Lately I've been admiring some of the most startling blue-flowered salvias in my garden. I think salvias do have some of the most brilliant blue flowers in the plant kingdom. Blue has always been my favourite colour and I sometimes wonder if this is why I became so enchanted with salvias in my younger gardening years, a love that endures to this day. There are salvias of all shades of blue - from pale baby blue, sky-blue, violet-blue, midnight-blue, purple-blue and azure-blue to name just a few, but I particularly adore ones with royal blue flowers (though colour labels are notoriously tricky in themselves and can mean different things to different people!): to me this is the bluest of the blues. So many of the other flowers of this colour - such as delphiniums, gentians, clematis and grape hyacinths - don't thrive well in our Sydney gardens (apart from in the cooler, more elevated suburbs), but salvias do very well!
My obsession with this colour led me to be seduced early on in my gardening journey by a truly wicked salvia: Salvia guaranitica - which sported flowers of this hue. How I loved it! Then (like many other gardeners who had been similarly beguiled), I discovered that it is a rampantly spreading plant, multiplying via large underground tubers that are very hard to get rid of. Eventually, I discovered a version of it known simply as Salvia guaranitica 'Large Form' (ht 1.3 m) and it flowers just as well as the scary one but is definitely non-invasive. It is an excellent long bloomer in my garden, from late spring until early winter. It is pretty with any other flower colour: white, yellow, orange, pink, cerise, lime (such as Nicotiana langsdorffii) as well as lime or gold foliage, either plain or variegated. It is best in full sun, but in hot areas it will enjoy some afternoon shade.
A plant new to me this year is Salvia sagittata 'Mosquito'. It has dainty 'true blue' flowers on black stems, and large, felted, arrow-shaped leaves. It is found in the wild at very high elevations in the Andes. It is frost-sensitive, suggesting it comes from the warmer parts of that region. It grows around 1-1.5 m tall in Sydney and flowers in summer and autumn. It flourishes best in full sun and is really a gorgeous plant, the flowers seeming to float in mid-air above the beautiful foliage.
Salvia sinaloensis is a low-growing plant from Mexico with one of the bluest of all salvia flowers. It spreads by underground runners to form a thick, ground-covering clump (but I don't regard it as invasive). The dainty flowers will soon appear on upright stems (ht 25 cm) and continue on through summer. The leaves can take on purplish tints if grown in full sun, but it does also do well in light shade. It appreciates watering during dry times. It makes a good underplanting for yellow or lime-green blooms, such as those of Kniphofia 'Lime Glow' or Justicia brandegeeana.
Looking beyond salvias, other plants that have brilliant blue flowers in my garden at the moment include Neomarica caerulea, a rhizomatous plant from Brazil with tall, attractive fans of evergreen architectural foliage (ht to 1 m). Its exquisite iris-like flowers, coloured the most brilliant blue, are appearing now (the photo doesn't do justice to their blueness!). Each lasts for but one day but they continue to open over several weeks. The flowers look particularly stunning when paired with nearby cerise blooms, such as those of Canna or Dahlia, or with silvery foliage such as that of Plectranthus argentatus. Neomarica caerulea thrives best in a sunny, well-drained spot with good soil, but is tough once it is established. Another rhizomatous plant that has variants with brilliant blue flowers is the good old Agapanthus, which is just coming into bloom now. The cultivars 'Electric Blue' (ht 75-90 cm) and 'Guilfoyle' (ht 1.5 m) are two I grow with rich blue flowers, but there are many more available these days.
Amongst annual plants in my garden, the most stunning blue flowers perhaps belong to Browallia americana, an easy-to-grow bushy annual from tropical South America (ht 30-60 cm), which has a mass of starry flowers in summer and autumn. It grows best in sun but will tolerate some shade; it grows in most soils. It is rarely seen for sale: if you are able to obtain even a single seedling from the garden of someone who grows it, you will have it forever. I started with one such lone plant given to me by a kind friend, and now have literally hundreds of them coming up each spring. They obligingly fill in any spare spaces in the garden, without swamping surrounding plants. Annual Lobelia erinus is another plant that has lovely rich-blue variants, and I have grown it in a pot recent times.
I'd love to hear about your favourite blue flowers!
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