Salvia superstars
The large and beautiful easy-care salvia family has a species or variety to suit any garden. No wonder sales have taken off in the past few years!
Easy-care flower power for any garden
geoff Genge received quite a shock when he recently counted the number of salvia varieties he sells at Marshwood, the perennial nursery he started just over 30 years ago in Invercargill. “I counted 199 different salvias,” he says. “I didn’t think I had so many. Some are common types, some are not.” Then again, as the holder of one of two registered national salvia collections (the other is at the Auckland Botanic Gardens), it’s not surprising that Geoff has quite a few growing at Marshwood.
It was Geoff’s wife Adair who encouraged him to start growing salvia back in the 1980s. “She was the president of our local herb society at that time. Different members of the Herb Federation of New Zealand had volunteered to start national collections of specific plant families such as alliums, thyme and so forth. My wife chose salvia. I don’t know why,” he recalls. “We had a lifestyle block of five hectares back then. I started propagating salvia although I didn’t know anything about them. I slowly built up the nursery and eventually gave up work to run it. It’s still a small one-man band business. My wife helps out occasionally.“
The Marshwood collection is just a drop in the bucket when you consider the genus comprises around 900 species and their thousands of varieties and hybrids. Among that number are shrubs, annuals and herbaceous perennials from many parts of the world including Mexico, California, the Mediterranean region, Central and South America, northern and central Russia, central Europe, Africa and Asia. This extensive geographical spread, the variety of forms and number of species give the genus an incredible diversity, which of course is one of the reasons why salvias are so appealing to plant enthusiasts and gardeners around the world – there’s a species or variety to suit any garden.
Another equally important reason for the popularity of salvia is the ability of many to produce spikes of tubular flowers in intense, jewel-like colours for long periods. These flowers are often highly attractive to pollinators while deer and rabbits will often leave them alone. Add their fast growth rate and generally easy care nature into the mix, and you’ve got a very exceptional and desirable group of plants.
Certainly gardeners seem to think so with salvia sales really taking off in the last few years, says Geoff. “I think people are seeing them in gardening magazines more now. When a plant is mentioned on TV, for instance by Monty Don (on Gardeners’ World in the UK) or in one of the magazines, people see it and want it.”
Salvia genus
Salvia is part of the mint (Mentheae) family. This is most obvious when you consider the aromatic qualities of common or cooking sage ( Salvia officinalis) and the biennial or short-lived perennial clary sage ( Salvia sclarea), used for culinary and medicinal purposes.
It’s not easy to categorise ornamental salvias, though, as there are so many – and opinions seem to vary on how best to do this. In the National Reference Collection at the Auckland Botanic Gardens (ABG), most of the salvias on display have been selected for their ability to do well in Auckland conditions, says senior gardener Mere Brewer. “Those from the Americas (California and Mexico) and South Africa grow well in Auckland.”
The geographical spread of salvias, the variety of forms and number of species give the genus an incredible diversity, which is one reason for salvia’s appeal around the world.
As with all plants, knowing where salvias grow naturally will give you some clues as to the conditions they prefer.
Specialist salvia nurseries such as Dysons Nurseries in Britain group them according to a particular region with sub-categories based on growth habit (shrubby, hardy herbaceous, half-hardy herbaceous and so forth). Dysons specialises in New World salvia from Mexico, Central and South America as well as the southernmost states of the US, and sells some of the more interesting new salvia varieties.
Geoff feels that regional categories are useful but at Marshwood, he prefers to group them according to where they grow best in the garden: their height, sun tolerance and soil preferences. “The thing is not to get too technical,” he explains. What salvias to grow? Nevertheless, as with all plants, knowing where they grow naturally will give you some clues as to the conditions they prefer. If you want drought-tolerant salvias, go for those from Mexico, the Mediterranean or Central America for instance.
If you have a cool, shady garden where frosts aren’t severe, a largeleafed winter-flowering salvia such as the tall Salvia wagneriana would be a good bet. Many of these salvias come from rainforests in the mountains of South America where their flowering is triggered by cool temperatures and short daylight hours – hence winterflowering in our gardens.
Most salvias in New Zealand are summer- and autumn-flowering, and perennial, either herbaceous or shrubby. Some, like Salvia splendens,
Salvia farinacea and their many varieties, are usually grown as annual bedding plants providing bold colour during spring, summer and autumn.
