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COOLmob met up with Darwin local David Liddle, former NT Government ecologist, to chat all things trees and shading in the backyard. Did you know that shading from trees can help you live comfortably, cool and air-con free – even in Darwin? We went out to his home in Brinkin to check out his garden, and what a green oasis. 

In Darwin’s tropical climate, being able to reap the benefits of shade from trees means you are able to cool your home for free, whilst also contributing to a bigger- picture urban forest. Urban forests are made up of all the trees and vegetation in a suburb, including streets, private property and parks and provide communities with physiological, sociological, economic and aesthetic benefits. Urban forests reduce what is known as the urban heat island effect, where temperatures stay warmer longer due to the many heat absorbent surfaces in cities such as roads, footpaths and buildings.

Effective shading can block up to 90% of this heat from direct sunlight, so by shading a building and its outdoor spaces you can reduce temperatures, improve comfort and save energy. Also, we’re home to some amazing birds, reptiles and other animals in Darwin, and trees play a huge roll in providing a habitat for these species to thrive!

So if you’re a backyard beginner or looking to plant trees more strategically, we have all the info to get you on your way to a very well shaded home!

COOLmob: So David, can you tell us a little about yourself?

David: My family moved to coastal Brinkin 6 years ago moved from Leanyer, and I’ve always had the joy of playing with a garden. I have had a long involvement with the Top End Native Plant Society and over 3 decades of experience with trees and plants!

COOLmob: Well it definitely looks like we’ve come to chat to the right guy! For our beginner gardeners out there, what are some of the first things we should consider when planting trees at home? 

David: The first step is to think about what you want to achieve. It’s important to think about the big picture, is it shade, habitat for wildlife, screening from neighbours or what is your main priority?

Also, remember to think about the future, are you looking for a tree that will reach maturity in 5, 10, 20, 30 years? Many plants and trees have the capacity to keep on growing. I am keen on growing a mix, both fast and slow growing trees, and I also like to enjoy plants for a few years and then remove them so longer term trees can take their place. 

You should also consider your soil and landscape. Where we lived in Leanyer, we were at bottom of slope and it took us a few years to realise that we were tapping into ground water. Because of our downhill position, our trees were accessing water from all the people upslope watering their plants. We had a really lush, green and shady garden that we didn’t really ever water (to keep he trees going). We were lucky that our trees were able to get their roots into ground water.

Which leads to my next tip, your ability to water is very important, particularly for the first few years. Typically, (mature) gardens in Darwin suburbia will have access to water scattered (about to water other plants), and most trees don’t need to be watered too much once they’re established.

COOLmob: Love that tip about thinking big picture and in a timeline! What about when choosing the positioning of trees?

David: Well, in terms of shading, the eastern and western ends of house are the best places to shade as this is where the sun hits the house when it is low in the sky, early in the morning and late in day. This is a strategic use of shading trees and very, very beneficial for heat mitigation.

When we lived in Leanyer, we didn’t have air-conditioning, but our house was super shady. But, when we were selling that house, everyone was shocked we didn’t have air-conditioning and used that as a bargaining chip (which we expected)! But the funny this was, a year or so later, we met the people who bought the place in the supermarket, and they said “wow the house is really cool, we haven’t had to put in air-conditioning!”

A contributing factor of this was the shading trees on west and east end of house, but what we’d also done was, on northern side, we’d deliberately planted trees well back from the house, close to the front fence. This gave us lots of screening at the street front for privacy, but also enabled for a great breezeway and airflow. This combination was a balancing act, positing for shade also as well as air flow.

Other aspects to consider when choosing where to plant include what infrastructure is around, like it doesn’t make sense to plant on sewage easements, water mains or near telecommunication lines.

And maybe most importantly, remember to consider your neighbours! Often people plant really big trees right on their boundary, without having a conversation with their neighbours, but you need to think about how you see them using their yard.

David's balcony is very well shaded but also has great access to breezes, which was considered when planting. The greenery from all the trees transforms the balcony into a green oasis.

COOLmob: Ah yes, we want to promote neighbourliness! How much maintenance would you say involved in having lots of trees in your yard?

David: In my experience very little, but that’s not always, as it comes down to having the right tree in the right condition. I think it is delusional to think there won’t be any maintenance, but you can minimise maintenance. If you plant a deciduous tree near a pool, you will be cleaning the pool when the tree sheds its leaves. If you grow a fruit tree that drops fruit you don’t eat, then you’ll be cleaning that up.

