November December 2023 - 25

CULTURE REPORT
The recommendations that follow are best practices
for successfully growing 'Romantica Ball Gown' from bare
root. Bare root and liners are available for the spring 2024
growing season.
RECEIVING AND HANDLING BARE
ROOT ROSES
For Star Roses and Plants, the harvest and grading
of bare root roses like 'Romantica Ball Gown' begins in
early November and is usually finished by mid-February.
Growers receive bare root rose shipments as early as
December if located in a mild climate or as late as early
April if located in regions like the upper Midwest or
Northeast United States. The extended time between first
harvest date and last shipping date necessitates a plan for
proper storage of the dormant plants.
Bare root roses should be stored in a refrigeration unit
with good ventilation. The optimum storage temperature
for roses is 34° F. If a dormant rose shipment reaches
freezing, it can be carefully salvaged with minimal
detrimental effects by slowly thawing. In this state,
roses should not be watered or quickly thawed in a warm
environment, as this could result in damage or loss. It is
also important to note that dormant roses are sensitive
to ethylene and should never be stored in a refrigeration
unit with fruits or vegetables.
GROWING ENVIRONMENT
There is a wide range of growing environments for
bare-root roses. The most common are inside a heated
greenhouse, directly outside in a mild environment or
in an unheated cold frame. Both indoor and outdoor
locations should have ample light from dawn to dusk and
good air circulation, and be an environment that ensures
the plant material is never in standing water. Cold
frames covered with clear poly will provide the best light
conditions for growing on.
MEDIA
Container media should have 50-70% total porosity
and should average 10-20% air-filled porosity. The
desired pH for growing media is 5.5-6.5. Prior to
planting, prune the canes of Romantica Ball Gown to
4.5 " to 5 " . This pruning will encourage a more uniform
break and a better-finished product. Root pruning is
not recommended unless the roots are too big for the
container, in which case, trim only the minimum and leave
as many fibrous roots as possible.
It is extremely important to keep bare-root plants
from drying out through the entire planting operation.
During planting and spacing, be sure the roses do not
go an extended period without water and that they are
not exposed to
temperatures
below 22° F.
Firming the
soil around the
roots during
potting helps
to mitigate
air pockets
that cause
drying. Herbicide
application is not
recommended
during potting.
BREAKING DORMANCY
As roses break dormancy in the spring, greater
protection is required to prevent or minimize cold
damage. Temperatures below 30° F may require pulling
poly blanket inside a covered hut. Temperature, duration
of low temps, wind and stage of growth are all factors
that should be considered.
Roses that are covered but not in a hut should remain
covered until bud break; then the same procedures for
roses in a covered hut can be followed. Keep these roses
blocked until fully flushed, then space and trim. Keep
protective covering available for low temperature and
wind protection.
Begin to irrigate roses in a growth phase more regularly.
As roses flush, begin regular fungicide applications. Once
roses near finished size, vent aggressively to harden
plants off. Leave clear poly on the hut to protect from low
temperatures, wind and rain events. Clear poly can be
removed from huts at the frost-free date. Ensure plants
are hardened off before removing poly.
IRRIGATION
Roses prefer a thorough watering but do not want " wet
feet. " To reduce disease, avoid leaving foliage wet into
the night. Roses do best when they dry down so they are
slightly moist before the next irrigation. It is important
to make and execute irrigation decisions early in the day,
which gives foliage time to dry and allows the humidity to
be as low as possible at the end of the day.
To learn more about sweating bare root roses,
overwintering roses, crop scheduling, trimming and
pest control, please visit www.starrosesandplants.com/
industry-professionals.
Heidi Mortensen is the Rose Portfolio Manager at Star Roses
and Plants. For more information about 'Romantica Ball Gown'
and other rose varieties, visit starrosesandplants.com.
GREENHOUSE PRODUCT NEWS 25
http://www.starrosesandplants.com/ http://www.starrosesandplants.com
November December 2023

Table of Contents for the Digital Edition of November December 2023
