Their benefits include:
1. Human health – though the nutritional values of most of Australia’s edible plants are still little appreciated or understood, they undoubtedly possess not only recognised vitamins but also unique values that benefit health in this climate.
2. Garden health – by attracting a range of birds and various pollinators to the garden, they enrich the biodiversity values that are essential to a TRULY sustainable garden
3. Habitat restoration – if you live in Australia native food plants extend the natural vegetation linkages that are so vital to the sustainability of both plantlife and wildlife – how wonderful it would be to create a network of gardens and parks across the country enriched by plants that can feed both wildlife and humans!
4. Good looks – the rainforest species mentioned in this article are all attractive, garden-friendly plants that can be put to a variety of landscape uses – as single ornamentals, in shrubberies and buffer zones, as hedges, pot plants, street trees and feature plants in courtyards.
Here is my selection of the Top Six rainforest plants for food and good garden behavior:
Davidson’s Plum (Davidsonia pruriens)
Riberry (Syzygium luehmanni)
Lemon Myrtle (Backhousia citriodora)
Illawarra Plum (Podocarpus elatus)
Finger lime (Citrus australasica)
Red Bopple Nut (Hicksbeachia pinnatifolia)
You don’t actually need to give these plants any care after establishment; they’ll survive and even thrive. But if you’re growing them for food, a bit of extra TLC will give you more and better fruit.
General cultivation tips: Improve soil at the planting site with compost; provide water in summer dry periods, fertilise young trees for improved yield (but never too much because too much nitrogen can promote foliage growth over fruit production); prune to maintain manageable shape and size; control fruit fly (in the two plums), protect from weather extremes. As many soils are deficient in calcium, it may help to add gypsum. Spring is the best time to fertilise and a high potassium fertiliser will improve fruit development in nut and fruit trees.
Unripe Davidson’s plums growing from the trunk of the tree
The best of the two subspecies being cultivated, because it produces the largest and nicest fruit, is Davidsonia puriens var. puriens (the other is Davidsonia puriens var. jerseyana). This tree occurs naturally in northern New South Wales and tropical/sub-tropical Queensland. It’s quite small – to about 8m – with attractive toothed foliage and colourful new growth. Fruits can be as large as 6cm in diameter and are purplish black with reddish flesh. Very juicy but not very palatable because rather sour, so best if stewed with lots of sugar or honey. A dash of port or brandy does wonders to the flavour! The plum makes excellent jam and wine, and is a useful extender in other fruit jams. Fruit is produced mostly in summer (though sometimes both earlier and later) and in mature trees is very prolific. Improved yield cultivars are now available.
Cultivation: To improve fruit yield, cultivate the planting area by digging it over. Add plenty of compost. Plant in a position protected from wind and frost. Light shade is best, though a position with direct morning sun will help boost fruit production and flavour. It doesn’t like too much competition from other trees nearby – this slows growth. Davidsonia has a high moisture requirement; like most south-east Queensland rainforest plants it can withstand long dry periods but will grow faster if water can be provided during drought. Beetles may defoliate the tree from time to time but it soon recovers – a much worse problem is fruit fly, so take whatever measures you prefer for this pest and pick fruit when still fairly green, so it can ripen indoors. Ripe fruit stores in the frig and the pulp can be frozen
Propagation: Fresh seed germinates easily. Early growth is slow.
Riberry (Syzygium leuhmannii)
Above: This is actually the fruit of Syzygium australe, closely related to the riberry and very similar in taste and texture
This ornamental lilly pilly bears lots of small, pear-shaped, pinkish-red fruits in summer. It’s a big tree to 30 m and can be widespreading too, so needs lots of room. It’s also fast-growing – the more water it has the faster it grows! It bears at an early age compared with most rainforest trees – about five years depending on conditions. When mature it’s very prolific. The crisp, tart fruit is edible though not exciting. It makes a very good juice when boiled with a sugar syrup and also jam, sauce (like cranberry sauce) and chutney, either alone or with other fruit (choco and riberry chutney is good!). I add it to fruit salads, or any type of salad, and use in a variety of dishes – curries, stir-fries, as a garnish. Also with apple and other fruit in pies.
Cultivation: Using cutting-grown stock and pruning regularly means you can keep this to a manageable shrub size – it makes an excellent hedge but DOES need frequent trimming. It’s not fussy about soil and will take temperatures down to zero – and can even recover from frost, though protection when young is advisable. Plant in sun or shade, though full sun means more and better fruit. Improved (composted) soil will mean better fruit production and water retention, and maintaining an acidity level of around 5.6pH will assist nutrient take-up if you are fertilising your plants. Mulch well. I’ve found that good drainage is essential for healthy riberries and at the same time they like a lot of water (but not waterlogging). They’re geared naturally to withstand dry periods in winter/spring but growth will slow or stop if this happens during summer – so water may need to be applied. Fertilise with a low-phosphorus formula in spring, when the temperature begins to rise and rainfall begins. This is only necessary in the first couple of years to encourage growth. I just use compost and it seems to work well. Some commercial producers fertilise again in autumn.
