- General

How to Choose Healthy Trees

Cities without trees would be awful. They would be hot, shadeless, soulless and very boring. I love trees, they provide colour, interest, a sense of belonging, a sense of scale and are overall just great! Trees are often planted for the next or even next generation as many of them can take decades to mature. Choosing a healthy tree is really important because it could live for 100s of years. If you plant a damaged specimen, down the track, it is going to cost you money, cause you grief and put the development of a garden canopy back years.

A healthy tree is one that has no major wounds, has shiny green leaves, has no unusual growths, is sturdy, has good branch attachments in the U shape, has no pests attacking it, is not oozing any liquids or sugars and generally is looking good. When you look up into the canopy, it should block out most of the sky. If you can see large amounts of blue, then it could be a sign its stressed. Stresses could be due to possums and other wild life eating the leaves, lack of water due to drought, too much water due to floods or caterpillars and insects eating the leaves. There are also lots of diseases that could be attacking it or the tree is senescence – nearing the end of its natural life. Also make sure you don’t confuse autumn leaf drop with thinning canopy of a sick tree.

When buying a new tree from a nursery, you have the right to pull the tree out of the display and walk around it, checking it out for any broken branches, wounds or any other defects. If you find any do not buy that particular specimen. Also look at how long the the plant has been in the pot. If the roots are popping out the bottom, the potting mix looks dull and lifeless and there are weeds growing in it, it is highly likely that this plant has been in the nursery for more than 12 months and is probably root-bound. This is not a good specimen to buy.

Root bound trees are where the roots have grown round and round and round themselves in the pot and will continue this way when they are planted out. This is a problem because as they mature there is no root system anchoring them to the ground. A gust of wind can knock it over and cause a lot of damage to you and any building it falls on. To prevent this is it always important to tease out the roots of any trees grown in pots before you plant them.

Understanding a Trees Root System

There are two types of roots – structural and feeder. The structural roots are the ones that anchor the tree to the soil and can be a thick as your forearm or thigh. The feeder roots are delicate, absorb the water and nutrients, are white, only live for a day or two and are constantly being replaced. They are located at the end of the root system. They are very easily damaged. Roots general grow laterally and sometimes you can follow a structural root for many many meters. You often see this when walking in the bush and it is fun to try and see where it is going. It is really really important you don’t prune off any structural roots because you may inadvertently create an unstable tree.

How to tell if a sapling is anchored firmly in the ground.

The Burnley method devised at Burnley College Melbourne, is a simple test to see if the sapling (young tree) has established a good root system. This is a test for a tree that has been in the ground for several years. Stand in front of the tree, place both your hands on the trunk in front of you and see you can rock the trunk. If you can feel it moving in the ground and/or see the ground heaving at the base of the trunk, then this tree could have something seriously wrong with its root system. This could be due to disease, damage or insects attacking the roots. If you do nothing and leave the specimen as is, it will develop into a potential risk.

There are two options, remove it immediately or stake it during the growing season and see if this will help it firm up. Remember, you must remove the stakes at the end of autumn. If it is still moving in the ground, then the hard decision of removing the tree may have too be made. Long-term staking actually hinders trees establishing a secure root system because the trees become reliant on the stakes to hold them up and it prevents them from moving in the wind and being forced to establish a strong root system. Never, leave a tree staked for years and then remove it. The next windy day, will blow your tree over or worst snap it off at the base.

The reason why the tree hasn’t established a strong root system is mostly due to being root bound and that is why it is important not to buy trees that have been in a nursery for years. They are not safe trees. Also when buying a tree from a nursery, look at the ratio of canopy to pot size. This will determine whether the root system is big enough to support the tree when planted. I have seen some trees with huge canopies and very tiny root systems. There is no way that the root system can support the weight of the canopy. Don’t buy these top heavy trees, they are an accident waiting to happen.

How to Plant a Tree Properly

Planting a new tree properly is really important because you want it to develop into a strong and healthy specimen. Firstly, it is important to dig a wide hole rather than a deep hole, (as long as it is a deep as the pot the plant came in) and that is because there a myth that plant roots grow vertically. In reality most plant roots grow laterally (sideways) as this is where most of the oxygen is. The deeper down, the less Co2 is present and therefore the roots can not respire (taking in oxygen). The majority of the trees roots are in the first 1/2 meter of soil where most of the oxygen and moisture is. Many trees die because they are incorrectly planted; they are planted either too deep or too shallow.

If the trunk is too deep, the roots can’t get oxygen and the trunk will rot. If the roots are sticking out above the soil, then they will dry out and eventually die. The correct way to plant is to have the join where the trunk and roots meet planted at ground level. And if you are not happy with the first planting, pull it out and try again. (Warning, do it immediately, do not let several months go by because you could like the tree). As the tree matures, you should be able to see a nice flair at the base of the trunk developing. If you can not, then it is incorrectly planted.

Tip: To help prevent root balling – dig a square hole – it forces the roots to grow laterally.

I don’t believe in putting at the bottom of the hole compost, animal or fertiliser because when it decomposes, it causes the tree to sink, thus causing it to be planted to deeply. Compost and animal manure also can hold onto the water, making it unable to the new plant. This causes the root ball to dry out as it is almost impossible to rewet it again and they die. I do believe in putting compost, manure and mulch around the plant when I have finished back filling with the unadulterated soil that I have dug out of the hole. For any tree issues I recommend you employ a qualified arborist who has the expertise to understand what is happening within the tree’s biology and root system. It may be expensive but it is money well spent. If you are unhappy with advice, then I recommend getting a second opinion. Enjoy your trees.