Four Star Culture Guide - 2019 - 85

HYDRANGEA ARBORESCENS
and PANICULATA CONTINUED
H. Arborescens
The PGR regimen starts in spring, the second season after
potting your liners. While dormant, trim plants to 4 - 6"
(10 - 15.2cm) above pot level. After they flush out and put
on two nodes of new growth, applications should begin. We
recommend using daminozide such as B-Nine®, with a starting
rate of 5,000ppm - 7,000ppm. If a stronger solution is required
(see below), tank mix with chlormequat chloride such as
Cycocel® at 500ppm - 1,500ppm.

PEST and DISEASE MANAGEMENT
Aphids and Spider Mites are the most prevalent insect pests
associated with Hydrangea. Scout and spray preventatively in
April/May to prevent outbreaks in June and July when Spider
Mites are more actively growing. We recommend implementing
a good IPM program as well as early releases of Biological
Control to help aid in the control of insect populations.
Avoid using M-Pede® on Hydrangea because it can cause
phytotoxicity.

The solution should be applied to the foliage and stems - do not
use as a drench. Spray for even coverage, until leaves begin to
drip the solution. It's best to spray on cloudy days, though early
morning or late evening sprays are also acceptable. The longer
the foliage stays wet from the solution, the more effective it
will be, so avoid applying when sun or heat would dry it too
quickly. High light intensity can also scorch recently sprayed
leaves.

OTHER TIPS
Any surplus 1 gallon containers can easily be bumped into
3 gallon containers in the summer for the following season's
spring sales.

Multiple applications are recommended for best results,
though it is difficult to give an exact number or frequency. Light,
temperature, and fertility all influence when you will need to
spray your crop. When plants have put on two nodes of new
growth, spray with the PGR solution again. Light green new
growth and longer internodes are additional cues that another
application is required.

Soil pH does not affect bloom color on Paniculatas.

Provide adequate air circulation so that high humidity levels do
not limit pH uptake causing cupping and/or tip burn on newly
expanding leaves.
Hydrangea paniculata is the only Hydrangea that can be pruned
into a tree form.

Continue to spray plants in this manner until flower buds appear
in the flush of new growth. If the weather warms considerably
during the process, consider using the stronger mix described
above. Important: using the daminozide + chlormequat
mix can greatly slow plant growth and potentially affect
production schedules. Trial small groups of plants before
applying to entire crop. Stop applying the PGR solution when
the flush of new growth reveals flower buds. Plants may be
shipped at this point or held until they show some color.
Never apply PGRs when the plant has flower buds the size of a
dime or larger. Doing so will result in uneven blooming/smaller
flowers.

The rates and chemicals listed are based on our southeast Michigan growing conditions, and are not recommended for nationwide application.
Please adjust the rates and spray applications to your location and facility.

Four Star Culture Guide - 2019

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