Winterkill is an ominous-sounding word – so injurious and final. Generally, the best approach is to be proactive, not reactive, when dealing with winterkill. Most other maladies are best dealt with in this manner as well, including insect infestations, planting and seeding operations, soil compaction, fungal infections and irrigation-equipment installations. Fixing problems after the fact is always tough, akin to putting toothpaste back in the tube.
Things worth worrying about
The main areas of concern when trying to prevent winterkill are desiccation of turf crowns and evergreen tree leaves and buds, as well as root dieback. These are major concerns due to the loss of tissues. Unlike turf and deciduous tree leaves, which arise in spring from perennial crowns and meristems, the crowns and buds of evergreens are considered permanent or semi-permanent structures. If they are lost due to winterkill, the usual result is total plant loss.
Root dieback is often just as destructive as crown and bud loss. To remain hydrated, turfgrasses and trees need to absorb moisture through their roots; if they are diminished through dehydration or cold temperatures, extensive damage is the usual result.
Nip problems in the bud
The first step in winterkill prevention is to identify problem areas, specifically turf cover and ornamental plants that have either historically been prone to damage, or have been reported to be a concern at nearby courses. Newly installed plant material often makes this identification process more challenging because it’s a change. New cultivars, species, location and similar factors should be considered “part of the picture,” as opposed to golfscapes that remain largely unchanged.
Damage prevention efforts should focus on high or exposed tees and greens. Drying winds in these areas can reduce available water within the crowns and roots to the point where they are unable to recover in spring. Similarly, low areas are likely to be damaged by a lack of oxygen caused by standing water or winter ice.
Windbreaks that separate fairways and screen undesirable views, and valuable conifer specimens on signature holes, are also subject to injury. Because they remain evergreen, losing small amounts of moisture throughout winter – and limited capacity to translocate moisture due to frozen soils – often dehydrates needles and buds to the point of being nonfunctional by the time favorable growing conditions return in spring.
Staying ahead of the threats
Fortunately, there are several options for damage prevention, the most obvious of which is maintaining adequate soil moisture before the onset of winter. If winterkill has been harsh in the past, watering to create a rooting zone that is on the slightly heavy side of moist – not too soggy, not too dry – is something to consider.
Another option is to install covers for greens and tees, especially those that:
- have been injured in the past,
- are newly established, and/or
- are elevated.
Supers have several options when it comes to the fabric and its density. In most situations, covers should be put on after the final mowing of the season and removed in the spring, once temperatures are warm enough to avoid injury. It is important that the placement of covers in the fall can’t happen until after the turfgrass has had time to go through some of the hardening off process for winter.
If supers put them on too soon, grasses may be injured when there is a rapid drop in outside temperature due to a poor balance of crown moisture and cold-hardiness. If the spring weather conditions are fluctuating, it may be necessary to remove and reinstall them, keeping daytime and nighttime temperatures in mind. It can be a time-consuming task, but if the return on investment is considerable, the practice is worthwhile.
If you are not sure whether to install permeable or impermeable growth covers, it might be wise to install permeable covers. They might not provide as much protection but they can be left on for months at a time.
After topgrowth has ceased in late fall, supers can apply a light balance of soluble nitrogen and potassium to expand the root system and enhance stress tolerance of winter conditions. Rates vary, but ranges of 0.2 pounds to 0.4 pounds of nitrogen per 1,000 square feet usually produces good results. After the fertilizer has been applied, rinsing the product off the grass and into the upper root zone with water is recommended.
When topdressing to protect turf from winter desiccation, apply enough sand to bury all of the turf except for the tips of the leaves. In most cases, the grasses should still be green but not actively growing.
Also, it is important to take care when selecting topdressing materials. The topdressing on greens should be as closely matched to the underlying rootzone mix as possible to minimize potential “capping” of the green.
If the rootzone is relatively unknown, a particle-size analysis should be performed to ensure infiltration-rate integrity can be maintained. If you have any questions about this test, contact your nearest turfgrass extension professional.
Another potential benefit to heavier, late-fall topdressing applications is that some sand may already be in place for spring aerification.
Damage to turf and ornamentals near parking lots often shows up in spring due to excessive applications of ice-melting products. In most cases, it’s necessary to apply these materials to limit slipping and injury to members and guests; the last thing that the green committee wants is a liability claim because an attendee of the annual Christmas gala slipped and broke a hip on the ice when it could have been prevented.
Like fertilizer for turf, ice-melting products for the parking lot and sidewalks have different characteristics.
The most effective product in terms of melting capacity is sodium chloride. Unfortunately, it’s also the most caustic option to plant material. Calcium chloride is less damaging, but also less effective at removing the buildup of frozen solids.
It’s pricey, but calcium magnesium acetate produces good results when melting ice and risks only limited burn to turf and trees.
Using a mixture of sand and ice-melt products is another approach to give visitors sufficient traction to avoid slipping while minimizing the amount of chemicals needed to do the job.
Applying anti-desiccant to protect valuable evergreen trees, shrubs, vines and groundcovers can be very helpful over the winter when it comes to winterkill prevention.
Considered by most horticulturists and arborists to be a “light horticultural wax,” these products coat the leaves with a material that helps retain moisture for as long as seven weeks. Generally speaking, an application schedule of Thanksgiving, Christmas and Valentine’s Day would be a good starting point in most situations.
How to recover when damage is done
It’s unrealistic to expect that all valuable turf and ornamentals will come through the winter unharmed by Mother Nature. Therefore, as important as prevention is, it’s probably inevitable that you will be correcting damage in the spring. With turf, regrassing is the main activity.
Depending on the severity of the damage, supers can turn to sodding, plugging, sprigging or overseeding. They can overseed during spring aerification to take advantage of the soil cultivation process that’s already in motion.
If more aggressive overseeding is required, supers can consider a multiple-layer approach, which involves applying grass seed at multiple levels within the turfgrass system.
For example, prior to aerification or verticutting, supers can apply a layer of grass seed. Then, after cultivation, they should apply another layer of grass seed.
When verticutting or aerifying in multiple directions, supers should apply seed prior to each event. They complete the process by dragging and topdressing, and when finished, the grass seed will have been placed at multiple layers within the turfgrass/soil interface.
When trees, shrubs and perennials suffer winter damage, the first step is to make a quick evaluation to determine if the plant can be repaired, or if it needs to be replaced. If less than 30 percent of a pine, spruce, holly, rhododendron or euonymous mass is browned out, removing the tissue through pruning will enable new growth to fill in the voids and keep the plant as an asset in the golfscape.
If more than 30 percent of the leaves and stems are injured, the best course is usually replacement. Of course, this is both a cost and an opportunity.
The cost is the disappointment of members, the price of the replacement material, and the labor needed to dig out and plant new stock. The opportunity is a chance to install plant material that is hardier and has the disease resistance and aesthetic appeal needed for years to come.
As winter approaches, supers should start taking a closer look at the areas that are potentially at risk for winterkill. Look for areas with poor drainage, areas that historically have little or no snow cover and areas that have heavy thatch buildup. Place an as-built map of your location on a break room table or in a common area and encourage the crew to mark where they have seen or experienced any potentially problem areas. It might give you an additional tool to prepare for a successful season ahead.