If the current heatwave in Sydney has any messages, one of them for me it is that using warm-climate plants in our gardens makes more and more sense. In high summer, Sydney gardens can show their semi-tropical side, if filled with plants that thrive in the heat. The plants keep right on growing through the hot months, and can make the garden look so full and exuberant at this time of year. Before I added these plants to my garden, it was fairly bereft of colour in summer; I now rejoice in their glowing jewelled hues amidst luxuriant foliage. Our hot (and getting hotter!) summers enable us to grow a wide range of subtropical annuals, perennials, vines, shrubs and trees which are too tender or which sulk in cooler climates but which flourish in our warmest weather, usually continuing blooming well into autumn.
In my own garden, I never embraced a completely full-on tropical style garden with palms, cordylines, banana trees and other dramatic foliage plants, but sought instead warm-climate flowering shrubs and shrubby perennials to create my own peculiar version of English herbaceous borders with colour, texture and a profusion of flowers over as long a period of time as I could manage. Decorative warm-climate foliage plants are added into the mix for dramatic effect, and semi-tropical annuals self-seed in gaps to provide ribbons of bloom amongst the other plants.
Dahlia and Canna provide brilliantly coloured flowers for months on end, in a rainbow of hues. Both come in a range of heights, with compact specimens suited for smaller spaces or pots. Other good performers include a number of summer-flowering Salvia shrubs: probably the most floriferous being 'Amistad', with its seemingly endless array of spires of rich purple flowers. Smaller salvias such as those from the 'Mesa' and 'Heatwave' ranges also bloom well for months on end, in an array of colours.
A stalwart small shrub that sails through the hottest weather is Pentas. A rounded plant up to about 1 m in height, it is covered in posies of tiny star-shaped flowers in colours of pinks, purples, mauve, white and red. A number of Acanthaceae plants are also in bloom throughout the hottest months: the shrimp plant (Justicia brandegeeana), with quirky inflorescences of crimson, rusty-red or lime-yellow; the so-called white shrimp plant (Justicia betonica), with its upright white spires, looking very good at the moment; Justicia carnea, with its chubby pink or white plumes; Brillantaisia subulugurica, with its striking panicles of purplish-blue, claw-like flowers; and Pachystachys lutea, with its golden candelabra blooms. All of these shrubs will grow in part-shade as well as sun.
In recent times, I have been growing a Hawaiian-type hibiscus (Hibiscus rosa-sinensis) successfully for the first time, and it is melding in well with the rest of my semi-tropical plants, and producing opulent, pastel-pink flowers each with a deep red maroon that add an exotic flavour to the garden. It is possibly the cultivar 'Apple Blossom'. Another plant I am pleased with is Mussaenda frondosa, a plump, wide shrub 2-3 m tall bedecked with small orange flowers with large, attractive white bracts that look like bunting draped through its branches. It looks effective in a border with white flowers and white-variegated foliage plants. There are cultivars with other coloured bracts, such as pink and red, but they seem to need milder winters than we experience in Sydney. Other tropical-looking shrubs I grow include the angel trumpet (Brugmansia) and Lepechinia salvae with its arrow-shaped foliage and spikes of raspberry-hued flowers.
Coloured foliage lends itself to creating an exuberant semi-tropical-style look, and amongst my favourites are Iresine, which has forms in hues of cerise, purplish-brown and yellow-striped green; and coleus, with myriad variations of colour and pattern. My current pet has brilliant orange leaves, pairing nicely with a delightful dwarf Canna with neon-orange blooms. Some of the Canna themselves have decorative colours on their bold, paddle-like foliage, such as the yellow-veined 'Striata'; and striped orange, red, green and bronze in the popular 'Tropicanna'. A yellow-variegated leaf ornamental ginger (Alpinia zerumbut 'Variegata'), has stunning yellow/green variegated foliage (ht 1.5 m). It is an excellent plant to bring light and colour into gloomy parts of the garden; it also is in flower now, with trusses of creamy-coloured, waxy buds opening to reveal yellow and red shell-like blooms. The metallic purple leaves of Strobilanthes dyeriana and the velvety silver foliage of Plectranthus argentatus are also favourites for stunning leaves.
Warm-climate, self-seeding annuals that have found a place in my summer garden include the brilliant blue Browallia americana, the burgundy-tasselled Amaranthus caudatus, tall, airy Verbena bonariensis, the brilliant orange-apricot bracts of Euphorbia cyathophora and lime-green Nicotiana langsdorffii. I do pull hundreds of seedlings up when they appear, just leaving a few here and there, otherwise my garden would be overrun!
I relish the lush - almost rampant - growth of these plants at this time of year, when it can be a battle to walk down garden paths with jungle-like foliage blocking the way, and the blowsy explosion of flowers that is so very, very different from springtime! To grow to their full potential, these sorts of plants need humus-rich soil and sufficient moisture. After my horrendous water bill last summer, I am relying on my drip irrigation system this year, assisted by applications of a soil-wetting agent and plenty of mulch. So far, the plants are holding up OK, despite the terrible heat of this past week in Sydney. Regular deadheading keeps the flowers blooming: and that's about the limit of gardening for me right now, whilst the heat is forecast to go on ... (but thank goodness for a cool respite this weekend just past!)
Creative pest control
25 Oct 20
There are lots of ways to outwit garden pests!
18 Oct 20
Although my garden is semi-tropical in nature now, I still have some vestiges from my cottage garden days!
11 Oct 20
Consider training a shrub into a small tree.
04 Oct 20
October is iris time in Sydney gardens: the best are the tall bearded irises and Louisiana irises.
One crowded hour
27 Sep 20
Much can be achieved in regular short stints in the garden.