October 2023 - 12

PGRs
can be useful for potted plants such as streptocarpus.
Finally, fruit ripening can also be promoted with ethephon
and sprays can be made to ornamental peppers to enhance
the rate of coloration.
The most important thing to keep in mind when using
ethephon is its multi-faceted effects. While controlling
height, aborting flowers, ripening fruits can all be good
things, they may not be at the same time. For example,
while an application of ethephon may be used with the goal
of controlling height and increasing branching, it may also
negatively affect flowering.
improved stem length, and GA applications can help
promote desirable elongation that increases stem value. It
can also be used to help improve flowering of several cut
flower species including statice and calla lilies. Though it
was historically used to hasten flowering of cyclamen, this is
no longer necessary with modern cultivars.
GIBBERELLIC ACID + BENZYLADENINE
The combination of GA4+7
and BA7
, commercially available
as Fascination or Fresco, has several uses in potted flowering
and foliage plant production. First, using GA+BA to overcome
excessive growth regulation or promote growth is more
advisable than using GA alone for potted flowering plants.
Since we are almost always trying to inhibit stem
elongation of potted plants, the more measured growth
promotion resulting from GA+BA is more desirable than
potentially more potent promotion from straight GA. Timing
of the GA+BA application can also influence results. For
example, to promote plant height in poinsettia it is best
used before short days start, whereas to promote bract
development and expansion it is better applied during the
last few weeks of finishing.
Not all growth retardants can be applied in the same way. Those
PGRs that are taken up by roots (including ancymidol, flurprimidol,
paclobutrazol, and uniconazole) can be used for application
methods beyond sprays, such as the bulb soaks used to treat
these Easter lilies before planting.
Although ethephon has traditionally been applied as a
spray, research has shown that it is also effective when
applied as a drench. Up until now, no commercial ethephon
product had been labeled for drench applications. However,
in early 2024 an updated label for Collate is due out that will
include drench applications.
BENZYLADENINE
Benzyladenine (BA) is a cytokinin available
commercially as Configure. While cytokinins influence a
variety of plant processes, we use it in potted floriculture
crop production to improve holiday cactus production.
When used during the vegetative phase of production it
increases branching and phylloclade number, and when
used during inductive short days or cool temperatures it
increases flower number. It can also be used to increase
the number of offsets in containerized for rosette
succulent houseplants such as Eschevaria.
GIBBERELLIC ACID
While we have already discussed those active ingredients
that suppress GA production, there is a place in floriculture
for applying GA to crops. Cut flowers can benefit from
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OCTOBER 2023 GPNMAG.COM
Premature flowering can be a problem for potted plants with
longer production times. There are several uses for ethephon,
and inhibiting flowering is among them.
In addition to growth promotion, GA+BA can also be
used to inhibit leaf senescence, or lower-leaf yellowing, on
potted crops such as lilies during the early season (before
budding) or late in production <2 weeks before shipping).
When being used to inhibit leaf senescence, only apply to
the lower leaves that are at risk of senescing, not the whole
plant; unwanted growth promotion could occur if the entire
plant is treated.
Chris Curry is an associate professor in the Department of
Horticulture at Iowa State University. For more information
email ccurrey@iastate.edu.
http://www.GPNMAG.COM
October 2023

Table of Contents for the Digital Edition of October 2023
