Author: Andy Cotter
The summer of 2022 brought unusually high temperatures and one of the worst droughts the UK has seen for decades. These conditions have left some trees already shedding their leaves in August to conserve water - despite summer not officially ending until 23 September. In some cases, the stress on a tree can result in significant damage to its structure, or even the death of the tree.
Councils will need to be aware that as well as the usual tree maintenance necessary in the autumn, they may need to consider additional risks to the health and structure of trees in public spaces. This is not just due to the drought conditions, but also from flash flooding which can cause further damage and instability to trees and their roots.
The impact of drought
During prolonged drought conditions, roots are unable to gather enough water to sustain them and in severe cases, problems go beyond the loss of leaves and buds, and may cause die-back of branches for some types of trees. Heavily stressed trees can enter dormancy earlier than usual (a false autumn), meaning a shorter growing season for the tree.
Drought can also affect trees indirectly, by increasing their susceptibility to disease, insect pests and wildfire.
Soil saturation and flooding
The uprooting or partial uprooting of a tree is more likely to happen when the ground is waterlogged. We have already seen flash flooding across parts of England following the drought conditions, and it is likely we will experience more.
These extreme conditions can be potentially fatal for a tree because when soil becomes waterlogged its ability to sustain trees and plants declines due to roots being starved of oxygen. This can then lead to a build-up of harmful gases resulting in the death of larger roots which may go on to affect the tree’s stability over time. Exacerbating the issue, there can also be a deterioration of the soil structure around the tree, affected its ability to grip the roots and further increasing the danger of the tree falling.
Saturation is a greater risk in the summer than in the winter months (when roots are dormant), however, as damage may not show up for some time, it is an issue that councils should take note of when there have been significant flood events.
Potential issues of a ‘second spring’
When high rainfall follows a false autumn, trees can be tricked out of dormancy and experience extra spurts of growth due to a ‘second spring’ (also known as a false spring).
While this may not pose an immediate risk to the tree’s structure, any new foliage or blooms that appear may not withstand the cold temperatures of the winter, and the tree may be more susceptible to disease. It is worth noting that a tree should not be pruned during this time, or watered within two days of a predicted frost. It may be beneficial to employ the services of an arborist for professional advice.
If a second spring brings substantial rainfall, it may lead to soil saturation which—as mentioned above—is not typically a problem associated with autumn or winter.
Storms and high winds
If trees and their roots have been weakened by drought conditions, this may increase the risk of them being uprooted or having large branches ripped off during high winds.
Less obvious damage may also occur, which can lead to issues way after the storm event. For example, limbs and branches can be fractured and weakened, yet remain intact, trees can be partially uprooted but not fall, and broken branches can be lodged within the tree’s crown and fall down days, weeks or even months later. Tree inspections should be carried out immediately after a storm event.
Tree safety checklist
Below are some tips for councils to help maintain the health and structure of trees through the autumn and winter months, whether we are experiencing a false autumn or the usual seasonal changes.
- Remove diseased, decaying and dead wood immediately—autumn is a great time to do this as many trees will lose their leaves which can expose these issues.
- Clear fallen leaves away from landscaped areas around the trees so they do not stop the soil from allowing in water.
- Carry out grounds maintenance weekly in public spaces such as play areas and ensure the safe disposal of fallen branches, plants and foliage where necessary.
- Where the branches connect to the tree’s trunk ensure they are looking strong with no signs of damage or weakness.
- Ensure trees are not presenting a risk to the public or structures due to their proximity to buildings, overhead cables, etc.
- Young trees should be supported with staking, covers and/or mesh.
- Hazardous trees (classified as trees near the public highway, playgrounds and any other open spaces where people may gather or walk) should be inspected following periods of adverse weather conditions.
- If heavy snow is weighing down branches or limbs, wait until the snow has melted and the branches are less brittle to assess any damage.
- Ensure that contractors, such as tree surgeons, have Professional Indemnity (PI) insurance in place, otherwise any claim may have to be dealt with by the council’s insurance.
Gallagher specialises in insurance and risk management for the public sector and supports local councils and parishes across the UK. If you would like to speak to our team about any of the risks you may be facing as you work to protect and maintain your community’s open spaces, please get in touch.
*https://www.bbc.co.uk/news/science-environment-62582186
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