of 20 ppm dip solution, that each bulb absorbs
5 ml of solution, and that the solution is used
until half of it (50 liters) is consumed, it can be
calculated that at least 10,000 bulbs can be
treated, with a cost of slightly more than 0.5
cents per bulb (less than 2 cents per 6” pot
with 3 bulbs). In real practice, it is likely the
final chemical cost per bulb would be lower
than this.
• While this was a large experiment, there was
no repeated dipping into the PGR solutions,
and bulbs were hand selected for the experi
ment, both of which avoids diseased bulbs. In
a commercial setting, thousands of bulbs
would be dipped multiple times into a dipping
solution, increasing the potential of bacterial
disease spread. The effectiveness of pre-plant
PGR bulb dips for hyacinth is established.
Whether it can be safely used in the Indus
try remains to be seen.
• Specific use rates must always be determined
by each grower under local conditions. Growth
temperature, soil, bulb size and many other
factors all affect plant response to any growth
regulator.
Results: Drenches
• All cultivars showed good response to Topflor
drenches in the greenhouse, although Wood
stock was less responsive than the others. In
these experiments, we used 4” pots, and
drenched with 2 ounces (60 ml) within 2-3 days
of placing into the greenhouse.
• For most cultivars, good effects were seen on
stem height and leaf length at bud color/first
open flower stage. The rates used generally
did not delay flowering very much (perhaps by
1-2 days at most).
• Most treatments showed excellent control of
postharvest stem and leaf growth.
• Table 4 gives suggested use rates (in mg/pot)
for the 9 cultivars tested over the past two
years, for each cooling duration. Most cultivars
fall into the 1.5-2 mg/pot range with less cold
(15 weeks of cold), so a very generalized treat
ment of 1.5-2 mg/pot on most cultivars would
be appropriate (if the grower determined it is
necessary) for VD to early Easter flowering.