Gardening in the Dry Tropics with Australian Tropical Plants

This article is extracted form the Yuruga Newsletter
Vol 12 No 2
(May 2004).

The focus of this article is for gardeners in tropical Australia.
However, the basic principles apply for throughout Australia
with minor modifications for local conditions.

Yururga Nursery, as most of you know, is located at Walkamin on the Atherton Tablelands west of Cairns. The Tablelands are generally thought of as being lush, green and, because of the altitude, reasonably cool. However, the Atherton Tablelands offer a huge variety of climates within only a short distance, ranging from cool and wet on the southern Tablelands to hot and dry on the northern end.

Yuruga Nursery is situated on the northern end of the Tablelands, and our climate could best be describe as the “dry tropics”. So, this is our story of establishing the Yuruga native gardens in the hot, dry tropics…

Introduction:

Our property consists of 32 hectares of natural bush-land located at the end of an old lava flow, and overlooking the town of Mareeba in the northern distance. We purchased the property in 1979 when we were teachers at the local schools, but eventually our love of native plants took a complete grip of our lives, and in 1985 we established Yuruga Nursery which we have dedicated to the growing of Australian tropical plants.

The gardens, house and nursery occupy about 10 hectares along the top of a steep ridge, skirting around natural springs and swamps, tumbling over piles of basalt boulders, and nestled against the natural open eucalypt forest. On a clear day we have views to the mountains behind the Daintree region 100 km to the north.

Our annual rainfall is approximately 800mm per annum, with the bulk of this falling between December and March. For the remainder of the year it is hot and dry, with bright blue skies, low humidity and high evaporation. Even in our cooler months we very rarely don a jumper, and we never get frost.

An overview:

Our gardens are totally native, consisting exclusively of tropical Australian plants, most of which are from north Queensland and Cape York Peninsula, with a few from the top end of the Northern Territory and the odd couple from the Kimberley region of WA.

While we garden for the delight and joy that plants bring, the gardens also perform a variety of important functions relating to our lifestyle and the operation of the nursery.

Our gardens are essential windbreaks to protect us and the nursery from the strong south-easterlies that blow during the dry season. The gardens modify our harsh ‘dry tropics’ environment by providing shade from the tropical heat and burning sun, cooling the surrounds and capturing welcome humidity. They provide habitat for a great array of birds and butterflies, lizards, frogs, possums, bats, wallabies and other mammals, and some snakes.

The gardens also have established populations of various predatory insects and mites which, together with the birds, play an important part in the Integrated Pest Management programme of the nursery.

The gardens, of course, provide us with an important source of propagating material for the nursery, as well as being a pleasant place for the public to wander and observe the plants we sell in the nursery in their mature form.

Lastly, the gardens are strategically placed around the nursery to provide protection in case of cyclones.

Garden establishment:

Probably the most important issue with gardening in the dry tropics is the fact that there is virtually no rainfall for at least 8 months of the year. In this situation, watering could become a constant nightmare. So, we set out from the start to establish our gardens in such a way that they required as little watering as possible, and we have achieved this with remarkable success. In fact, we water only a couple of times during the dry season, which is far less than most people in more temperate, kinder climates!

