When to plant Lungwort 'Sissinghurst White'?

Pulmonaria 'Sissinghurst White' thrives in partial or full shade, making it ideal for woodland-style borders, beneath deciduous trees, or on the north side of walls and fences. It tolerates loam and clay soils well, provided they retain moisture without becoming waterlogged. Before planting, dig over the soil to a spade's depth and incorporate plenty of organic matter—well-rotted compost or leaf mould—to improve structure and moisture retention, especially important on heavier clay. Plant in March, April, September, or October. Autumn planting is often preferable because cooler, damper conditions help roots establish before winter, but spring planting works well if you keep plants watered through any dry spells. Dig a hole slightly larger than the root ball, set the crown at soil level (not buried), and firm in gently. Space plants 35 cm apart; they will spread steadily to form attractive clumps 30–45 cm wide. Water thoroughly after planting to settle soil around the roots and eliminate air pockets. Apply a 5 cm layer of organic mulch—bark chips, leaf mould, or garden compost—around (but not touching) the crown to conserve moisture, suppress weeds, and mimic the plant's natural woodland-floor habitat. Pulmonaria dislikes drying out, so keep the soil consistently moist during the first growing season. Staking is unnecessary; the low, clump-forming habit of this perennial is naturally self-supporting. Avoid planting in full sun or exposed, dry positions, where foliage will scorch and growth will be stunted.