It’s high summer in the subtropics and one of my favourite groups of tropical perennial plants are in full bloom: Meet the Zingiberales. This is a botanical order to which belong eight botanical families with a shared evolutionary ancestry. Every gardener is familiar with some members of the Zingiberales, you’re likely to find examples of six of these families in every street and garden centre in Queensland. You may even know their families are related. Plant a few and your garden can have its own source of attractively shaped, delightfully coloured and sometimes fragrant cut flowers and foliage.
Starting with bananas, this family contains some of largest and most leafy of the Zingiberales. They are classified as the Musaceae, the banana family. Once you can imagine their form in your minds eye – the paddle-shaped leaves and terminal inflorescences (flowers at the end of stems), it’s easy to recognise another allied botanical family – the Cannaceae, or cannas, a favourite of warm climate parks and gardens. In cool temperate England, lush, leafy, colourful cannas are treated with a greater respect than Australia. I used to have them bedded out in parks and gardens to flower during summer. You cut them down after the first frost, lift and hold the over winter in trays of soil, keeping them dry without desiccating them in a frost-free glasshouse for replanting the following summer.
Next, look to the Strelitziaceae, which includes the bird-of-paradise, Strelitzia reginae. This family has with tougher, more drought-tolerant stems, leaves and flowers than the Musaceae. Bird-of-paradise is so reliable and tolerant of light frost and heat, it is commonly used in park and roadside landscaping. Another iconic plant is the travellers’ palm. Although it originates from Madagascar, this huge plant is grown for its silhouette rather than its flowers in big, warm climate gardens and parks worldwide. When I first visited Singapore, it was decorated as an alternative Christmas tree. When I first visited Queensland, I associated its distinctive silhouette with old timber Queenslander houses in the sugar growing districts.
Four families in the Zingiberales, the Heliconiaceae (heliconias), Zingiberaceae (true gingers), Costaceae (spiral gingers) and Marantaceae (prayer plants) have received much attention by growers and breeders to create a wide range of flower colours and patterned foliage. They still have the same paddle-shaped leaves, but these are produced in great variety and sizes, and some members of the Zingiberaceae are winter herbaceous.
Since most Zingiberales have paddle-shaped leaves, by growing just them you can lose the visual impact, so unless you are farming them for their flowers, it is best to consciously mingle them in a border with plants that have contrasting foliage. Bromeliads, salvias, ferns and cycad not only add a distinctive appeal in their own right but they also enjoy similar growing conditions in terns of sunlight, moisture, exposure and drainage. They’re good companions.
Members of the Zingiberales are distinguishable not just by their terminal inflorescences, but also because these sprout from the tip of a leafy pseudostem (a false stem). The inflorescences consist of a collection of long-lasting, colourful and often very showy bracts that are modified leaves. The supporting pseudostem they sprout from isn’t woody like a shrub, instead it is made up of layers of rolled leaf bases.
All plants have co-evolved with animals. Many member of the Zingiberales specialise in nectar producing flowers to attract bird pollinators. Strelitzia flowers go one step further by offering birds a perch where they can sit and as they sip nectar, their necks get dusted with fresh pollen which they take to pollinate the next flower.
Some animals are so effective at exploiting the leafy Zingiberales they become significant pests. Damage by some moth caterpillars and grasshoppers can spoil a display. Learn to spot moth egg masses and squash them before they hatch. Regularly checking and hand picking can control small outbreaks of caterpillars and juvenile grasshoppers before can reproduce. Spot spraying individual pests using pyrethrum allows the control of pests that are too high to reach. You will have read my social media posts about how to use my grandfather’s molasses recipe to control grasshoppers on soft-leaved crop plants sweetpotato. It can similarly be used on soft-leaved members of the Zingiberaceae and Marantaceae families and is especially beneficial where they are mass planted.
Apart from the Strelitziaceae, which can cope as a roadside planting in poor soil and with natural rainfall, many of the Zingiberales look their best in cultivated conditions sheltered within a fenced garden. The best shade for shade loving members is high shade or dappled shade (think jacaranda), or 4-6 hours of morning sunshine, not all day sunshine or all day shade.
The Marantaceae mostly dwell on protected, damp, leafmould enriched forest floors, which is why they make sterling houseplants. They also look good mass planted as ground covers and complement birds’ nest ferns (Asplenium).
The Zingiberales possess a rhizome, which is a modified underground stem. Some spread noticeably, while others form tight clumps. Depending on the species, it is important to occasionally lift, divide and replant clumps to avoid clumps becoming congested and dying out in the centre. However, with the deep-rooted, tightly clumping Strelitziaceae, it is vital you choose a permanent position with care – established plants will go nowhere without the assistance of a mechanical digger. Do not be tempted to plant them in the ground beside a swimming pool, keep them in containers.
In the tropics, most Heliconia flower and grow more strongly if they are lifted, divided and re-set in their positions every two to three years. In the subtropics, where growth is slower, this can be done once every three or more years. Your prompt to do this is when the clumps die out in the centre, or when they become congested with dead and dying old foliage.
Reinvigorating plants this way provides the gardener more flowers and it multiplies your plants in the process. It also allows you to tidy up their debris and to make compost from it. I have found that the process of digging and resetting these clumping perennials also discourages vermin, like rats, from tunnelling underneath them and breeding.
Feed with a general purpose fertiliser once a season during spring to autumn. Poultry manure is perfect and regular foliage feeding with seaweed covers all their nutritional needs.
Choose fully-developed, well-formed and still closed flowers. Use sharp secateurs or a pruning saw and cut early in the morning when plants are well hydrated.
Once in a display, re-cut the base of the pseudostem daily to keep them capable of taking up water. Change the water daily. You might wish to put a couple of drops of household bleach into each change of water to reduce bacterial growth.
Australia’s ancient tropical and subtropical soils are generally highly leached of nutrients, acidic and lacking in sufficient calcium and magnesium to meet the needs of these plants. Complete a pH test before planting and adjust as necessary. Both reduce soil acidity and lime provides calcium, which is vital for plants health, however, dolomite provides calcium and magnesium. In a new garden, adjust the soil pH as recommended three weeks before planting. Test soil pH once a year in autumn after the wet season has finished and adjust as necessary.
In general, provide Zingiberales with:
* High or dappled shade and shelter from desiccating or cold winds;
* Compost rich, well dug, freely draining soil;
* If you mulch, use soft, leafy mulches such a rice hulls, dried lawn clippings, hay, straw or sugarcane no more than 5cm deep;
* Damp, not wet, conditions during the warm seasons. These plants cope better with relatively dry periods during the cool seasons;
* Feed with a general purpose fertiliser only when they are actively growing;
10th March 2021