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New England Blade – Randy Prostak, UMass Extension Weed Specialist

As we build weed management programs for turf, it is important to take advantage of every opportunity at our disposal. One such opportunity occurs during the establishment and/or renovation process that often occurs in the turf areas we manage. It is at times hard to fight the temptation to adopt the “plant now and worry about it later” strategy. This is a path that will likely result in great regret down the road. Weed management at the start of a project can solve many difficult weed problems. The expression “let’s start with a clean slate” should be in the back of your mind as you plan and implement establishment and/or renovation projects in turf and landscape areas.

Situations where the “fresh state/clean slate” approach may be warranted

Turf:

1. Weeds cover exceeds 50 percent.
2. The presence of difficult-to-control weeds as a result of neglect and/or ineffective management.
3. Lack of effective cultural or selective herbicidal options for specific weed species.
4. Perennial weeds with asexually vegetative means of reproduction (creeping roots, rhizomes or nutlets).

Landscape:

1. The presence of difficult-to-control weeds (including invasive plants) as a result of neglect and/or ineffective management.
2. Lack of existing effective cultural or selective herbicidal options for specific weed species.
3. Perennial weeds with asexually vegetative means of reproduction (creeping roots, rhizomes or nutlets).

Implementation guidelines

A non-selective, translocated herbicide such a glyphosate is the most appropriate when implementing the “fresh state/clean slate” approach. Contact herbicides such as diquat (Reward), pelargonic acid (Scythe) and non-chemical products that contain clove oil, citric acid, acetic acid or orange extract are not suitable. These contact herbicides will not control perennial weeds, especially those with asexually vegetative means of reproduction.

Turf: In turf, the “fresh state/clean slate” strategy focuses primary around the establish of a new turf area when little, if any, of the previous turf is worth saving.

1. Late summer and early fall (August 14 to September 15) is the best time for turf establishment by seed.
2. In preparation for turf establishment, treat area with glyphosate, a non-selective, translocated herbicide in early to mid-July. If perennial weed regrowth is observed, another application can be made before seeding. There is no need to be concerned with summer annual weeds (crabgrass, carpetweed, spotted spurge and purslane) that may germinate this late is the season.
3. Collect and submit a soil test. Soil test results will indicate if corrective measures regarding soil pH and fertility are necessary.
4. Select a seed mixture appropriate for the site based on site conditions and intended turf area use. This mixture should contain turf species and cultivars of those species that are best adapted to the most limiting site factors (fertility, shade, moisture, traffic/wear and site use).
5. Seeding can be done with an overseeder and there is no need to remove the dead surface layer.
6. Turf establishment at the end of the growth season may not require a preemergence herbicide application. If annual bluegrass (Poa annua) is a problem, an application of mesotrione (sprayable or on-starter fertilizer formulation) will suppress this fall-germinating winter annual weed.
7. Application of a starter fertilizer (water-soluble, quick release) is recommended.
8. Irrigation should be applied in the absence of adequate rainfall.
9. In the spring following turf establishment, standard weed management practices should resume.

Landscape: In a landscape setting, the “fresh state/clean slate” strategy focuses primarily around the installation of a new landscape, as it may be difficult to convince your customer to rip out an existing landscape with the sole purpose of managing weeds. However, if the landscape ornamentals are overgrown and weeds, including invasive plants, are present, it might be something to consider.

1. Determine the most troublesome weed species at the site.
2. While glyphosate may provide acceptable control for many weed species, it might not be effective enough and another herbicide will need to be used or incorporated.
3. In most cases, the control of weeds should begin well in advance of the installation of landscapes ornamentals. For spring installations, weed management strategies might need to start the previous growing season. For late season installations, weed management can begin early in the season. While this may be viewed as a lengthy process, it is important to make sure that your weed management objectives are obtained before planting begins.

Reprinted with permission from UMass Hort Notes 2019 Vol. 30:1 February 1, 2019.