Growth Regulation of Russian Sage During Greenhouse and Nursery Production

Abstract

Abstract Growth response of Perovskia atriplicifolia (Russian sage) treated with several plant growth retardants (PGRs) was determined under three production regimes: 1) small plants in 10 cm (4 in) pots grown in a greenhouse and half transplanted into the landscape at 6 weeks after treatment (WAT), and 2) large plants grown in 3.8 liter (#1) pots in a greenhouse or 3) in an outdoor nursery. Plants in 3.8 liter (#1) pots were not transplanted into the landscape. Treatments included Cutless at 50, 100 and 150 ppm; Sumagic at 20, 40 and 60 ppm; B-Nine/Cycocel tank mixes at 2,500/1,500, 5,000/1,500 and 7,500/1,500 ppm; Pistill at 500 and 1,000 ppm; and a non-treated control. All PGRs controlled plant growth through 6 WAT in the greenhouse and 2 weeks after planting. At this time (8 WAT), plants treated with the most effective rate of Cutless (150 ppm), Sumagic (20, 40, or 60 ppm), B-Nine/Cycocel tank mixes (5,000 ppm/1,500 ppm), and Pistill (500 or 1,000 ppm) were 32%, 32%, 25%, and 32% smaller in 10 cm (4 in) pots and 21%, 22%, 22%, and 16% smaller in 3.8 liter (#1) pots, respectively, compared to non-treated controls. Treatment effects were non-significant by 4 weeks after plants grown in the greenhouse in 10 cm (4 in) pots for 6 weeks were transplanted into the landscape (10 WAT). Plants in 3.8 liter (#1) pots in the greenhouse were significantly smaller, excluding those treated with Pistill, than non-treated controls at 12 WAT; at this time, the most effective rate of Cutless (150 ppm), Sumagic (40 ppm), and B-Nine/Cycocel tank mixes (5,000 ppm/1,500 ppm) suppressed growth 21%, 23%, and 26%, respectively. For 3.8 liter (#1) pots in the nursery, Cutless suppressed growth 5–11% at 2 WAT only, and the most effective rate of Sumagic (60 ppm) reduced growth 7% at 4 WAT, but not thereafter. The most effective rates of B-Nine/Cycocel (7,500 ppm/1,500 ppm) and Pistill (1,000 ppm) suppressed growth 13% and 10%, respectively, at 8 WAT. Results suggest that PGR effectiveness is less outdoors under nursery conditions than in the greenhouse, particularly for Cutless and Sumagic. The duration and magnitude of B-Nine/Cycocel treatment effects suggest that this PGR combination may provide the most effective growth control of Russian sage under nursery conditions.