Liner Dips for Growth Regulation of Vigorous Herbaceous Perennials

Many vigorous herbaceous perennials need early growth regulation. Treatment at the plug stage could improve early growth control or maintain product size in the plug tray. Concise (uniconazole, Fine Americas, Inc.), is a growth regulator labeled for use on ornamental greenhouse crops in the US. We treated plugs of five herbaceous perennials with a 2-minute dip into 0, 1, 2, 3, 4 or 5 mg/L Concise the day before planting into 1.1-liter pots filled with a peat-lite medium (ornamental grasses were maintained in the plug pots). Plant height was determined at 2 week intervals after treatment (WAT). Concise reduced shoot growth in a linear or quadratic correlation for all crops except Gaillardia x grandiflora 'Goblin' which was not affected by the treatments. The ornamental grasses differed in responsiveness with Miscanthus sinensis 'Gracillimus' showing little response until 8 WAT while Calamagrostis x acutifolia 'Karl Foerster' exhibited a 22% reduction in plant height at 2 WAT with a 1 mg/L Concise dip followed by a 31% height reduction and 26% reduction in shoot dry weight at 12 WAT. A 1 mg/L liner dip of Concise gave significant height reduction of Phlox paniculata 'David' and Rudbeckia fulgida var. sullivantii 'Goldsturm' through 8 and 10 WAT, respectively. Liner dips are an effective means of growth regulation that can reduce worker contact with the chemical solutions and provide baseline control of vigorous or hard-to-control herbaceous perennial crops.