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. 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. These plants are wonderful in containers, where their blossoms can be enjoyed from up close. 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 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 zones A1-A3, 1-9 and 14-17. To find your zone, click here: Zone Map.

Polygonatum arisanense (Arison Solomon's Seal)
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.

Polygonatum biflorum (Smooth Solomon's Seal, Great Solomon's Seal, 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 pop in March through June, and are followed by small blue berries.

Polygonatum x hybridum (Garden Solomon's Seal)
This species is a cross between Polygonatum multiflorum and Polygonatum odoratum. It is more vigorous than its parent species, and reaches about 3 feet tall when mature. In springtime, clusters of lightly scented small white flowers with green tips appear. Varieties include 'Striatum' (with cream-edged leaves) and 'Betberg' (with new dark brown leaves that mature to green, to 4 feet tall).

Polygonatum multiflorum (Solomon's Seal, David's Harp, Ladder-To-Heaven, Eurasian 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)
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. Variety 'Variegatum' (pictured) has white-edged leaves and dark red immature stems, and 'Flore Pleno' has double white flowers.

Caring for Polygonatum

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.

Propagation

I gather the ripe berries of Giant Solomon’s Seal (Polygonatum biflorum var. commutatum) around mid-September. The seeds contained inside are double-dormant, requiring two winter cold periods before germination. It may take up to several years before maturity and flowering depending on the species and the conditions. While the seeds are probably tolerant of some drying, I always sow immediately or store in a soil mixture for later sowing.