Page 12 - GreenMaster Winter 2023

PREPARATION IS KEY
When the decision has been made to control the tree roots on your property, preparation is crucial.
A clear idea of where you want to prune should be developed and marked out on a plan of the golf course. Keep in mind there may be areas that are difficult to access for the tractor mounted units. They can struggle on slopes and may not be able to get between objects such as greens and bunkers, or in some cases the tree itself may be too close to the green or bunker to get a tractor through.
The International Society of Arboriculture (ISA) has recommended guidelines for how close to a tree you should root prune to avoid negatively impacting the health, structure, and safety of trees. Less then 6 times Diameter at Breast Height (DBH) or 1.4 meters from the ground has been shown to cause sustained water stress symptoms in some tree species.
For an example, a tree with a diameter of 450mm, or 18”, you should try and stay at least 2.7m, or 9’, from the trunk. As with anything else that causes one form of stress to a tree, this can lead to other problems, so this proximity to the trunk should be monitored closely. Anything closer than this can create stress, as well as compromise stability and long-term health. If it is required to root prune inside this dimension, the tree should be closely monitored for structural stability.
An accepted guideline is to use the drip line of the tree as a limit to avoid excess stress to the trees. It helps to keep in mind that a tree with a drip line radius of 5m that has had unimpeded root growth could easily have a root mass that extends to a radius of 15m. If you were to root prune in a straight line at a point 5m from the trunk, you may effectively remove 30% of the tree’s root mass.
Once a plan has been made for where to root prune, lines should be marked on the ground for the operator to follow. This will also help if there may be irrigation pipe, or any forms of communication wire or third-party shallow utilities underground. These should be located and identified with a different colour of spray paint. Failing to protect underground utilities can easily cause damage worth much more than the cost of root pruning on an 18-hole course.
Stem girdling roots.
Lastly, the owner of the trees should be contacted for permission to perform root pruning. If the golf course is on leased land, the trees may be owned by the landowner. Municipalities can have bylaws in place requiring an ISA Certified Arborist be involved to protect the long-term health of the trees.
EXECUTING ON THE PLAN
So, the day comes to perform the procedure. Permissions have been granted, utilities and irrigation have been located, and the pro shop has done a thorough job of informing the golfers of what to expect. (Insert laughter here). If the preparation has been completed thoroughly, the process itself is relatively quick and painless. At 0.5km/hr, ideally you can get roughly one par 4 an hour done if you need to do the entire perimeter. It would be expected for the process to take 3-6 days to do an entire 18- hole golf course.
It is a good idea to ensure that you also flag surface infrastructure ahead of time. Make sure all irrigation heads, valve boxes, quick couplers, yardage markers, etc. are clearly identified. It is a common practice for this process to be done by outside contractors, so they will likely not be aware of what is in their way. It is also a good idea to isolate the irrigation located in the work areas as they go.
POST-CARE BEST PRACTICES
As with any cultural practice, the
followupcareiscrucial.Asignificant application of water after the root pruning will help buffer the impact of the root pruning. You may see signs of stress no matter how much you
apply, and it varies widely across different species.
Monitoring of trees should be done after a week, and then monthly for the remainder of the growing season. Inspect trees for leaning, wilting of the leaves, and any disturbances along the line of pruning. It is a good idea to monitor the root growth in the subsequent years, as they typically grow at least 600mm a year in much of our growing climates. I have witnessed poplar roots grow more than 3m per year.
If the process is completed around greens, be prepared to see the potential for damage to the greens for a year or two as the severed roots produce new shoots to try and survive. These suckers can produce thousands of shoots on a single putting green for months and years after being pruned. The removal and repair of damage from these can be very time consuming and therefore costly.
Should you see roots become exposed in bunkers or other surfaces, a product with the active ingredient triclopyr, present as butoxyethyl ester, has been shown to control the problematic roots. This product has also been used on roots not severed with minimal damage to the parent tree. As with any pesticide, apply only as directed.
PRUNE WITH CONFIDENCE
While trees are an integral part of many golf courses, they can be problematic in many ways. Hopefully this article gives superintendents knowledge of another tool in their arsenal to continue to improve the golfers experience! GM
12 • CGSA • GreenMaster
PHOTO CREDIT: THOMAS DEHAAS, OSU