Ask Us About PGRs

August 11, 2008 - 07:59

Q Is Configure effective in promoting branching of perennials other than hosta and echinacea?

A We are getting this question a lot this summer. The short answer is “yes.” We have done some screening trials this year with a variety of perennials. We used one rate, 600-ppm Configure (6-BA, Fine Americas, Inc.), on all crops after establishment, about two weeks after the plugs were planted. Some crops were much more responsive to Configure than others, but we have not seen phytotoxicity on any of the crops tested.

Some of the greatest responses have come from crops that are crown-type perennials, like the echinacea and hosta. Heuchera ‘Raspberry Ice’ treated with 600-ppm Configure had 60 percent more basal branches than untreated plants at eight weeks after treatment, with 26 branches on treated plants compared to 16 on untreated plants. Leucanthemum ‘Alaska’ showed slight increase in basal branching with 21 basal branches on treated plants versus 18 on control plants at four weeks after treatment. At the top of the response chart was our test of Gaillardia arista ‘Dazzler’, in which untreated plants had only 23 basal branches at four weeks after treatment, and the plants treated with Configure had 153 branches. I would not expect all of those branches to survive, but even at eight weeks after treatment, the treated plants had nearly 60 percent more flowers than the untreated plants (62 flowers on treated plants versus 39 on the untreated plants).

Lateral branching of some of the more upright plants also increased with Configure. Most notable was Lobelia cardinalis: The treated plants had 13 breaks at four weeks after treatment compared to seven breaks on untreated plants. Lychnis ‘Vesuvius’ increased lateral breaks more than 60 percent — with almost five breaks on treated plants compared to three breaks on untreated plants at six weeks after treatment. In addition, flower number was increased, 18 flowers on treated plants and 13 on control plants. Euphorbia ‘Chameleon’ also showed a moderate increase in lateral breaks.

So yes, there is a lot of potential for improved crop branching and pot fill with Configure. Check the Fine Americas, Inc. website, www.fineamericas.com, for a copy of the Configure supplemental label describing the expanded-use trial recommendations that were recently approved by the EPA. Run your own trials, and watch for more upcoming information on both perennials and greenhouse crops.

Q How does fertilization affect the amount of PGR needed on annuals?

A This has become a common question, and a Texas group recently asked me to give a presentation on the interaction of fertilizers and PGRs. This question is understandable, with the increased need to control expenses. A standard lab project in my greenhouse production class is to have the students grow annuals with a range of fertilizer levels. As the fertilizer rate increases, the plants go from small and chlorotic on the low end to green, tall and better branched at a high rate.

However, as fertilizer is increased to very high levels (two to four times the high rate) the plants become greener and shorter. At these very high fertilizer levels, it is important to manage irrigation and leaching to avoid excessive soluble salt problems. Over the range of fertilizer levels, the larger plants require the most PGR. Low fertilizer and drought stress are old techniques for reducing plant growth. However, these plants often do not have the best quality, are not as attractive at retail and may not grow well after transplanting into beds.

Plants at the very high fertilizer levels can look very good, but managing the high soluble salt levels requires practice and close attention to details. So a grower can either use less fertilizer or more fertilizer to reduce the amount of PGR needed on annuals. However, in most cases, it is easier to grow a good-quality plant using enough fertilizer to make the plant look good and PGRs to control size.

One additional point: Most annuals are grown with fertilizers that have more phosphorous than the plant needs. The phosphorous makes the plants taller and softer. Many growers could reduce their PGR usage by reducing the phosphorous levels in their fertilizer and media.

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