Weed Control Strategies for Field Grown Herbaceous Perennials

Abstract

Fourteen herbicides or herbicide combinations, wood chip mulch, chipped rubber tire mulch, and newspaper mulch were evaluated for weed control efficacy and phytotoxicity using 12 species of herbaceous perennials under field growing conditions. The effect of herbicide application time was monitored by applying herbicides to dormant and actively growing plants. Herbicide and mulch treatments were compared to weeded and non-weeded controls. Herbicide phytotoxicity was dependent on age and species of herbaceous perennial and time of herbicide application. Herbicide injury was generally greater for young plants compared to established plants and phytotoxicity was usually reduced when herbicides were applied to dormant rather than actively growing plants. Injury was sometimes greater when herbicides were applied in early spring compared to applications made after complete herbaceous perennial emergence. Injury to young shoots that had emerged prior to the earliest possible time that herbicides could be applied in the spring was probably involved. Applying herbicides in the fall may avoid such injury. Mulching field grown perennials with wood chips provided the most effective weed control and often the best quality plants. With the exceptions of Hemerocallis ‘After Dark’ and Phlox maculata ‘Omega’, the herbaceous perennials evaluated were tolerant of most of the herbicides applied. Several herbicides, including Balan 2.5G at 3.36 kg ai/ha (3.0 lb ai/A), Snapshot 80DF at 4.48 kg ai/ha (4.0 lb ai/A), and Stomp 60WDG at 4.48 kg ai/ha (4.0 lb ai/A), demonstrated potential for weed control in herbaceous perennial production systems and landscape plantings. Goal 1.6EC at 1.68 kg ai/ha (1.5 lb ai/A) and Ronstar 50WP at 3.92 kg ai/ha (3.5 lb ai/A) were often phytotoxic when applied to herbaceous perennials.

Herbicide-Treated Mulches for Weed Control in Nursery Container Crops

“…Derr (7) reported Surflan controlled spurge in container-grown herbaceous perennials, and in a separate study, in pots that were crop-free (13). Surflan, however, is often mixed with other chemicals to provide a broader spectrum of weed control (4,24,30). Surflan + pine nuggets was the best Surflan-treated mulch, and it provided some, but not complete control of spotted spurge in 2001, and it provided no control of the spurge in 2002.…”

“…Integration of two or more methods of weed control may produce a positive interaction (26). The combination of Surflan with another weed control factor such as another herbicide (4,24,30) or mulch (22) provides this positive interaction.…”

Impact of Mulches on Landscape Plants and the Environment — A Review

“…Organic mulches that are coarse, applied in thicker layers, and/or less nutrient-rich are more effective in controlling weeds -sometimes even better than herbicides (18,44). Locally-derived residues from crops (26,76,93,95) and forest products (19,26,37,46,57,95) have all proved effective in reducing weed success in a variety of agricultural and landscape situations, especially in uncomposted form (95). While some studies recommend the use of sawdust for weed control on forest lands (5,131) or in container production (90), others have noted that thick layers of sawdust can be impermeable to gas and water movement (120).…”

Effect of Different Types of Mulching on Soil Properties and Tree Growth of Magnolia champaca Planted at the Montane Rainforest in Cameron Highlands, Pahang, Malaysia

“…Mulching has been shown to improve survival in nursery and field production [9], Silvopasture systems [10], woodland plantations [11], and restoration sites [12]. Researchers discovered that mulched trees grew 67% faster than bare soil trees as early as 1942 [13]. Many others have since shown similar increases in tree, shrub, and other plant material development in field and nursery conditions [11,14,15].…”