Polygonatum

( pol - ig - oh - NAY - tum )

At-A-Glance Information

Commonly called King Solomon's Seal or just Solomon's Seal, this genus is filled with woodland plants that need partial to full shade and regular water to perform well. These plants slowly spread via rhizomes and send up arching stems with green leaves. In spring or early summer, pairs or clusters of white-green flowers bloom and hang underneath the stems. They have a fragrance that is reminiscent of Lily and Hyacinth. Berries will sometimes follow flowers, and they are bluish-black in color. Leaves and stems will yellow before the entire plant dies to the ground in fall. Use these flowers as groundcover, to naturalize in woodland landscapes, or in shady mixed beds and borders as accents. Take care when planting these in the garden, as they are toxic to humans and pets if ingested.

Polygonatum Species and Varietals

The genus Polygonatum is a member of the plant family Asparagaceae and includes around 63 distinct species. The plants in this genus are closely related to those in Maianthemum (False Solomon's Seal), Convallaria (Lily-of-the-Valley), Ruscus (Butcher's Broom), and Aspidistra (Cast Iron Plant). The genus name is derived from the Ancient Greek word for 'many knees', referring to the multiple-jointed rhizome roots. Solomon's Seal grows best in USDA hardiness zones 3-9 or Sunset growing zones A1-A3, 1-9 and 14-17. To find your zone, click here: Zone Map.

Polygonatum arisanense (Arison Solomon's Seal, Solomon's Seal, 阿里山黃精, Alishan Huangjing, 阿里黃精, Ali Huangjing)
This species, native to Taiwan, grows in the Alishan Range around 1,500 meters in elevation. Flowers are white and bloom in spring and summertime. Blooms are followed by small berries. Individual plants in this species reach up to 3.3 to 6.5 feet tall when mature and in bloom.

Polygonatum biflorum (Smooth Solomon's Seal, Great Solomon's Seal, Solomon's Seal, Small Solomon's Seal)
This species, native to the eastern and central regions of North America, reaches 1-3 feet tall and 2 feet wide, with white flowers held in groups of two or three. Blooms are present in March through June and are followed by small blue berries.

Polygonatum x hybridum (Garden Solomon's Seal, Hybrid Solomon's Seal, Solomon's Seal)
This group of cultivars is a result of crosses between Polygonatum multiflorum and Polygonatum odoratum. Plants more vigorous than their parent species and reach about 3 feet tall when mature. In springtime, clusters of lightly scented small white flowers with green tips appear. Cultivars include 'Striatum' (with cream-edged leaves) and 'Betberg' (dark brown leaves mature to green, to 4 feet tall).

Polygonatum multiflorum (Solomon's Seal, David's Harp, Ladder-To-Heaven, Eurasian Solomon's Seal, Common Solomon's Seal)
This species is native to Europe and temperate Asia, and reaches 35 inches tall and 10 inches wide. Flowers are pendulous, tubular, and white. Cultivar 'Variegatum' has cream to white-variegated foliage.

Polygonatum odoratum (Polygonatum japonicum, Polygonatum officinale) (Angular Solomon's Seal, Scented Solomon's Seal, Fragrant Solomon's Seal)
This species is native to Europe and Asia and reaches 1.5-3.5 feet tall and 2 feet wide, with fragrant flowers that usually bloom in pairs. Cultivars include 'Variegatum' (pictured) with white-edged leaves and dark red immature stems, and 'Flore Pleno' with double white flowers.

Caring for Polygonatum

Take care when planting these in the garden, as they are toxic to humans and pets if ingested. Polygonatum, or Solomon's Seal, does well in full to partial shade. They are naturally woodland plants, and appreciate a similar environment. When grown in areas with cooler climates, they can have a bit more sun exposure. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 5.0 and 7.0 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, Solomon's Seal plants appreciate moist soil, but do not do well in standing water. They can tolerate short periods of drought, but will begin to wilt and drop flowers if left in dry soil for too long.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders (as long as soil is relatively rich in nutrients), and this feeding should be sufficient to provide the necessary fuel for the active growing and flowering seasons. Prune off dead, damaged, or diseased stems at any time by cutting them back to the base of the plant. Remove spent flower stems to discourage reseeding and clean up appearance. This also encourages more blooms to emerge. These plants do not need any heavy pruning; after the flowering season ends in fall, foliage will die back and can be removed. Solomon's Seal overwinters as an underground storage root, which can be protected with a layer of mulch. Foliage and flowers will regrow in the spring. In early spring, plants can be divided if needed. A good rule of thumb for determining whether plants need dividing is if they are not flowering or otherwise performing well. For instructions on how to successfully divide Polygonatum, see the Propagation section below. These plants can survive in the landscape for decades before needing to be replaced, and will form clumps over time that can be divided and replanted elsewhere, providing plants for the garden indefinitely.

Propagation

Polygonatum, or Solomon's Seal, plants are most commonly propagated via division of rhizome roots. They can also be propagated via seed. To propagate your plant, follow the instructions below:

Propagating Polygonatum by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil, compost and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every 2 to 3 years regardless of whether you have the goal of propagating the plants for best performance, especially if they are being cultivated in containers. To propagate by division, follow these steps:

Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the rhizome(s). Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick, healthy root section attached to above-ground growth.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, replant your bulbs and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout in the next growing season.

Propagating Polygonatum by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a container, a pot or tray, potting medium, and a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds in fall. Polygonatum seeds are located inside berry-like fruits. Take care when working with fruits, as they are toxic. They will turn dark blue, black or red (depending on the species grown) when they are mature. Remove them from the plant and cut them open. Take out the pulp and seeds, and then run them under cold water in a sieve to remove extra flesh from the seeds.
Polygonatum seeds will need a period of cold-stratification in order to germinate. To complete this process, first place seeds in a bag or other sealable container filled with moistened sand or peat moss. Then, place the container in the refrigerator (or similarly cool, dark space) for 2-3 months. The ideal temperature for cold-stratification is around 40 degrees Fahrenheit. After this period has passed, remove seeds from the container.
Get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them lightly with soil and water with a spray bottle. Place the sown seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 30 to 90 days from sowing. If seeds are not germinating, another round of cold stratification may be required.
Keep the seedling's potting medium moist, but not wet. Keep your seedling in an area with bright light and temperatures between 65 and 75 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when the seedling can be hardened off and then planted outdoors.