edible after cooking. The fruits, though, are slightly toxic. They rarely cause poisoning, though, as you would have to eat large quantities of them to make yourself sick.

Taxonomic Confusion Reigns! 

You’ll have no trouble finding Solomon’s seals in nurseries. Most carry at least one variety. What is less certain is whether the accompanying label bears the correct name. If ever a plant needed a “paternity test,” it would be the Solomons’s seal! Many species have such a similar appearance that even experts have a hard time putting the right name on them.

If you find a small, green leafed Solomon’s seal in a nursery, at least in North America, it’s probably smooth Solomon’s seal (Polygonatum biflorum). Theoretically, it is about 1 ½ to 3 feet (45 to 90 cm) in height. However, taxonomists recently repatriated other larger Solomon’s seals under this name. That most notably includes great Solomon’s seal, now P. biflorum giganteum (it was formerly known as P. commutatum). It often reaches over 6 feet (2 m) in height! So, if your plant is either specially small or particularly tall, it probably belongs to this species.

Note that the botanical epithet, biflorum. It suggests that the greenish-yellow flowers are grouped by twos at the leaf axils. However, that’s not always the case. Smooth Solomon’s seal can just as easily have three or four flowers per axils as two. And most other species too have a variable number of flowers per leaf axil.

Smooth Solomon’s seal is a North American native, widely distributed in most areas east of the Rocky Mountains. Hardiness zones: 3 to 8.

Hybrid Solomon’s seal (P. × hybridum) is another commonly available variety. At 3 to 4 feet (90 to 120 cm) tall, it’s of medium height for a Solomon’s seal. It’s a natural hybrid between P. multiflorum and P. odoratum, and is native to Europe. Most of the green-leaved varieties sold under the names P. multiflorum and P. commutatum probably belong to this species. It is probably the most widely cultivated medium-height Solomon’s seal, although it’s rarely sold under its true name. Hardiness zones: 3 to 8.

Often offered for sale, most plants labeled as scented Solomon’s seal or angular Solomon’s seal (P. odoratum) actually belong to the previous species. But you do sometimes find this Solomon’s seal in nurseries that specialize in shade plants. What gives its identity away is that its green-tipped white flowers, in groups of 1 to 4, are fragrant. This is especially true in the evening. If your Solomon’s seal isn’t scented, then it isn’t P. odoratum, no matter what the label says. Another defining trait: the stems of the fragrant Solomon’s seal are angular rather than tubular. 

It produces nearly black berries. Due to its short rhizomes, tends to be less invasive than some Solomon’s seals. It is widely distributed in Europe in the wild and is one of the smaller Solomon’s seals at about 2 to 3 feet (60 to 90 cm) in height. Hardiness zones: 3 to 8.

Another Solomon’s seal native to North America is hairy Solomon’s seal (P. pubescens). It’s about 1 to 3 feet (30 to 90 cm) tall and looks a lot like smooth Solomon’s seal (P. biflorum). It also shares most of its range with that species, although hairy Solomon’s seal tends to be more eastern in its distribution whereas smooth Solomon’s seal is more central. You need to do a touch test to tell these two plants apart. The underside of the leaf of hairy Solomon’s seals are somewhat fuzzy. Smooth Solomon’s seal leaves are devoid of hair. 

Look for green or greenish-yellow flowers and blue-black berries. Hardiness zones: 3 to 8.

There are also double-flowered varieties of several of the species described above.

Varieties with Colorful Foliage

Several species of Solomon’s seal have produced cultivars with variegated foliage. Two varieties in particular are common on the market (and often confused). 

Variegated fragrant Solomon’s seal (P. odoratum ‘Variegatum’) bears leaves with thin white margins. It’s about 18 to 24 in (45 to 60 cm) in height. It was named Perennial of the Year in 2013 by the Perennial Plant Association, which greatly boosted its popularity. It has since become the most widely available Solomon’s seal in many areas.

Variegated hybrid Solomon’s seal (P. × hybridum ‘Striatum’ or P. × hybridum ‘Variegatum’) is the same size, but its leaves are not only edged, but also streaked with white. 

Either variety will create a superb effect in the shade, where the white lines of their leaves really stand out.

There are also several other variegated Solomon’s Seals, mostly newer and more expensive cultivars with even more striking variegation than the traditional varieties. This group includes P. × hybridum ‘Grace Barker’, with highly variegated and somewhat contorted leaves, and P. odoratum plurifolium ’Double Stuff’, well variegated with a contrasting red stem. There is even a variety with whose foliage is purple in the spring: P. × hybridum ‘Betberg’.

All plants described under Varieties with colorful foliage grow very well in hardiness zones 3 through 8.

Upright Solomon’s Seals 

While the typical Solomon’s seal has a clearly arching stem, there are several upright forms. While certainly available, most of them are relatively unknown.

I particularly like dwarf Solomon’s seal (P. humile), only 5 to 9 in (12 to 23 cm) tall, which is perfectly erect. It bears attractively ribbed leaves on either side of its short stem. At the end of spring, a flower or two dangles down from the upper leaf axils. The blooms are creamy white with a green tip. The fruits are blue-black. It’s an excellent ground cover, forming a dense carpet. Really, this is a plant that deserves to be much more popular. Hardiness zones: 4 to 8.

