Rather than rebuild native soil or “push-up” putting greens entirely, expansions are often added to create opportunities for new hole locations. In some cases, the existing soil in the expansion area is suitable for maintaining high-quality putting green turf, but this is the exception rather than the rule. More often than not, some of the existing soil will need to be removed and replaced with a rootzone mix. For conditions in the expansion area to match untouched parts of the putting green, mix selection is critical.
Prior to selecting a rootzone mix, it is a sound decision to have a soil physical analysis performed on the mixes being considered and the sand layer from two or three of the existing putting greens. The data from this testing makes it possible to compare the rootzone mix options and the existing putting green soils to determine which rootzone material is the most similar to the sand layer on the greens that has developed from aeration and topdressing. Do not be surprised if the results show that a “dirtier mix” like a 6-2-2, 7-2-1 or 7-3 matches closely with the sand layer.
Consideration should also be given to how putting green expansions will drain. Having a water release curve performed on the mix that is selected will determine the depth of mix required for proper drainage. If drainage has been installed in the existing green and it is functioning properly, it should be extended into the expansions to provide an outlet for when the new rootzone material becomes saturated. If drainage has not been installed in the greens or is not functioning properly, a putting green expansion project is an opportune time to install drainage throughout the putting green. Some form of sand-channel drainage is typically the strategy used to improve internal drainage in push-up putting greens.
How turf is established on a putting green expansion will also have to be carefully planned. Putting green sod can be hard to find and variable in quality, so it is best to work with a sod farm well in advance to ensure sod that meets your standards will be available. Some superintendents choose to establish an on-site nursery to guarantee sod availability. This has the added benefit of allowing the superintendent to control the agronomic program for the sod that will be used, which can improve establishment and subsequent playability of the new expansion areas. If the putting greens have high populations of Poa annua, establishing an on-site nursery from aeration cores will be the best option for being able to install sod that matches the existing putting surfaces.
It is absolutely possible to expand greens and create consistent playing conditions across the entire surface, but it is important for testing to be completed during the planning process to ensure the proper rootzone mix is selected. It is also important to explain to golfers that it will take time for the newly established turf in expansion areas to mature. For assistance with planning your putting green expansion project, reach out to your regional USGA agronomist.
Central Region Agronomists:
Zach Nicoludis, regional director – znicoludis@usga.org
Paul Jacobs, agronomist – pjacobs@usga.org