Archives for December 2018

In ‘The Best Trees for Cairns’ Crazy Weather Part 1’, we discussed the Cairns weather and its effect on trees and looked at the factors that make a tree wind resistant. In this article, we’ll look at the factors that cause trees to be considered unstable and identify the trees that you probably don’t want in your yard.

The factors that constitute trees that are unstable and unsuitable in storms include:

Damaged, sick, old or dehydrated trees – this is pretty self-explanatory. Sick or old trees will be weaker and things like termites (which commonly affect Eucalypts in Cairns) and dehydration can cause trees to break off at the trunk during storms.

Top heavy trees – trees with thick or heavy foliage and crowns generally give too much wind resistance. An example of a top heavy tree would be Fishtail Palms and the exception to this would be heavily foliaged trees with deep taproots, such as Mango

Poor root systems – large, strong taproots are key to ensuring a tree remains in the ground. Trees with shallow root systems frequently topple during cyclones, but it’s not just the species that determines the integrity of the root system – the quality of soil and frequency of watering during development plays a huge part. Trees should be planted out before they are 1 year old and those that are root bound should be planted well away from habitation.

Soil quality and density – If the soil is very sandy or very clay-heavy (which affects developing roots from being able to penetrate the ground properly), the root system will not be strong. Erosion from natural causes or development will also affect the strength of root systems.

No wind stress during development – If a tree does not experience enough exposure to wind during its younger years, its root system will not develop sufficiently. Lack of wind stress can be caused by a tree growing behind a wind break, a tree being staked for too long, a tree that is over 1 metre tall when planted and other similar situations.

Trees planted in rows – Unlike trees planted in clusters (mentioned above), trees planted in rows as a windbreak (i.e., with the row running against the wind, rather than with it) have no protection from in front or behind, so they generally fall.

Badly pruned trees – trees that have not been properly pruned or lopped develop weak points or become unbalanced, leading to a greater chance of falling or dropping branches.

The absolute worst trees to have during a cyclone include, but are not limited to: Caryota urens

(Solitary Fishtail Palm), Citharexylum quadrangulare (Fiddlewood), Corymbia citrifolia (Lemon-scented gum), Corymbia torelliana (Cadaghi), Eucalyptus camaldulensis (River Red Gum), Eucalyptus tereticornis (Forest Red Gum), Grevillea robusta (Southern Silky Oak), Khaya senegalensis (African Mahogany), Peltophorum pterocarpum (Golden/Yellow Flame), Spathodea campanulata (African Tulip Tree), Tabebuia aurea (Golden Trumpet Tree).

The best guidelines for planting in cyclone prone areas like Cairns is simply to not plant large trees near homes or other buildings; however, this is not always practical and you may have existing large trees that you can’t remove. So, your second best bet is to have your trees checked regularly by a professional arborist to ensure they’re healthy and not likely to fall. If your tree is identified as a species likely to fall, an arborist can advise you on what to do to prevent it. Cairns Tree Services can help you with all of this and more, so give us a call and we’ll keep you safe during the next cyclone season.

If you’re a Cairns resident, you’ll know how absolutely crazy our weather can get. One minute the sun’s sparkling off the sea, then 5 minutes later, the sky has turned green, the wind has whipped up and there’s a code black weather warning! Thankfully, most buildings and other structures are cyclone safe and locals generally know what to do in a weather emergency; however, there’s one aspect of weather safety planning that’s often overlooked – the safety of surrounding trees.

The safest thing you can do is ensure there are NO tall trees within falling distance of a building, infrastructure or other places where humans congregate. This is because there’s no such thing as a tree that can withstand all types of severe weather. The problem with that tip though is that trees are great and we usually want them around. They assist the environment, look beautiful, can add value to your property and as you’ll see below, they can even help protect your property during a storm, so how can we find that balance between enjoying trees in our yards and staying safe during the storm season? You can ensure dangerous trees aren’t present and plant wind resistant ones instead!

The factors that influence wind resistance include the tree’s root system, the tree’s foliage distribution and density, as well as changing factors, such as the wind intensity and the wetness of the soil at the time of the storm. While wind intensity is the one factor that cannot be deliberately changed, the type of tree (cyclone friendly roots and foliage) and where you plant it (soil with good drainage) can be. We look at other factors, below.

The characteristics that constitute a wind-resistant tree include:

Good flexibility – trees with thin, flexible branches, such as some palms.

A deep or well-developed root system – trees with large taproots are the best, but good root systems can be weakened by factors such as trees planted around concrete or those who have had roots cut by road works or similar

Fast defoliation rate – this refers to a tree’s ability to drop leaves easily during winds etc.

Foliage thickness – fine/thin leaves on plants – such as those on She-oaks, Leptospermum, Poinciana, Bottlebrushes and similar – offer less resistance than those with broader leaves.

Density of branches or canopy  – trees with open branch systems, such as Milky Pines or Sea Almond, let the wind pass through easily, reducing resistance.

Size and weight of crown or canopy – trees that are top heavy are obviously more prone to falling

Tree health – healthy trees with no damage, pests or disease and those that grow slowly are tougher and less likely to fall.

Trees planted in clusters – trees planted in clusters can still come down, but the windward side trees usually fall into the trees behind them and the other trees are sheltered from the wind, protecting the cluster from falling completely.

Some species of wind resistant trees include, but are not limited to: Alstonia actinopyhlla (Milky Pine), Arenga australasica (Native Sugar/Honey Palm, Calophyllum inophyllum (Mastwood, Alexandrian Laurel), Cryptocarya hypospodia (Laurel), Cycas spp. (Cycads), Euroschinus falcatus (Ribbon Wood), Ficus rubiginosa (Rusty Fig, Rock Fig), Mangifera indica (Mango).

In ‘The Best Trees for Cairns’ Crazy Weather Part 2’, we’ll look at the factors that cause trees to become unstable in storms, as well as identify the species that you shouldn’t plant in Cairns. If you’d like your trees identified or checked for their wind resistance, give Cairns Tree Services a call and we’ll get back to you ASAP.