A tall and hardy species, Salvia uliginosa (right) reaches around 1.5m (5ft) and in wetter parts of the country it can even tower up to 1.8m (6ft). It likes to have its feet wet in moisture retentive soil as its common name, bog sage, indicates. Although it is quite tall it is self-supporting and doesn’t require staking due to its stems being naturally wavy and lax in habit. This means it gives great informal height to areas of planting in the garden, either towards the back or as a centre piece. As with all salvias the flowers are ‘two-lipped’ and this species has pale blue-silver flowers that last for a long time during high summer.
The pale tones of its flowers make it easy to combine with many other colours including pastel shades of yellows, pinks and whites, providing a soft contrast. At RHS Garden Hyde Hall Salvia uliginosa can be found in the Hilltop Garden near the oak pergola where it grows alongside yellow-flowered plants such as Kniphofia ‘Early Buttercup’ (left) and Phygelius x rectus ‘Moonraker’.
It is also grown in large drifts near the Entrance Courtyard at RHS Garden Hyde Hall where its wavy stems combine with naturalistic grasses such as Miscanthus which carry the colour and texture into the autumn.
For contrasting foliage try planting Helichrysum petiolare ‘Limelight’ (right) around the base which is a tender plant with soft, lemon yellow foliage. For a complimentary planting scheme try planting Amsonia orientalis with its soft blue flowers or a tender salvia such as Salvia patens ‘Cambridge Blue’.
As with many tall plants, this Salvia can have bare stem bases and to resolve this potential problem, lower growing plants should be planted in front, such as the Phygelius, to hide the stems. Salvia uliginosa is easy to grow and prefers a sunny site but in the right conditions it can be a vigorous perennial and spreads with surface runners which may need controlling each spring to ensure the plant remains where you originally planted it.