Propazine Has Little Effect on Growth of Several Containerized Woody Plant Species

Abstract

Woody plant species were treated in 1995 and 1996 with 0, 1, 2, or 4 lb/acre (0, 1.1, 2.3, or 4.5 kg·ha-1) propazine (a.i.). Species studied in 1995 included rose-of-sharon (Hibiscus syriacus L. `Double Purple'), japanese boxwood (Buxus microphylla Sieb. & Zucc. `Green Mountain'), butterfly bush (Buddleia davidii var. Veitchiana Rehd. `Nanho Purple'), euonymus (Euonymus fortunei var. acutis Hand-Mazz. `Emerald n'Gold'), forsythia (Forsythia ×intermedia Zab. `Lynnwood Gold'), fire thorn (Pyracantha angustifolia Roem. `Gnome'), and japanese spiraea (Spiraea japonica L.f. `Goldflame'). Crape myrtle (Lagerstroemia indica L. `Acoma' and `Zuni') and juniper (Juniperus chinensis L. `Pfitzeriana') were added and euonymus and japanese spiraea were omitted in 1996. In both years, statistical analyses revealed differences in height and visual quality between plants exposed to propazine and control plants of some species; however, differences were inconsistent in that some plants treated with propazine were larger or rated better than control plants while other plants were smaller or of lower quality than their corresponding control plants. In all cases, differences among propazine treatments within each species were <1.2 inches (3 cm) in height while decreases in visual quality compared to control plants were most evident in plants receiving four times the recommended rate of propazine. The horticultural significance of these differences was, therefore, considered small, suggesting that all of the species tested are tolerant to propazine applied at the recommended rate of 1 lb/acre (1.1 kg·ha-1). Chemical names used: 6-chloro-N,N'-bis(1-methylethyl)-1,3,5-triazine-2,4-diamine (propazine).