There are also taller upright Solomon’s seals, such as the whorled Solomon’s seal (P. verticillatum). Its erect non-arching stems bear long narrow leaves, almost like needles. They are set all around the stem in groups of 4 to 8. As a result, it almost looks like an abnormally airy horsetail (Equisetum)!

Also, this species forms dense clumps over time and is in no way invasive. Tiny rather insignificant flowers, white with a green tip, appear in groups of 3 to 8. They turn into red berries at first, but eventually turn dark purple. Some clones are fairly short: 1 foot (30 cm). However, those that are commercially available tend to be tall: about 5 feet (150 cm). Hardiness zones 5 to 9.

The Siberian Solomon’s seal (P. sibiricum) closely resembles whorled Solomon’s seal, but is hardier: hardiness zones 3 to 8. It reaches 4 to 5 ft (120 to 150 cm) in height.

The Perfect Choice for Shade

Solomon’s seal is basically a shade plant, thriving in situations so dark that hardly anything else can grow. It can even tolerate competition from tree roots, although this slows down its already very slow growth. That doesn’t mean that it won’t grow in the sun. However, plants grown in full sun may have somewhat washed out foliage. And may also need watering while shade-grown plants rarely need any. Shade and partial shade suit Solomon’s seals better.

This plant is used to dealing with “difficult situations,” for example, very heavy soils or soils filled with tree roots. For that reason, there is no need to pamper it with rich, arable soil: any soil will do. Likewise, in the wild this woodland plant gets along fine with leaf litter (decaying fall leaves) as its sole source of fertilizer. If you naturalize it in a forest, therefore, then you won’t really have to fertilize it. In a more controlled landscape, you could use an organic mulch to replicate the leaf mulch. It will fertilize the soil as it decomposes.

Although tolerant of both drought and flooding, Solomon’s seal prefers moderately moist soil. If you are planting it under shallow rooted trees, where summer drought will be a factor, try this. Dig a planting hole as deep as the root ball, but 3 times its diameter. Then line it with 5 to 7 sheets of newspaper. The paper acts as a temporary barrier against tree roots. That will give the plant the chance to settle in before the roots return. Water your Solomon’s seal well the first two summers to make sure it can become established. Afterwards, the tree roots will no longer bother it.

Solomon’s seal is at its most attractive when allowed to form a large clump, but it also grows very, very slowly. If you don’t want to wait 5 or 6 years for it to start creating that kind of effect, it may be worth planting 4 to 7 specimens together. Set them about 8 to 12 in (20 to 30 cm) apart to create the effect of a clump from the start.

Its very slow growth doesn’t mean that the Solomon’s seal can’t be invasive. On the contrary, once established, many species will grow steadily but inexorably outwards. Over time, they might end up taking over more space than you’d like. To counter this “bulldozer” effect, try planting your Solomon’s seal inside a root barrier of some sort. A bucket with the bottom removed would work well. If not, it’s easy enough to dig out the wandering sections. Often, gardeners simply naturalize this plant in woodland garden. There, no harm will come even if the tuft reaches 10 feet (3 m) wide … after 40 years and so!

Easy to Multiply

Once established, the Solomon’s seal offers a profusion of rhizomes. They can be dug up, cut into sections and replanted, preferably in the spring or fall. It’s rarely propagated by seeds, contained in its dark blue berries, because they are so slow to germinate. They sometimes take 3 years before they sprout! And they’re very slow to reach maturity even after that.

Few Enemies

The Solomon’s seal is reputed to be very resistant to insects and diseases and deer and rabbits usually avoid it. Sometimes slugs do poke a few holes in the first leaves of the spring, but nothing too serious. 

One minor enemy is the scarlet lily beetle (Lilioceris lilii), a bright orange insect that normally attacks lilies (Lilium spp.). It isn’t usually attracted Solomon’s seal, but occasionally seems to settle on certain clones of P. biflorum. Usually, the damage is minor, as the plant is not a good host for the beetle and even appears to be mildly poisonous to it. After a few days on Solomon’s seal leaves, the insect stops feeding. Also, it’s unable to reproduce on this host plant. 

If beetles settle on your Solomon’s seal, try sprays with neem oil to get rid of them and keep them at bay. Neem is both an insecticide and a repellant. Or hand pick. You won’t find lily beetles to be very persistent on this plant.

Designing With Solomon’s Seals

The Solomon’s seal is a perfect choice for the woodland garden where it can be naturalized, but also for any shady location. It looks especially attractive in a garden of Asian inspiration: just imagine it in a Japanese garden!

Beautiful Combinations

Solomon’s seals with green leaves will beautifully highlight variegated and yellow hostas (Hosta spp.). Variegated varieties would look great combined with green-leafed woodland plants, such as green hostas, ferns of all kinds, barrenworts (Epimedium spp.) and trilliums (Trillium spp.).

Where to Find Solomon’s Seals?

Pretty much every garden center will offer at least one variety of Solomon’s seal. For a greater choice, you may need to purchase them through mail order. If so, consider nurseries specializing in shade plants, heritage perennials or native plants.

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Solomon’s seals: so much to offer and yet so easy to grow!