How to grow salvias

Salvias are one of those amazingly diverse groups that make you wonder how such variety can exist among plants of the same name. From hardy herbaceous perennials to tender bedding plants, the herb sage and vibrant shrubs, their unifying feature is brightly coloured, nectar-rich flowers, which bees love.

Which? Gardening magazine grew a range of popular varieties, both hardy and tender types, to see which would give us the best display and be hardy enough to get through UK winters.

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Key facts

PLANT TYPE Herbaceous perennial

POSITION Full sun

SOIL Well-drained, not too fertile

How to grow salvias: month by month

Best salvia varieties

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How we test tender salvias

We grew 24 varieties of tender, half-hardy and borderline-hardy salvias. Many were supplied as plug plants, which we grew on to a larger size before planting out. We planted three of each variety at our Capel Manor trial garden in north London in early summer. Here, the soil is very well-drained and in full sun, although the bed we used has some shelter from a nearby hedge. We kept the salvias well watered until they were established, and then only watered them during very hot, dry weather. We put supports in place only if the plants started to flop. We assessed them until the first frosts hit in early November, and then left them in the ground over winter so we could see which would survive and regrow the following spring.

How we test hardy salvias

We planted three of each variety at our Capel Manor Gardens trial site in north London, where the soil is well-drained and the climate is mild, and three at Logan Botanic Garden in Dumfries and Galloway, where the soil is heavier and the climate cool and often wet. Plants were assessed regularly for impact and duration of flowering;  whether leaves were aromatic; attraction for pollinating insects; and whether they survived the winter. Records were kept for both years, but results irelate to the second year when plants were mature. All plants were deadheaded to see how well they re-flowered.

Caring for your plants

Planting tender salvias

If buying plug plants, pot them up into 9cm pots and grow them in a frost-free place until the roots reach the sides before planting out. Plant out into well-drained soil in a sunny spot. Avoid frost pockets and exposed, windy areas of the garden. Plant in late spring or early summer, after the danger of frosts has passed. Plants bought late in the season (August or September) would be best kept in a frost-free place over winter and planted the following year. If planting into containers, use a Best Buy compost for containers.

Planting hardy salvias

Planting in spring is best, so plants have time to establish fully before the winter. Plant in full sun or light shade. Salvias need good drainage, especially in winter, so plant in well-drained soil.

Propagating

Take cuttings in August or September to overwinter your plants indoors in a light, frost-free place. 

Caring for hardy salvias

There’s no need to feed plants grown in the ground as they thrive in poor soil. If growing in a pot, add a Best Buy controlled-release fertiliser at planting time. Regular deadheading can prolong the flowering period, but watch how your salvia grows. Some will re-flower freely from side shoots and only need to have dead heads snipped off, while others flower in flushes so can be trimmed back with shears when flowers fade. Late-summer flowers can be left on the plants over winter, and cut back when new shoots appear in spring.

Hardiness of tender salvias

All our plants were left unprotected in the ground over winter. We had several frosty spells in the first half of winter with temperatures down to -5°C, but it was otherwise mild and unusually dry. All the smaller, shrubby varieties were hardy – many were still in leaf at Christmas– as was S. uliginosa. None of the three ‘Wishes’ series or S. patens ‘Cambridge Blue’ survived. Shrubby varieties (S. microphylla and S. x jamensis) are often described as hardy, although always with the caveat that they need well-drained soil and sun.

If you aren’t sure your conditions are suitable, you could move your plants undercover in late autumn. If you want to leave them in the ground, either take cuttings in August to September and keep them frost-free overwinter, or protect your plants.

To protect them, cover them with fleece, mulching the crown or lifting the tubers of S. patens varieties. The shrubby varieties will probably lose their leaves and should be trimmed when they start to regrow in late spring or early summer. Long-stemmed salvias regrow from the base, so leave the top growth to die and then cut it back when regrowth starts and frosts have finished.

Common growing problems

Slugs and snails

Slugs and snails may eat young growth in spring so protect your plants with organic slug pellets or use biological-control nematodes (slugs only).

Read more about slugs and snails

Powdery mildew

Powdery mildew can be a problem, especially on very dry soil. A white fungal bloom appears on the surface of the leaf. Remove affected leaves, water plants if the soil is very dry and try to avoid too much overcrowding around the plants to allow the air to move freely.

Read more about powdery mildew