Geoff says that his customers seem to favour the Salvia nemorosa types such as ‘East Friesland’, ‘Blue Hills’ and ‘Caradonna’. Although he doesn’t breed salvias, he’s always interested in new varieties or hybrids that occur naturally. “We keep a careful eye out when the birds and bees propagate salvia and produce interesting seedlings. We’ll pick these up and grow them,” he says. “The best one of these is called ‘Southern Belle’, a hybrid from a Turkish salvia and cooking sage. Cooking sage is actually an excellent garden plant; it flowers for a long time and looks good. We have some planted by the washing line because we heard that Greek women used to throw their washing onto the plants to add their scent. I suspect that would only work well in a hot climate!”
Geoff’s personal favourites are varieties of gentian sage, Salvia patens. This Mexican salvia is prized for its large blue blooms, their colour often described as one of the purest in the plant world. It’s a tuberous perennial that needs to be lifted in colder areas. “A nice one I have seen recently is ‘Amistad’. It has a beautiful purple flower, is tall growing and blooms for months. It looks lovely with tall heliopsis or helenium.”
ABG’s Mere Brewer is also a fan of Salvia patens, particularly the deep blue flowers of ‘Guanajuato’. Another favourite is Salvia nemorosa and its cultivars. “Its flowers come in shades of violet, purple, white or pink. It’s clump-forming and flowers in early summer to autumn. Cut back hard after the first flush of flower and it will have a second flush.”
Mere’s also recommends the woody clumping ‘Indigo Spires’ and autumnflowering Salvia madrensis. “This is a tall, herbaceous variety with spikes of long yellow flowers and is suitable for a large garden at the back of the border,” says Mere.
Salvia leucantha and Salvia leucantha ‘Purple Form’ are evergreen clumping salvias that flower in summer until the frost slows them down. Mere explains that you only need one plant as they grow about 1m x 1m. Divide after three years for more plants.
You can create new plants by dividing clumps in spring, which should be done every three to four years anyway for herbaceous salvia.
Salvia care
Many salvias tolerate frost and hot sun although some winter-flowering types need to be sheltered from both.
Well-drained soil is essential for most, advises Geoff. “However some salvias can cope with more moisture, like bog sage ( Salvia uliginosa). Most need sun, but again some like semi-shade especially the Chinese, Taiwanese and Japanese salvias such as Salvia nipponica. They also like dampness at their feet. Working out the best conditions for salvia really depends on the region where they originated.”
When asked about pests and diseases that affect salvias, he can’t name one. At the ABG, Mere says that aphids can be a problem with smaller salvia in autumn. “But we just cut them back and leave them alone.”
Pruning is generally considered essential for most salvias to encourage more flowers and keep plants in shape. When to cut them back depends again on the type of salvia and where you live. At Marshwood, autumn-flowering salvias coming into flower can be hit hard by frosts, says Geoff. “But if frosted down to the roots, don’t cut them back or you risk losing the plant. Leave the dead foliage and stem until spring when it will come away again from the base.”
Most salvia should be pruned back by a third after flowering to encourage a second flush of blooms. With shrubby salvia, some growers give them a mild prune in autumn (particularly in colder areas) followed by a more severe cut back in late winter or early spring. They argue that leaving a little more growth during the winter can help plants cope better with the cold. No matter when you prune remember that cutting back too severely leaving no stems can also shock salvia plants and kill them.
For deciduous herbaceous salvia with soft stems such as Salvia elegans,
Salvia guaranitica and Salvia leucantha varieties, old growth will die down through winter, and new leaves and stems emerge from the base of the plant. However, you’ll get more flowers and plants will look tidier if you cut them back twice a year, first in spring when new shoots start to appear at the base and then again in late summer or autumn.
When cutting back your salvia in autumn, it’s a good idea to feed them with organic matter or a general fertiliser, and mulch plants to provide nourishment through winter. Give them a thin layer of compost in spring and cover with more mulch to retain moisture and reduce weeds.
Propagating salvia
You can create new plants by dividing clumps, which should be done every three to four years anyway for herbaceous salvia. This is best done in spring as new growth emerges.
For shrubby salvia, take 10-12cm hardwood cuttings, cutting through just below a node, in winter (spring or summer in colder areas). You can also take tip cuttings of soft new salvia growth earlier in the year.
Trim off lower leaves and push them directly into the ground (for hardwood cuttings) or into pots with a mix of potting compost, perlite, vermiculite or sharp sand.
As well as being a straightforward process, propagating salvia from cuttings rather than seed also means new plants will be true to form. But if you don’t mind the risk (or the fun!) of cross-pollination, sow in spring and autumn directly on top of the soil and water. Just beware salvia seed can have a short viability.