To minimise maintenance:

  • Consider the tree’s size when planting
  • Dig a big hole so roots can anchor and become established
  • Water a bit each day when first planted, then quickly move to every few days, then weekly etc
  • Keep leaf litter to put back into your garden to recycle the nutrients. I’m really keen on keeping organic matter in the yard, like letting palm fronds decompose.

COOLmob: Now onto cyclones – what can we do to minimise cyclone damage?

David: Here, I come back to planning. One of the good things to come from Cyclone Marcus, was that City of Darwin Council put a lot of effort into how trees performed in the cyclone, including looking at wind firmness. There is a great resource on Council’s website with a list of a couple of hundred of preferred trees, and majority are NT natives, with a great bias towards a high element of wind firmness.

The other good source of knowledge it look around your local area – if you don’t know what’s there, I encourage you to talk to people. You can get a good idea of what works in your area, because if trees are still standing, they survived the last cyclone!

COOLmob: And what are some good dual purpose trees? Say I want shading, but I also want an edible garden.

David: The Kakadu plum is a great plant – it’s deciduous meaning it provides shade for half the year, it forms a lovely, shapely tree with an upright stem and spreading crown, meaning a big canopy of big leaves! Plus its fruit is very high in vitamin C fruit. 

Also, one of my favourite trees is the Syzygium forte, these are one of the bush apple trees. These trees have a great reputation for termite resilience and as well as providing edible fruit, being hardy, and growing into a big tree eventually!

COOLmob: Wow! Need you say more? These trees tick lots of boxes! Now jumping in here with a topic change, how big will things actually grow?

David: Plan plan, plan!! Trees are incredibly variable, they can be big, little or medium. The good thing to remember is that lots of trees in suburbia won’t get that big, even though individuals of them can grow to be massive. The Maranthes corymbosa tree is a fantastic shade tree, plus it’s tough, I love them as they tick lots of boxes and are wind firm. Out bush this can grow to 1m wide at the base and to 30m tall, so obviously this is too big for domestic gardens but I’ve never seen them this size in Darwin – meaning that in optimal conditions these trees can grow massive but in reality in Darwin these trees will unlikely become so massive.

COOLmob: And what can you recommend as a shade tree that also provides privacy screening?

David: Definitely the Carallia brachiata – one of my favourites! The Carallia brachiata is the same family as mangroves, but this isn’t a mangrove, it grows on terra firma! These are evergreen, with dark green glossy leaves, and lateral braches, meaning it’ll come up and spread out. Its branches provide excellent screening. Another is a Micromelum minutum, this is a shrub/small tree that can get to about 5 meters. After a few years these will start suckering, meaning multiple stems will come up with greenery for screening. In Leanyer, we had one right at the front fence, it came up and arched over the driveway, shading the drive and giving us fantastic screening! Also, what I love about these is that it’s one of the best butterfly attracting plants!

COOLmob: What’s the best time of year to plant in Darwin?

David: Early – mid wet season. Once the monsoon has really arrived I don’t like digging the soil because you can disrupt the soil constitution, and in Darwin you have to be careful for melioidosis. If you’re in the dirt in the wet season, you should wear gloves and shoes. The dry also works to plant but only if you are in a position where you can supplement your water.

COOLmob: Now for renters – I’ve moved house – I want to move the tree. What do I need to consider?

David: I haven’t done a lot of moving trees and certainly most people can’t move big trees, but in terms of smaller plants, it’s variable. Things like grevilleas, I wouldn’t bother with as the chance of survival once established is really low. Whereas rainforest plants have a bit of scope to move.

If you have a sense you’ll move, consider putting some things into pots. You can grow things in big pots and move them in 5 years. Chuck them in the back of a Ute and off you go!

COOLmob: What’s an ideal tree to plant in a big pot?

David: One I really like is Ficus benjamina – Not typically recommended for Darwin backyards because it can get very big with aggressive roots, but in a pot, for a miniature garden, it’s great because you can prune it and it will re-sprout. It’s got small leaves, but watch out for the roots which can easily sneak out of the bottom of a pot! You could put your pot on bricks to prevent this plant from ‘moving in’!

I think there’s a lot of plants around Darwin that will grow well in a pot. I grew an NT native Polyaulax (now called Meiogyne cylindrocarpa) in a pot for a couple of years, which we’d bring inside to use as a Christmas tree!

COOLmob: So there’s lots of renters in Darwin – any other tips for keeping their homes green?

David: I really recommend talking to your landlord. If you go in and plant something that will turn into a big tree, then sure, you’ll have maybe 5 years of joy, but you’re potentially making an issue for someone else down the track. Generally, if planting greenery is good for you due to shading or privacy, it’s good for their property – and they may even help fund the planting!