The first method I employed was the dripper system. An intricate network of dripper lines, filters and flow regulators that feed each individual plant. It was an expensive and labour intensive system that kept the trees alive, but that’s about all it did. Things were alive, but they weren’t strong and healthy. It turns out the biggest problem with drippers is that they supply water to only a very small area, and as a result plants concentrate their roots in only the area that is being kept moist. Think about it this way, if a plant has a regular supply of water close by, why would it bother growing an extensive root system? As a result they become very dependent on regular watering and if you forget to water them they very quickly become stressed and show little resilience. An additional problem is that because they have a small concentrated root system they aren’t very stable and are more likely to fall over during strong wind.

Next I replaced the drippers with an off-the-shelf micro irrigation system – in other words, a variety of fancy sprinkling attachments that sprayed water all over the place. It looked good but the fine spray seemed to be evaporating in the air and the plants were very susceptible to stress if they weren’t watered at least every second day. So after two years the micro system ended up in a box in the shed beside the dripper system.

Nowadays I have a very simple system and only water my garden once every two or three weeks. And believe it or not, my plants are stronger and healthier than they’ve ever been. The key was to encourage plants to develop a strong and deep root system. This has been achieved by using larger sprinklers that produce larger water drops at a much greater volume. These are left running for at least three hours. That way the water penetrates deep into the ground instead of just the top 10 centimetres. As a result plant roots grow over a larger area and grow deeper as they chase the water further down as the surface becomes dry. And due to the now much larger and deeper root system, my plants have improved their hold on the ground and are less likely to fall over during a blow.

Two to three weeks between watering works well for my plants and soil conditions, but how do you know exactly when to water? Simple. Look at your plants when the sun has set. If they look firm and healthy, then their roots are still able to find the water in the soil. If, however, they look limp and tired after the sun has set then they are no longer able to get the water they need and it’s time to give them a good deep soaking again.

Happy gardening.

Marcus Achatz
Yuruga Nursery

(Published in Cairns City Life magazine, May 2008)

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.

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.

Creating a rainforest garden is easy!

There are two secrets to creating a rainforest garden, and no, they are not water, and more water! In fact, water is no more a necessity for a rainforest garden than it is for any other type of garden.

The two secrets are:

1. Dig up the garden bed thoroughly to provide as much loose soil as possible;
2. Provide a thick layer of organic mulch.

Soil Preparation

Rainforest plants, as a general rule, have very timid root systems. Unlike acacias, eucalypts and grevilleas which have robust root systems capable of penetrating hard ground, rainforest plants have timid, shy root systems that tend to stop dead at the first sign of an obstacle. Consequently, rainforest plants planted in hard ground simply will not grow.

Rainforest plants grow best when you garden in the traditional fashion – pretend they’re roses or a vegetable garden, and plant them in a bed of thoroughly loosened soil. The ideal depth is about a foot (30cm). On a small block of land, this means rolling up your sleeves and getting stuck into the ground with the pick, shovel and elbow grease to physically break up the soil. You haven’t finished until your original hard lumpy ground is nice and soft and friable.

If you are planting a large garden, it’s well worthwhile to use a machine – a bobcat or backhoe, or even a small bulldozer with rippers can prepare a large garden bed in a flash. It’s not expensive – for less than one hundred dollars you can prepare a garden bed which would take many days to prepare by hand, and the resulting plant growth will be spectacular to say the least. (See Information Sheet ‘Soil Preparation’)

Mulch

Mulch is absolutely essential to grow rainforest plants well. The mulch should be organic and applied as a thick insulating layer on top of the soil much like a blanket covering a bed.

Thick organic mulch is essential for several reason, including:

• It keeps the soil moist by reducing evaporation
• It controls weed growth
• It keeps the soil cool
• It provides a source of recycled nutrients
• It keeps the soil healthy by maintaining a balanced population of micro-organisms

Unlike most acacias, eucalypts and grevilleas, rainforest plants are very surface rooted. It is therefore essential to keep the surface of the soil cool and moist, otherwise the roots will bake and dry out.

As we said above, rainforest plants have timid roots; give them an obstacle and they give up very easily. If you allow weeds or grass to grow around the base of rainforest plants, they cannot compete.

Weeds and grass will severely inhibit the growth of rainforest plants. A thick application of mulch will keep weeds and grass at bay.

For rainforest plants, it is essential that the mulch be organic, since the recycling of nutrients is very important for their growth.
The type of mulch you choose is not important, so long as it is organic. You can use anything, so long as it was once a plant. In north Queensland, bales of mulching hay are popular. In some areas, peanut shell may be available. Many shire councils sell mulched-up garden waste. Wood chip is fine. Newspapers and cardboard are OK, but it is best to shred them first – if you spread them out in sheets they act as a thatched roof and prevent water penetrating the soil beneath. (See Information Sheet ‘Mulching Your Native Plants’).

Mulch should be applied as a clean blanket on top of the soil surface. It should never be dug into the soil – this is for compost, not mulch.

