June 2022 - 30

YOUNG PLANTS & LIGHTING
For one, most LED screw-in
PETUNIA 'WAVE PURPLE'
Short day
Feit
A19 Plant
Grow Light
Lamp
TotalGrow
Pure Flowering
Lamp
GE
Photoperiodic
Lamp
Philips
Flowering
fixtures for home or office use are
not designed for high-humidity, wet
and high temperature conditions
as can be seen in Figure 1. In this
example, moisture has penetrated
and accumulated inside the lamp,
rendering it useless and unsafe.
Additionally, different lamps provide
different wavelengths, which can
influence time to flower and finished
quality of your crop. In this article,
we will focus on the flowering
and growth responses of several
facultative and obligate LDPs to lowintensity
screw-in LEDs providing
different light qualities.
DIANTHUS 'ROCKIN RED'
Short day
Feit
A19 Plant
Grow Light
Lamp
TotalGrow
Pure Flowering
Lamp
GE
Photoperiodic
Lamp
Philips
Flowering
WHAT DID WE FIND?
We grew calibrachoa 'Kabloom
Pink' (Calibrachoa x hybrida),
dianthus 'Rockin Red' (Dianthus
chinensis x barbatus), ornamental
oregano 'Kirigami' (Origanum x
hybrida), petunia 'Wave Carmine',
petunia 'Wave Purple' (Petunia
x hybrida), snapdragon 'Liberty
Classic Yellow', and snapdragon
'Solstice Yellow' (Antirrhinum majus)
under five different treatments,
consisting of a nine-hour short day
(SD) created by closing opaque
black cloth at 5 p.m. and opening it
the following morning at 8 a.m., or
nine-hour SDs with various screw-in
horticultural LED lamps providing
2 to 3 µmol∙m-2
∙s-1
SNAPDRAGON
Short day
'LIBERTY CLASSIC YELLOW'
TotalGrow
Feit
A19 Plant
Grow Light
Lamp
Pure Flowering
Lamp
GE
Photoperiodic
Lamp
Philips
Flowering
during a fourFigure
3. (A) Flowering responses of petunia 'Wave Purple', (B) snapdragon
'Liberty Classic Yellow', and (C) dianthus 'Rockin Red' placed under a 9-h short
day, or under 4-h night interruption lighting from 10 p.m. to 2 a.m. from a
9-W non-dimmable A19 LED; Feit Electric, 16-W TotalGrow pure flowering 200
lamp, 10-W GE Arize Greenhouse Pro photoperiodic LED lamps or 13-W Philips
GreenPower LED flowering lamps.
30 JUNE 2022 GPNMAG.COM
hour NI from 10 p.m. to 2 a.m.
LED treatments consisted of 9-W
non-dimmable plant grow lights
(A19 LED; Feit Electric, Pico Rivera,
California), 16-W TotalGrow pure
flowering 200 lamps (TG1B-1104
Bulb; Venntis Technologies LLC,
Holland, Michigan), 10-W Arize
Greenhouse Pro photoperiodic
LED lamps (General Electric
Lighting; Cleveland, Ohio), or 13-W
GreenPower LED flowering lamps
(DR/W/FR; Philips, Eindhoven,
The Netherlands) (Figure 2). The
Feit, TotalGrow, Philips, and GE
lamps provided a light ratio (%) of
18:27:46:9, 1:2:40:57, 8:13:35:44,
and 5:18:47:30 of blue, green, red,
and far-red light, respectively. The
R:FR ratios of the treatments were
5.1, 0.7, 1.6, and 0.8, respectively.
Plants were monitored daily for
the presence of visible flower buds
and first open flowers (OF). On the
date of OF, the number of nodes
below the first OF were recorded
for each plant. Additionally, plant
height and total number of initiated
inflorescences were recorded.
FLOWERING RESPONSES
All of the LED lamps we tested,
regardless of emission spectrum,
were successful at promoting
flowering of the facilitative
and obligate LDPs tested. For
calibrachoa, oregano, petunia
'Wave Purple', and snapdragon
'Solstice Yellow', the Philips and GE
lamps slightly hastened flowering
(1-3 days) compared to the other
photoperiodic lighting treatments.
Flowering of dianthus, petunia 'Wave
Carmine', and snapdragon 'Liberty
Classic Yellow' was hastened by 6,
11, and 7 days, respectively, when
grown under the Philips lamps
compared to the Feit lamps (Figure
3). Time to flower was similar for
dianthus and snapdragon 'Liberty
Classic Yellow' grown under all
photoperiodic lighting treatments
except the Feit lamps (Figure 3).
Petunia 'Wave Carmine' flowered
4 and 8 days faster when grown
under the Philips compared to
the GE or TotalGrow lamps. While
calibrachoa, oregano, and petunia
'Wave Carmine' did not flower under
SDs, photoperiodic lighting hastened
flowering of dianthus, petunia 'Wave
Purple', snapdragon 'Liberty Classic
Yellow' and 'Solstice Yellow' by up
to 7, 23, 17 and 8 days, respectively
(Figure 3).
Calibrachoa, dianthus, oregano,
petunia 'Wave Purple', and
snapdragon 'Solstice Yellow'
had a similar number of nodes
below the first OF regardless of
treatment. Petunia 'Wave Carmine'
and snapdragon 'Liberty Classic
Yellow' grown under Philips lamps
had seven and eight fewer nodes,
respectively, than those grown under
the Feit lamps. Height of dianthus,
oregano and snapdragon were not
commercially different between
photoperiodic lighting treatments.
Moreover, oregano and
snapdragon had a similar number
of initiated inflorescences at OF
regardless of the photoperiodic
lighting treatment they were grown
under. However, dianthus grown
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June 2022

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