Ask Us About PGRs

November 13, 2007 - 14:28

Q How can I improve the branching of these new echinacea cultivars?

A We have been working on branching of herbaceous perennials for more than 15 years. Some things have worked better than others, but one of the best success stories is the use of benzyladenine (6-BA) on echinacea. We finally have a labeled and effective 6-BA product for use on perennials: Configure from Fine Americas, Inc. (www.fineamericas.com). The label details its use on hosta, echinacea and Christmas cactus. As I said, the real success story is on echinacea.

We have trialed about six cultivars, and Paul Pilon of Perennial Solutions Consulting (www.perennial-solutions.com) has trialed about that many more (and different) cultivars. We are consistently finding a significant increase in the number of basal branches with rates as low as 300-ppm Configure. With a single spray application of 300-ppm Configure, we more than doubled the number of basal breaks of ‘Double-decker’ going from 1.6 branches per control plant to 4.2 branches on the treated plants at eight weeks after treatment. Results with ‘White Swan’ at eight weeks after treatment were similar with 3.8 branches per control plant and 9.0 branches on plants treated with 300-ppm Configure. Higher rates increased the branching of ‘White Swan’ with 12.8 branches per plant on plants treated with 900-ppm Configure. This really improves pot fill and final plant appearance. Summer-potted plants can be treated in the fall while still actively growing or the following spring after growth resumes. Spring-planted plugs should be well established (2-3 weeks after potting) before treatment. Configure has not been this effective on all perennials, but we have seen no phytotoxicity or distortions on other perennials treated at the label rates. So Configure is definitely a tool that you should add to your PGR toolbox if you are growing perennials.

Q How do I know when I should use a tank mix spray for height control rather than a single product? Also, which chemicals should I combine in a tank mix?

A In simple terms, we use a combination of growth regulators combined in a spray (tank mix) when more control is desired. In cases such as daminozide (B-Nine, Dazide) on bedding plant petunias or paclobutrazol (Bonzi, Piccolo, Paczol) on impatiens, a single product works fine, and we generally can achieve good control with one or two sprays at an average rate. However, with crops like Salvia splendens or marigolds, daminozide often requires multiple applications at high rates; the same is true for paclobutrazol. When the two chemicals are combined, however, there is a synergistic effect, which means that fewer spray applications are needed and the rates do not have to be as high. Thus, the tank mix makes height control easier and better. In cooler months, height control is not too difficult, and a single product often is adequate. But in warmer months, many growers have better success using a tank mix.

The most common growth regulators used as a tank mix are daminozide and cycocel. Both are good products for spray applications, and they have a significant synergistic effect. Daminozide can be combined with paclobutrazol, as mentioned, or uniconazole (Sumagic, Concise) for perennials or other difficult crops. Daminozide can also be combined with A-Rest (ancymidol) and is often used on plugs. Topflor (flurprimidol) is a newer product, but there is no reason that it could not be combined with daminozide. For daminozide, tank mixes with paclobutrazol, uniconazole, A-Rest or Topflor spray application techniques need to be more precise because their activity is more sensitive to variation in spray volume. We generally do not suggest mixing one of these growth regulators with Florel (ethephon) unless the user does extensive trials to understand the interactions. This precaution is because the effects of Florel and the other products are so different. When it comes to drench applications, tank mixes are not used because the strong media active products generally have adequate activity alone.

About The Author

Joyce Latimer is professor and extension specialist for greenhouse crops in the Department of Horticulture, Virginia Tech University, Blacksburg, Va. Jim Barrett is professor of floriculture at the University of Florida, Gainesville, Fla., and GPN’s consulting editor.

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