October 2020 - 34

CULTURE REPORT
Primula Princessa Series
This new series will incite plant lovers' memories of spring and cheerfulness.
BY KEN HARR
S
akata Ornamentals has introduced a new, extra-large flowering
Primula acaulis that even by primula standards is astonishingly
striking. The delicate strength of Princessa primula showcases
brilliant flowers with thick petals shining brightly against its dark green
foliage. With six colors - Scarlet, Rose, Golden, Pink, White and Blue - all
flowering uniformly, Princessa will absolutely stop flower consumers to see
closer, to pick up, to touch, to marvel at its extraordinary beauty.
INNOVATIVE FLOWER BREEDING
For several decades, Sakata Ornamentals' R&D plant breeders have
become known for their unique contributions to the industry. Sakata's
Primula acaulis series, Danova, Super Nova, Danessa and others have
become synonymous with success and profitability for growers. The new
Princessa primula will certainly continue the high standards that have
been set. With its ability to flower profusely with little to no vernalization,
combined with its exceptional durability in shipping and handling, growers
will love producing, finishing and shipping Princessa and watch them sell
quickly at retail stores.
GROWING AND PRODUCTION DETAILS
For a successful crop, follow the guidelines below.
* Recommended media pH is 5.8 to 6.2. Monitor pH closely; levels above
6.2 may result in iron chlorosis.
* Fertilize plugs with 100 ppm of nitrogen with calcium nitrate-based
fertilizer. Maintain soil EC levels between 0.26 and 0.75.
* Generally, primula are not bothered by insects, but problems with
fungus gnats and shore flies are common during the germination and
plug stages.
* Primula require cool temperatures and high humidity to produce highquality
plants, which could cause the development of Botrytis.
Good sanitation, maintaining proper moisture management levels,
and good air movement will help prevent Botrytis.
GERMINATION
Two important factors are important at this stage: moisture management
and soil temperature.
Maintain moisture levels of 4 to 5 (wet to saturated) until radicle
emergence. Dry down to levels 3 and 4 after cotyledons have unfolded and
lower humidity levels to ~40%. Light is needed for germination but a light
vermiculite cover to help maintain moisture around the seeds can be used.
Optimal germination temperature is 64 to 68º F. Temperatures above
68º F may reduce total emergence.
GROWING ON
After the first true leaves have formed, target average daily temperatures
(ADT) at 62 to 64º F and soil moisture levels at 3 (moist), and lower
humidity levels. Do not allow plants to dry down or flag in the early stages
of bulking up, but do not over-water as well.
Maintain soil pH at 5.5 to 5.8 and EC at 0.75 to 1.0 utilizing calciumnitrate
based feeds.
TRANSPLANT TO FINISH
Maintain day/night temperatures of 61 to 65º F to promote vegetative
growth and plant bulking.
Recommended light levels are 1,700 to 2,000 foot-candles with a
maximum of 3,000 foot-candles.
Maintain pH at 5.5 to 5.8 and soil EC at 1.0 to 1.2. Increasing potassium
will promote higher bud counts and compact plants. If pH levels are above
6.3, treat plants with acid-based fertilizers, or utilize pH adjusted water. If
needed, supplement with chelated iron (EDDHA) at 4 ounces/100 gallons.
If plants seem to stall during higher temperature days, supplement with
21-7-7 at 100 to 125 ppm to stimulate growth. Supplement magnesium
sulfate at 16 ounces/100 gallons to avoid magnesium deficiency.
FLOWER INITIATION
Princessa is a medium-early Primula acaulis. At the six to 10 leaf
stage, with a well-established root system, the plants are receptive
to bud initiation. Princessa requires less vernalization than other
commercial acaulis varieties to initiate flowering, with the optimal
temperature range targeted at 50 to 59º F.
Primula Princessa is destined to become the hot new novelty primula
on the market. Extra-large, radiant colored blooms will absolutely amaze
flower buyers. This is a primula that growers must try; the results will be
especially rewarded with retailers and customers calling for more. In the
Pacific Northwest, decorative pots on a cloud-covered winter's porch; in
the South, accenting winter flower beds or in decorated entryways; and in
the Midwest and East as a bright, cheerful reminder that spring is not that
far away, Princessa primula will show its strength and beauty in a myriad of
different and distinctive ways.
Ken Harr is a product technical manager with Sakata Ornamentals. He can be
reached at kharr@sakata.com.
34 OCTOBER 2020 GPNMAG.COM
http://www.GPNMAG.COM
October 2020

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