Control of unwanted plants in clubhouse landscaping, tee box plantings and other non-turf areas on the golf course is vital. Not only are weeds invaders and competitors with desirable ornamentals, they can be easy to spot by golfers as they admire the perennials and groundcovers in beds.
Like weed control in areas of the course covered by turf, common-sense techniques including scouting and implementation of appropriate cultural practices go a long way toward control. Though many weeds can look similar at first glance, taking a little time to look closely and determine the exact genus and species is worth it.
Identifying a weed these days is easier than years ago when resources were scant. Now there are books with color pictures and descriptions, online tools from land-grant universities and pesticide manufacturers, and identification apps for smartphones.
1. Identify the common weeds in beds
Many of the same species that are found in fine turfgrass are also discovered in ornamental beds. However, in some cases, a wider range of weeds can be found in beds. Also, ornamental beds tend to be a favorable location for weeds to grow well.
Grassy weeds such as crabgrass, yellow foxtail, goosegrass, yellow nutsedge and tumble windmillgrass pose a threat to the aesthetic and functional quality of ornamental beds. In addition, desirable turfgrasses such as bentgrass, St. Augustinegrass, centipedegrass, zoysiagrass, Kentucky bluegrass and bermudagrass commonly invade beds and become weeds themselves.
Broadleaves including spotted and prostrate spurge, field bindweed, ground ivy, prostrate knotweed, white clover, oxalis, speedwell, red sorrel, wild violets, dandelions, plantain, dollarweed, purslane and henbit are also commonly problematic.
Read more: Whack the weeds
2. Prevent defense
When it comes to weeds in ornamental beds, it’s usually easier to prevent them, rather than control them. Post-germination control measures such as herbicides can damage the desirable ornamentals, while hand pulling is usually quite laborious.
With any weed control effort, much of the difficulty stems from the sheer number of weed seeds in the soil. Weed scientists report that there are between 10,000 and 40,000 weed seeds in the average cubic foot of soil. When moisture and sunlight are present in sufficient quantity, they will germinate, grow and become pests in the golfscape.
Several preventive control strategies have been developed for beds. One of the most effective is applying mulch over the soil. Many types of organic and inorganic mulch are available, each with pros and cons.
Generally, the organic types including bark, pine needles, wood chips, corn cobs and cottonseed hulls, which offer good weed suppression, moisture retention, decomposition that improves soil health and create a natural, aesthetically pleasing appearance.
In terms of disadvantages, they tend to blow away over time and require reapplication. Occasionally, when condit-ions are dry for extended periods, mulch can develop into a water-shedding material, functioning similarly to a thatch roof. If this occurs, the problem can usually be remedied by light raking and watering.
Inorganic mulches include rock, stone and rubber particles. The positive aspects of these products are reduced blowing potential and need for replacement. On the negative side, the initial cost is usually greater than organic mulches and they tend to add much greater heat to the landscape, which stresses the ornamental plants. Unfortunately, they don’t decompose over time and add organic matter to the beds.
Weed barriers, both plastic and geotextiles, are often suggested as products to prevent weeds from becoming established in ornamental beds. Unfortunately, they often fall short of the desired outcome, as soil blows in over time and/or mulch decomposes, creating a good rooting medium for weed germination. In many cases, weeds begin growth and develop, often rooting in the actual prevention fabric itself. In other situations, the material tears, loosens or cracks, allowing weeds to germinate from the soil beneath.
Equally as effective as using well-suited mulches is the encouragement of healthy ornamental plants that become vigorous and outcompete weeds in the beds. Several steps are involved with this approach beginning with soil testing, and creating a soil medium that will support and promote healthy plants.
Once the infrastructure for ornamental beds are in place, the next step is to choose well-suited plants for the growing conditions of the site – sometimes referred to as “right plant, right place.” There are many considerations for this process, including sunlight, soil moisture preference, disease resistance, height/width, season of bloom, spring/summer/fall/winter color and growth habit.
Pre-emergent herbicides can be an effective tool in preventing weed competition in beds. Several products are available, each with their own limitations and capacities. Usually, the most effective approach is to determine which weeds have been problematic in the past and choosing pre-emergent products to prevent them. Pre-emergent products include pendimethalin, oryzalin, prodiamine, trifluralin, isoxaben and metolachlor.
Regardless, before applications are made, it’s crucial to read and follow all label directions. As well as product rates and water-volume guidelines, helpful information regarding water pH and calibration guidelines are often included on the label.
3. Use the curative approach
No matter how one puts it – pushing a big rock up a steep hill comes to mind – controlling weeds after they have germinated in an ornamental bed is much more difficult than beforehand.
There are basically two methods of curative control. The first is mechanical, involving digging, pulling and/or hoeing. This method may seem laborious and downright ridiculous if a large bed or many beds are involved. Yet, if the course has become the benefactor of temporary inexpensive labor via work programs, summer interns or community service participants, then it’s not such an outlandish idea after all.
The important initial consideration in this approach is to spend a little time training the workers on what is a weed and what is a desirable ornamental. Once the bed is cleared of weeds, then organic mulches can work well as a preventive step going forward.
The second method is to spray undesirable weeds as they emerge with herbicides that harm the weed without harming the perennials, groundcovers or the like. The big message with over-the-top herbicides for weed control in ornamental beds is using caution.
Yes, several options exist for both post-emergent broadleaf and grassy weed control. Yet, the key guiding principle is that killing plants that are not the desired ornamental species is different that doing so in a fairway, where the turf is a monoculture and the weed is an outsider. In a bed, there may be several different species of ornamental plants – bulbs, shrubs, trees, groundcovers, flowers, (some annual, some perennial) – and several different species of weeds. All of these factors call for well thought-out and well-researched plans of action.
Consulting extensively with manufacturer representatives, university extension faculty and other green industry professionals is a wise step to gain information about both weeds that are likely to be controlled as well as the likelihood of phytotoxicity to the ornamentals in the bed. Products to consider include fluazifop-butyl, clethodim, sethoxydim and imazaquin.