Organic mulch is commonly used in landscape planting beds to improve plant growth and reduce competition from weed species. Although many different mulch materials have been evaluated in landscape, forestry, or agricultural settings, there have been no previous reports concerning the maintenance costs associated with different mulch materials from a weed control perspective. Trials were conducted at two locations in Florida to estimate the annual maintenance costs associated with pine bark nuggets (bark derived from pine species not specified) and pine straw mulch mix of longleaf pine (Pinus palustris) and slash pine (Pinus taeda) needles with and without the use of a granular preemergence herbicide when maintained at similar depths in schilling's holly (Ilex vomitoria 'Schilling's Dwarf') shrub beds and asiatic jasmine (Trachelospermum asiaticum ` Minima') groundcover beds. Weed coverage and residual mulch depth were tracked over time, with maximum and minimum thresholds (20 and 2 inches, respectively) set as triggers formaintenance activities. Results showed that the addition of herbicide (trifluralinD isoxaben) had little to no impact on weeding frequency or time when plots were mulched, but did reduce hand weeding frequency and time compared with nontreated, nonmulched plots. Both mulch materials used alone reduced hand weeding frequency and timecompared with herbicide- only treatments. Although results varied by bed type and location, pine bark generally provided greaterweed control compared with pine strawand required fewermulch additions and lessmulch by volume. Results from this study suggests that using pine bark nuggets as mulch may result in lower maintenance costs andweed pressure comparedwith pine strawwhen both are applied and maintained at 2-inch depths.
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