  • Soil preparation:
    Our secret boils down to thorough soil preparation, and the use of lavish quantities of mulch on top of the garden beds. We deep-rip our garden beds with a machine such as a dozer or back-hoe prior to planting. This allows the roots of the plants to penetrate deep down into the soil, thus giving the plants the ability to seek out adequate water to sustain them through dry periods. It also ensures that the plants have large root systems which anchor them firmly in the ground and enable them to withstand strong winds and cyclones.
  • Mulch:
    Mulch is absolutely essential in the tropics to insulate the soil against the heat of the baking sun and, of course, to minimise evaporation. Being in a rural area, we are lucky to have access to large quantities of affordable material such as mulching hay, sugar cane mulch, and peanut shell. We use whatever we can get hold of at a reasonable price.
  • Fertilising:
    Unlike a lot of people, we do not believe in applying fertiliser to our plants at the time of planting. For a start, our plants have long-life fertiliser in the potting mix and this is enough to sustain them for the first few months. But also, we have seen a lot of people kill their plants by poisoning them with an accidental overdose. Little plants, like babies, don’t need much food anyway.
    We do, however, believe quite passionately in fertilising our established gardens. The drenching rains of the tropical wet season leach the soil of valuable nutrients, and our older gardens can look quite tired. This is where amazing results can be achieved with a bucket of fertiliser. We use Incitec CK 77S which we buy in 50kg bags from our local rural supplier, and we broadcast it through our gardens as though we are feeding the chooks. This is a very cost-effective way of fertilising large gardens. This particular fertiliser has a low phosphorous content so it is quite safe for natives, a good amount of nitrogen to make the plants green up, and a nice dose of potassium which gives a real glow to the plants. Within three weeks of fertilising our gardens they are rejuvenated, vibrant and full of colour again.
  • Garden beds:
    We always plant our plants in groups in garden beds, about 1.5 m apart. We find that plants nearly always grow better when they are in the company of others, and it is much easier to look after groups of plants compared with scattered individuals. Garden beds nearly always have a greater aesthetic appeal and a more natural look than individuals, and we use sweeping curves to entice people to wander further to see what’s around the corner.

The gardens:

We have never done an actual stock-take, but we think we have about a thousand different species represented in our gardens. In the tropics this is not actually all that difficult to achieve, as the tropical rainforests contain a mind-boggling array of diversity of flora.

For instance, at a quick count we have at least 20 species of native palms, including various Archontophoenix, Licualas, Ptychospermas, Livistonas, Carpentaria, Normanbya, Hydriastele, Wodyetia, Caryota, and even some Calamus . Although we do have a small palm garden planted specially to illustrate the different species, we tend to scatter the palms in appropriate spots throughout our main gardens so as to achieve a natural look. We quite detest the formal rows of palms that are so often planted in landscapes to signify the ‘tropical look’, because they usually look so artificial and jarring.

When we create a new garden we always ensure that it has a backbone of hardy, tried and trusted plants to create the general structure and to provide a solid backdrop against which to showcase the spectacular or unusual. For this reason, the rainforest Myrtaceae are a prominent feature of our gardens, with a big variety of species of Syzygium, Acmena, Acmenosperma, Waterhousea, Austromyrtus and Xanthostemon scattered throughout.

All our gardens also incorporate lots of plants to attract birds and butterflies, such as native rainforest Lauraceae to attract the Blue Triangle butterfly and fruit-eating birds, the beautiful Cape Plum Flacourtia sp and Brown Birch Scolopia braunii to attract the Australian Rustic butterfly, and in the tropics no garden is complete without Melicope elleryana and Melicope rubra (formerly Evodiella muelleri) to attract the stunning Ulysses butterfly.

The rainforest Proteaceae are very beautiful tropical plants, but unfortunately our climate at Walkamin is too dry to grow all but the hardy species such as Grevillea baileyana, Grevillea hilliana, Buckinghamia celsissima and Stenocarpus sinuatus. So as not to miss out, though, we have created a small courtyard which we water regularly so that we can grow and admire some of the more fussy Proteaceae such as Carnarvonia montana, Placospermum coriaceum and Neorites kevediana, and other exquisitely beautiful rainforest plants such as Sarcotoechia serrata, Syzygium erythrocalyx and Acmena sp E. Normanby R. (now Syzygium monimioides).

While rainforest plants form the great bulk of our gardens, we also have lots of tropical grevilleas, callistemons, melaleucas and leptospermums to provide nectar to attract the honeyeaters and flowers for our vases. Grevilleas and callistemons in particular are grouped together in special gardens so that we can provide the full sun and good drainage essential to growing them well in the tropics.