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Plant care

Smooth Solomon's Seal (King Solomon's seal) care

Polygonatum biflorum

Also called Smooth Solomon's seal, King Solomon's seal, Small Solomon's seal.

RHS H7USDA 3-8Mildly toxic to petsIndoor 30–120 cm tall (1–4 ft)

Watering rhythm

Medium indirect light (a couple of metres from a window)

Regular; keep soil evenly moist

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Light

Medium indirect light (a couple of metres from a window)

Soil

Fertile, humus-rich, moist but well-drained

Humidity

Moderate

Temp

-35 to 30°C

Pet safety

Mildly toxic to pets

Mature size

30–120 cm tall (1–4 ft)

Care at a glance

Light

Smooth Solomon's Seal wants the spot a few feet back from a sunny window — bright enough to read a paperback at noon, but the sun never falls directly on the leaves. Best in part shade to deep shade; performs well beneath deciduous trees where it receives morning light or dappled sun throughout the day. A faint hand shadow at midday is the right amount; a sharp dark shadow means it's getting direct sun and probably too much.

Watering

Water smooth solomon's seal regular; keep soil evenly moist. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Water freely during dry periods, especially in the first season; once established it tolerates dry shade better than most woodland perennials, but consistent moisture produces the best growth.

Soil and pot

Smooth Solomon's Seal grows best in fertile, humus-rich, moist but well-drained. Thrives in any reasonable woodland soil enriched with leaf mould; tolerates clay if drainage is adequate and handles a range of pH from slightly acid to mildly alkaline. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Smooth Solomon's Seal sits happiest at around Moderate humidity and -35 to 30°C (-31 to 86°F). Suited to the ambient humidity of temperate woodland gardens; no special provision needed when grown in its preferred shaded, moist site. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed smooth solomon's seal sparingly. Top-dress with well-rotted compost or leaf mould in spring; avoid high-nitrogen feeds that promote soft, disease-prone growth. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on smooth solomon's seal in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Solomon's seal sawfly (Phymatocera aterrima) — Grey-green larvae strip leaves to the midrib in late spring and early summer; inspect stems regularly from late May onwards and remove larvae by hand or treat with a contact insecticide.
  • Powdery mildew — In dry, warm summers, powdery mildew can coat the upper leaf surface with white powder; improve air circulation, maintain soil moisture, and remove badly affected foliage.

Propagation

Divide rhizomes in autumn or early spring; replant 2–5 cm deep and 30 cm apart. Seed is slow to germinate and requires a cold stratification period of several months. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Smooth Solomon's Seal is mildly toxic to pets. Contains steroidal saponins throughout; the ASPCA classifies closely related Polygonatum odoratum as mildly toxic to cats and dogs, with clinical signs including vomiting, diarrhoea, and drooling. Berries may additionally contain cardiotoxic compounds. Keep pets away from all plant parts. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Smooth Solomon's Seal care — frequently asked questions

What is the common name for Polygonatum biflorum?

Polygonatum biflorum is most commonly called Smooth Solomon's Seal, but it is also known as Smooth Solomon's seal, King Solomon's seal, Small Solomon's seal. The names refer to the same species, so care instructions for Smooth Solomon's Seal apply identically to anything sold as King Solomon's seal.

How much light does smooth solomon's seal need?

Smooth Solomon's Seal grows best in medium indirect light (a couple of metres from a window). Best in part shade to deep shade; performs well beneath deciduous trees where it receives morning light or dappled sun throughout the day.

How often should I water smooth solomon's seal?

Water smooth solomon's seal regular; keep soil evenly moist. Water freely during dry periods, especially in the first season; once established it tolerates dry shade better than most woodland perennials, but consistent moisture produces the best growth. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is smooth solomon's seal toxic to cats and dogs?

Smooth Solomon's Seal is mildly toxic to pets. Contains steroidal saponins throughout; the ASPCA classifies closely related Polygonatum odoratum as mildly toxic to cats and dogs, with clinical signs including vomiting, diarrhoea, and drooling. Berries may additionally contain cardiotoxic compounds. Keep pets away from all plant parts.

What USDA hardiness zone does smooth solomon's seal grow in?

Smooth Solomon's Seal is rated for USDA zone 3-8 and RHS hardiness H7. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Smooth Solomon's Seal deep-dive guides

Every aspect of smooth solomon's seal care, each with its own calibrated guide:

Featured in these plant shortlists

Smooth Solomon's Seal qualifies for 4 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Smooth Solomon's Seal is also known as Smooth Solomon's seal, King Solomon's seal, and Small Solomon's seal.