Description of Hypericum grandiflorum (Large-flowered St John's-wort)

Hypericum grandiflorum is a large-flowered St John’s wort grown for yellow blooms and tidy foliage. It’s a useful plant for damp ground that is not permanently flooded. In a bog garden, it fits best on the higher, slightly drier areas.

Appearance

It forms a low shrub-like clump with narrow leaves and bright yellow flowers in summer. Flowers are open and flat with prominent stamens. In good conditions it can sit around 60 to 90cm tall and wide, with a long flowering run.

Care Guide

It likes light, air, and steady moisture. Soggy crowns can cause problems, so place it where water drains slowly rather than sits deep.

• Sun: Full sun to part shade.
• Soil: Moist, reasonably fertile soil that doesn’t stay stagnant.
• Water: Damp soil suits it. Water in dry spells on the upper bog edge.
• Pruning: Cut back lightly in spring to keep it compact.
• Feeding: A spring mulch of compost supports flowering.

If stems get leggy, a harder spring cut encourages fresh shoots from lower down.

Suitability for Bog Garden

This works in bog gardens as a bridge plant between wet and normal borders. Use it on the upper edge where soil stays moist but not waterlogged.

It pairs well with rushes and irises because the flower shape is simple and the foliage stays neat. In smaller beds, keep it away from the wettest centre so the crown doesn’t sit in deep saturated compost all year.

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