Four Star Culture Guide - 2019 - 83

HIBISCUS

(Rose of Sharon)
ZONE HARDINESS 5 - 9
NUTRITION
pH: 5.8 - 6.2
EC: (2:1 extraction method) 1.0 - 2.0
Moderate to high fertilization is recommended. 200ppm -
300ppm N. Hibiscus are very heavy feeders. Light colored
foliage coloration and yellowing of veins is an indication for
underfeeding.
TEMPERATURE for forcing from liners
Forcing/Growing on: 60 F Night - 72 F Day
Holding: 40 Night - 50 F Day
Once plants reach a saleable size, they can be moved to a
frost protected open environment with good air movement.
Crops can be slow to break dormancy in spring until warmer
temperatures return.
WATERING
Moderate to Moist: Best if planted in well-drained soil. Rose
of Sharon does not like to be extremely wet or dry. Water
thoroughly without oversaturating, keep moist during root
development, allow soil surface to dry before watering after the
crop is rooted to the edge of the pot.
TIMING
28 Liner to True 1 Gallon: 12 - 14 weeks with one plug per
container. A typical planting date for spring forcing would be
Week 10 for finishing in Week 22 - 24. If a larger size is desired,
we recommend planting these in the fall and doing additional
bulking prior to dormancy. Planting a 28 count liner into a 2 - 3
gallon and bulking in the summer is also a great way to finish a
larger high-quality spring crop.
Quick Turn™ Liner to True 1 Gallon: 8 - 10 weeks with one
plug per container. A typical planting date for spring forcing
would be Week 12 for finishing in Week 22.
Quick Turn Liner to 2 - 3 Gallon: Planting a Quick Turn liner
into a 2 - 3 gallon container and bulking in the fall is also a
great way to finish a larger high-quality spring crop.
VERNALIZATION
A cold treatment is required on Hibiscus (Rose of Sharon).

PLANTING
Hibiscus perform best when planted in a well-drained, porous
growing medium.
When growing Shrubs, we recommend using an aged or
composted pine bark-based media as opposed to an annual
growing mix that traditionally tend to be heavier in peat. Bark
adds weight and stability to the growing mix and tends not to
compress and shrink over time, thus adding the longevity that
can be needed on long-term crops such as Shrubs.
LIGHT/LIGHTING
During early spring forcing, plants should be given as much
light as possible. Long days induce flowering. Crops should
be spaced such that they do not shade each other. Unspaced
plants can stretch, require additional pruning, and lead to an
undesirable look on the retail bench.
TRIMMING/PINCHING
Hibiscus benefit from frequent light pruning rather than hard
pruning. A hard shearing can shut down growth for 3 - 4
weeks.
GROWTH REGULATORS
Trimming and pruning is used mostly on Hibiscus (Rose of
Sharon) to control plant height. Cultural practices such as good
air movement in an open environment can help control plant
height and assist in finishing a high-quality crop.
PEST and DISEASE MANAGEMENT
Aphids and Whiteflies are the most prevalent insects
associated with Hibiscus. Scout and spray preventatively
in April and May to prevent outbreaks in June and July
when insects 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.
SPECIAL NOTES
When growing larger containers such as 3 gallons, it is best to
bulk them in the summer/fall the year before they are to be sold.
This allows additional root growth as well as additional pruning.
Any surplus 1 gallon containers can easily be bumped into 3
gallon containers in the fall or early spring for spring sales.

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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