Things such as black plastic are no substitute for organic mulch. Black plastic does not allow the soil to breathe, and it does not allow the recycling of nutrients that is so important. In warm climates, it can cause the soil to overheat. Don’t use black plastic. If you really think you need to, don’t. Make your layer of organic mulch twice as thick instead.

Watering/humidity

Provided you have a thick layer of organic mulch, you will find that you don’t need to water your rainforest garden any more than a normal garden, although it will love any extra water you can give it. Of course, your rainforest plants must be watered for the first few months until they are established, just like any plant, be it a wattle, grevillea or callistemon. (See Information Sheet ‘Watering Your Native Plants’).

However, rainforest plants as a rule cannot tolerate dry winds. Unlike acacias and eucalypts etc., which have a thick waxy cuticle over their leaves (among other adaptations) to prevent excessive moisture loss in dry times, rainforest plants have little protection against evaporation since they have had no need for it in their natural habitat. It is more important to maintain a reasonable humidity level in the air than it is to apply water to the roots.

To grow some of the more delicate species in drier areas such as Townsville or Mt Garnet, you may need to trap humidity around your plants by planting a shelter belt of hardier species or by creating a courtyard.

Fertiliser

Rainforest plants love to be fertilised – fertiliser brings out the lovely foliage colours that make rainforest plants such a delight to grow.

The rules for fertilising rainforest plants are the same as for ordinary natives – check the N:P:K ratio to make sure the phosphorus is low – less than 3% is best.

Water in well, and don’t overdo it. Like medicine, a little is good for you, an overdose can easily kill. (See Information Sheet ‘Fertilising Native Plants’).

A handy reference to rainforest plants for your garden:
‘Growing Australian Tropical Plants‘ by Radke & Sankowsky

Let’s dispel some of the common myths …

Myth : Rainforest plants need to be planted in the shade.

Wrong! Just because the rainforest is a shady place to walk in, does not mean that rainforest plants need shade. What it means is that rainforest plants cast shade. In fact, if you walk through the rainforest you will notice that the seedlings on the floor of the forest in the dense shade are not growing – they are sitting in a dormant state waiting for a gap to form in the canopy so that the sunlight can stream in. It is only when they receive full sunlight that they start growing.

If you plant your rainforest plants in the shade, they will grow slowly, and they will become thin and lanky as they struggle upwards to the light.

Rainforest plants can, and should, be planted in the full sun, where they will grow thick and bushy and flower young. In their natural habitat, most rainforest plants do not flower until their canopy is in the sun. By planting them in the full sun from the start, you will trick them into believing they are already at the top of the canopy.

Of course, this does not apply to the shade dwelling understorey shrubs of the rainforest – these naturally need the shade – so use your commonsense!

Myth : Rainforest plants are too large for ordinary gardens.

Wrong! Most rainforest plants grow in the garden to only about a quarter or a third of their height in the forest. By planting them in the full sun from the start, they have no need to grow taller and taller to reach the sunlight, since they think they are at the top of the canopy already. I wonder how many of you have an Ivory Curl (Buckinghamia celsissima) or Golden Penda (Xanthostemon chrysanthus) in your gardens? Would you have planted them if you had known that they are rainforest trees from north Queensland, where they commonly grow 20-30 metres tall in the forest? In cultivation, however, they are rounded shrubs of only about 5-8 metres, and this is true of most rainforest plants, with the exception of plants such as the Kauri Pine and Bunya Pine.

Myth : Rainforest plants should be planted under a canopy of existing trees.

Wrong! Plants planted close to existing trees generally do poorly due to root competition and lack of sunlight. Take the plunge, and plant your rainforest trees in the sun from the start. Most of our rainforest plants for sale are in the full sun in the nursery, so don’t be afraid to plant them in the sun in your garden.

Myth : Rare plants are difficult to grow.

Wrong! Some rare plants are quite hard to grow, but many are surprisingly tough and hardy. Rarity is often more related to habitat isolation, than to any intrinsic feature of the plant itself.

Myth : Rainforest plants can only be grown in soil that matches the soil type in the wild.

Wrong! Rainforest plants can be grown in almost any type of soil. Mulch and loose soil are the main requirements; fertilise if necessary.

Planning your rainforest garden

To create an attractive rainforest garden that is pleasing to the eye, you need to use a fair proportion of hardy, bushy species that will give the garden its basic structure, bulk and backbone. There are many species that fit this bill, but some examples are the hardier, tougher Syzygiums and Acmenas, and plants like Flacourtia, Scolopia and Xanthostemon.
Pay special attention to the plants that you place on the edge – these are the ones that hit you in the eye every time you look at your garden. On the edge, you should place the plants that have an attractive shape, attractive foliage or spectacular flowers and the plants that could be smothered if placed in the middle of the garden.

Leggy plants are best in the middle.

Your garden should include where possible plants for birds and butterflies, flowers and fruits. The Yuruga Information Sheets ‘Attracting Birds’ and ‘Attracting Butterflies’ give you more information.

Having taken this approach, then you can start placing the more unusual plants that have specific requirements in and amongst this basic backbone.

Happy Gardening!