Rudbeckia: Which Application Method to Choose?

In this video we are going to explore the difference in plant response to Concise, a soil active PGR, applied by different methods using Rudbeckia ‘Goldsturm’. This Rudbeckia is still a major summer flowering perennial for most growers but I get questions on how to manage the height of these plants, especially in quart production. With late spring plugs, these plants begin to stretch as soon as flowers are initiated. All of the experiments presented were performed using liners from the same lot and shipment date (Week 17).

Liner soaks provide early control in a relatively safe application method. So we tested liner soaks of Concise on some of these Rudbeckia ‘Goldsturm’ plugs. For us, in the South, 1 ppm Concise gave moderate control throughout the production period, did not delay flowering, and maintained reasonable plant balance with the quart pot.

Spray applications were also compared to drench applications using plugs from this same lot and shipment date. Liners were potted at the same time as those treated with liner soaks but the treatments were applied one week later. The higher spray concentrations of Concise, 30 to 45 ppm, were required to give adequate control of Rudbeckia ‘Goldsturm’ after flower initiation. The drench applications provided very little control of flower stalk elongation except that the highest rate, 2.0 ppm Concise, improved plant appearance at flowering. Concise concentrations greater than 2.0 ppm would be necessary for good growth regulation of Rudbeckia ‘Goldsturm’.

In summary, Rudbeckia ‘Goldsturm’ is very responsive to Concise (uniconazole). Early application as liner dips improved plant form and flower display in the quart pot program. Liner dip solution concentrations should not exceed 2 ppm unless you really want a late crop. Spray applications of Concise required rates of 30 to 45 ppm to maintain control throughout the production period and provide a reasonable plant balance at flowering. Drench rates greater than 2 ppm would be recommended. While the 2 ppm drench did not provide height control during production, it concentrated the vegetative growth in the pot to provide a more attractive flower display.

The application method and rate you choose will depend on your production methods and conditions as well as the preferences of your markets.

Warning: these Concise (uniconazole) concentrations are considered Southern application rates, so adjust your application rates down for more northern areas.

For more on PGR application methods, see Joyce Latimer’s video entitled “PGR University – Sprays and Liner Soaks”  here
For more on PGR spray applications, see Brian Whipker’s video entitled “Increasing PGR Foliar Spray Efficacy” here
For more on PGR liner soaks, see Brian Whipker’s video entitled “Preplant PGR Liner Soaks” here

Joyce Latimer is an Extension Specialist for Greenhouse Crops at Virginia Tech in Blacksburg, Virginia. Joyce has been evaluating plant growth regulators (PGRs) on herbaceous perennials for over 25 years. Her passion is improving plant quality and ease of production for producers while improving the quality of these plants for the home garden.