Prune young plants to encourage a multi-stemmed growth (up to 4); then again lightly each year after fruiting (more if it’s a hedge but remember heavy pruning will prevent a good fruit crop next time because fruit develops on each year’s mature growth). If the tree grows too large, it will need a good cut back every few years, and this will be followed by reduced fruit production for the next few seasons.
If you’re planting a hedge, seedlings should be about 2m apart – if planting an avenue of individual trees/shrubs space about 5m apart – depending on desired size at maturity. Don’t plant too near drains, swimming pools or any buildings.
The worst problem is a borer that gets into the ripening fruit. I don’t know a sustainable remedy for this – I’d try standard non-chemical remedies as for other fruit. Monitoring is crucial, and fruit should be picked immediately it ripens. Scale and sooty mould can also be a problem – natural oil remedies are the best remedy.
Improved varieties – for size, flavor and seed reduction – are available. Fruit stores quite well and can be frozen. Fresh seed propagates quite easily but cutting-grown improved varieties are best.
A wonderful plant; every garden should have one because it’s beautiful, easy to grow, useful and versatile. The leaves are the richest source of cineole in the world and useful as a biocide, should you want to go to the trouble of extracting the oil. It has a real “lemonade” flavour that’s not as harsh as other lemon-flavoured plants and is particularly suited to Asian dishes. It’s also easier to grow, better-suited to predominantly warm and wet climates and not so prone to insect attack as lemon verbena or lemon balm. (But try growing your lemon myrtles with a lemon balm groundcover for a REAL lemony experience!) Some claim that planting this small tree in and especially around a food/herb garden keeps certain pests at bay – even if this is not valid, lemon myrtle makes an excellent ornamental herbal hedge plant if kept trimmed low and bushy. Use for anything in which you need a lemon flavor – it makes good lemonade if leaves are boiled with sugar and water; can be used for lemon-flavoured oil or vinegar; makes a delightfully fragrant tea and is perfect with fish – or in a gin and tonic! The leaf dries well.
Cultivation: No need to do much except perhaps provide water during very long dry periods in summer. Tip prune regularly and trim lightly once a year in autumn to maintain a manageable shape and height – keep it as a shrub rather than a tree. Protect young plants from wind. Grow in shade or full sun; sunlight develops the leaf flavour. This is a decorative landscaping plant for feature shrub/tree, border planting, hedge, tub or courtyard.
Illawarra Plum (Podocarpus elatus)
This striking tree is a member of an ancient family of conifers that take us back to Gondwana. Though slender when young, it can grow pretty tall and wide. In autumn and winter female trees produce a blue-black fruit to about 30mm diameter with the seed carried on the outside of the flesh at the opposite end to the stem. The fruit can be stewed like Davidson’s Plum, or used with other fruits to make jam, chutney and sauces. It tolerates most local soil conditions including alkaline (though it occurs naturally on acid soils), and is also tolerant of light frosts.
Cultivation: As for Davidsonia but again don’t overdose with high nitrogen fertiliser after the first year or two (when you need to encourage growth). Apply in early summer, rather than spring. This tree is a bit slow to start but gets away after the first 2 – 3 years. It needs plenty of water during establishment and again during long, dry periods in summer. As always, prune lightly after fruiting and tip prune after that to promote bushiness and keep size small.
This is a tough plant that can be used for buffer plantings and is also a good timber tree. You need to have at least one male plus a couple of female trees for pollination and fruit production. Best to look for plants from good nurseries that clone their superior selections.
Finger Lime (Citrus australasica) and Wild (or Round) Lime (Citrus australis)
Finger limes grow as small, shrubby trees in Queensland coastal ranges and lowand forests. In summer and autumn (usually) they bear finger-shaped fruit up to 10cm long, with thin green or yellow skin and green-yellow pulp. A subspecies with pink to red-flesh and red to purple or even black skin (Citrus australasica var. sanguinea) also exists but is becoming very rare. The grafted cultivar “Rainforest Pink Pearl”, now popular in cultivation, is bred from this – and is probably the best bet for home gardens because those from the wild take too long to bear – anything from 5 to 17 years!
The fruits make excellent marmalade, drinks and tangy sauces, and can be used alone or with other fruits including as an extender with exotic citrus. They are delicious if pickled whole in brandy or any other liquor, like cumquats.
The Round Lime occurs on the margins of rainforests and tolerates drier conditions. Its fruit is round and looks rather like a small exotic lime, with a thick green-to-yellow skin and pale green pulp.
Australian native limes are hardy trees and rather slow growing, especially at first – but well worth the effort because they are both tasty and ornamental.
Cultivation: Like all citrus they bear best if given water, especially in dry periods. A formulated citrus fertiliser seems to work well, applied in spring. Or just use a rich compost with plenty of potash added, for fruit development. Prune lightly in winter to open up trees and maintain height to no more than 4m.
Red Bopple Nut ( Hicksbeachia pinnatifolia)
This tree bears a really tasty nut rather like a macadamia. It’s oval and bright red on the outside, containing an almond-sized kernel. Tree height is about 8m and can be kept smaller by light pruning; or made to develop several trunks if pruned when young (as with riberry). Seed germinates easily but seedlings need quite a bit of care so buying plants from a rainforest nursery is the easier option. Plant in spring/summer only and give protection from wind.
Cultivation: As for Davidsonia and macadamias.