Polygonatum × hybridum 'Betberg' is a Solomon's seal selection grown as much for its stems as its flowers: new shoots emerge a deep, near-black purple in spring, and the young leaves carry that same dark flush along their margins before gradually fading to plain green as the arching stems mature through summer. Paired, pendulous white bells with green tips hang beneath the stems in the same season, typical of the genus, but it's the dark spring color that sets this cultivar apart from a plain species Solomon's seal.
Culture is identical to any Polygonatum: rich, consistently moist, humus-heavy woodland soil in partial to full shade, where it spreads slowly by rhizome into an increasingly full colony over years without ever becoming aggressive. It tolerates drier shade once established, though the display is best with reliable moisture. Solomon's seal sawfly larvae can strip a colony's foliage rapidly in early summer if left unchecked, and are the main pest to watch for — otherwise this is a low-maintenance, long-lived shade perennial that needs little beyond leaving it alone.
Botrytis (grey mould)
Grey fuzzy mould on petals and stems, worst in cool wet conditions.
Remove affected parts immediately. Improve air circulation. Avoid overhead watering. Apply copper fungicide if severe.
Rust
Orange to brown raised pustules on the undersides of leaves, with yellow spotting on the upper surface. Heavy infections cause leaves to yellow and drop.
Remove and destroy infected leaves. Avoid overhead watering and improve air circulation. Apply a sulfur or copper-based fungicide if it spreads. Clear plant debris in fall.
Fungal leaf spot
Brown or purplish spots on the leaves, often ringed with a yellow halo, that spread and merge in warm, humid, or wet weather; heavily spotted leaves yellow and drop early.
Pick off spotted leaves and clear fallen debris to remove overwintering spores. Improve air circulation by thinning, and water at the base so foliage dries quickly. If it persists, apply a copper- or sulfur-based fungicide at the first sign.
Solomon's Seal Sawfly
Phymatocera aterrima →Grey-white larvae with dark heads feed on leaf undersides, stripping foliage to bare midribs and leaving stems skeletonized by midsummer.
Inspect leaf undersides from late spring and remove larvae by hand. Knock larvae into soapy water or apply spinosad if infestation is heavy. Plants usually recover the following year even after full defoliation.