Irrigation bag used to water Acer campestre ‘Elsrijk’.
As we're all aware, the summer of 2018 was very hot! For those involved with aftercare for newly planted trees, watering solutions were needed as part of the maintenance package to help them survive.
Sending a contractor to water trees can be expensive. In these financially constrained times, despite its importance, watering can be one of the first maintenance tasks to be scaled back. Understandably, with 4,400 miles of carriageway and footpaths, Worcestershire County Council Highways (WCCH) has to prioritise the many safety issues that are part of being responsible for the management of a vast amount of tree stock. As the term maintenance service contractor, Ringway Infrastructure Services is responsible for the delivery of all highways maintenance, including arboricultural services.
WCCH policy states that when trees are removed, where site conditions allow, replacement trees are planted. In order to facilitate aftercare, where possible, collaboration with district, town and parish councils enables combined watering of flowerbeds etc. with the newly planted trees. This is a very cost-effective solution. Nevertheless, this did leave a number of trees that were not being covered because of their location. Accordingly, we sought a cost-effective solution to undertake watering and decided to try irrigation bags. A small number were purchased to test their viability for watering in urban locations.
All the trees watered using this method were in city locations with tarmac surrounding the planting pit. The species irrigated consisted of 10 individual trees: Acer campestre 'Eisrijk', Tilia mongolica and Prunus 'Sunset Boulevard', mainly heavy standards of 12-14cm girth. After experimentation, the following method was found to be the most effective.
- A 25-litre plastic container was filled and taken to site.
- The irrigation bag was placed in position and filled from the container in situ.
- A large cable tie was used to attach the bag in an elevated position to allow gravity to aid water delivery and help prevent theft and the bag blowing away when empty.
- The hoses from the bag were positioned to provide the best water delivery, e.g. placed in the irrigation tube or directly at the base of the tree.
Issues to be taken into consideration
- Although the bags are of course designed to leak through the hoses, they can become holed and give less effective delivery where subterranean irrigation pipes are being targeted. In an urban situation where there are sharp stones etc. it is prudent to seat the bags on separate material such as sacking or a foam mat. Don't (as I did) fill the bag and then put it in the boot of your car only to find it has leaked. My boot had become a swimming pool!
- The nozzles on the ends of the hose are adjustable. I found, however, that removing the nozzles allowed an increased steady flow. This enabled the bags to empty more quickly and then be moved to the next tree.
- The capacity of the bags we used was impressive: they were capable of holding and dispensing 25 litres of water. This does make them somewhat heavy. Consequently, when adjusting their position, good manual handling technique is important to prevent injury. If you are of a smaller stature, you may consider it prudent to have two people on site.
Removing the nozzles allowed an increased steady flow.
- All trees that were watered using this method not only survived, they are thriving. Unfortunately, one field maple was missed out of the programme and this tree died in the first part of the heatwave.
- The method is extremely cost effective: the bags cost £18 per item and of course can be reused until they wear out.
- It takes a matter of minutes to fill them and position them.
- The bags empty in approximately 1-2 hours, depending on nozzle settings. Consequently, it is simple to set a drop-off and pick-up rota to move them between sites.
- It is a proactive tree management technique that generates considerable interest and approval from stakeholders. People seem to appreciate the method's simplicity and the fact that the trees are being looked after. Anecdotal evidence suggests that it incentivises members of the public to be more aware of their trees. Some began to use grey water to irrigate the trees themselves.
- The relatively small size and innocuous appearance of the items seem to have helped avoid malicious damage.
The trial was an unqualified success in keeping young trees alive. The programme will be extended if similar hot weather occurs in future summers and where other irrigation methods are not available.
Article taken form Issue 183 of The ARB Magazine. Members can view their copy here.