Agronomy and Horticulture Department


Date of this Version



HORTSCIENCE 26(2):209. 1991


Copyright 1991 American Society for Horticultural Science. Used by Permission.


This study was initiated to evaluate wildflower establishment using a preemergence herbicide. Fifty species of wildflowers (Table 1) were established on a Sharpsburg silty-clay loam (Typic Argiudoll), with a 6.9 pH, near Mead, Neb. Fortyseven (Table 1) wildflowers were established near Hubbard, Ore., on a Willamette sandy loam (Pachic Ultic Argixeroll) with a 6.6 pH. Both studies used a split-plot design, with herbicide treatment as main plots and wildflowers as subplots. Each treatment consisted of two replicates.

Herbicide treatments included an untreated control and a combination of S-ethyl dipropylthiocarbamate (EPTC) at 2.3 kg·ha-1 and α, α, α -trifluoro-2,6-dinitro-N,N-dipropyl-ptoluidine (trifluralin) at 0.6 kg·ha-1. Applications were made with a boom-sprayer, and treatments were incorporated with a Lily Roterra (Lely Industries, N.V. Maasland, Holland) cultivator immediately after application. Wildflowers were broadcast-seeded at 2 g pure live seed per plot. Irrigation was applied daily at 4 mm·day-1 for 6 weeks after seeding and 13 mm·week-1 thereafter.

In the Nebraska study, tall plains coreopsis (Coreopsis tinctoria Nutt. ) and cosmos (Cosmos bipinnatus Cav.) plants lodged after heavy rains on 15 (33 mm) and 19 July (60 mm) in the herbicide-treated plots but not the control. The lodged plants continued to grow, but remained lodged throughout the growing season. Herbicide-treated Indian blanket (Gaillardia pulchella Foug.) plants had uneven growth and a 2-week bloom initiation delay when compared to the control. After bloom, flowering appeared equal for control and herbicide treatments. About 35% of all species were adversely affected by the herbicide treatment.