INFLUENCE OF PINCHING AND GROWTH RETARDANT ON THE GROWTH OF
LAVENDER (LAVANDULA VERA DC.)
Židovec, Vesna; Vršek, Ines
Department of Ornamental Plants and Landscape Architecture
Faculty of Agriculture
University of Zagreb
Svetošimunska 25
10000 Zagreb
vzidovec@agr.hr
ABSTRACT
The objective of the study was to determine the influence of pinching and/or application of growth
retardant on the growth of lavender (Lavandula vera) cv. Lady grown as a pot plant.
Plants were pinched at the beginning of the growing period and/or treated two times with a
daminozide-based growth retardant (Alar 85), in 0.1% and 0.2% solutions, at an interval of 15 days.
The trial was set up according to the randomized block scheme with five replications.
Plants that were not pinched were taller (27.5%) than pinched and there were no statistically
significant differences between them regardless of the daminozide treatment. A difference at 1% level
was recorded only between untreated plants and plants treated with a 0.2% daminozide solution. Plants
that were not treated with daminozide had the largest number of lateral branches (6.0% more) while
plants treated with a daminozide solution of lower concentration had the smallest number of lateral
branches (2.2% less). Regardless of the daminozide treatment, pinched plants had a smaller number of
lateral branches (2.33% less) compared to plants that were not pinched.
Pinching and growth retardant application influenced the height and the number of lavender lateral
branches. The lowest plants were obtained with pinching and application of a daminozide solution of
lower concentration. Growth retardant application, however, had an adverse effect on the number of
lateral branches.
INTRODUCTION
Lavender (Lavandula vera DC.), semi-shrub originating from the Mediterranean, may reach the height
of 30 to 60 cm. It grows in sunny, dry, rocky habitats on limestone (Hansen and Stahl, 1993; Jelitto
and Schacht, 1995). The whole plants are characterized by their decorativeness, owing to the
evergreen grey-green leaves oppositely distributed along the stem. The flowers appear towards the
beginning of summer in terminal flower spikes of white, pink to dark purple colour, depending on the
cultivar (Armitage, 1997). Apart from their decorative value, they are well known by their use for the
extraction of essential oil applicable in pharmaceutical and cosmetic industries.
For the purpose of expanding the assortment of pot plants of many kinds of perennials, including
lavender, growth retardants are used in cultivation in order to reduce vegetative growth, obtain
compact plants, and encourage flowering.
Daminozide is one among the growth regulators slowing down the biosynthesis of gibberelins and
encouraging flowering (Halevy, 1990). Since it meets the conditions for wide application, it is one of
the most frequently used growth retardants in horticulture (Davis and Andersen, 1989).
Lavender plants are fairly compact and shrubby, but the stem of the inflorescence may elongate
excessively. In growth regulator trials, conducted by Withman et al., 1996 A-Rest and Sumagic
effectively controlled this elongation. Good success was achieved by using one or more applications
of Sumagic in solution of 5-10ppm on 'Munstead' lavender.
For the purpose of obtaining low compact plants, pinching is also performed in some kinds of
ornamental plants. Removal of the shoot apex by decapitation, or pinching out the growth tip, removes
the source of apical dominance and induces out growth of lateral buds.
MATERIAL AND METHODS
The influence of daminozide and/or pinching on the growth of the Lavandula vera DC. cv. Lady,
cultivated in greenhouse, was studied in the period from the first application of daminozide, in April,
until May, when the pot plants were ready for sale. The seed was sown in multipot plates on 19th
January. In the third decade of February, the plants were transplanted into plastic pots with the volume
of 500 ml, into a substrate consisting of TKS 1 and peat. The trial was set up according to the
randomized block scheme with five replications with six combinations and ten plants per combination.
The first combination included control plants cultivated without pinching or daminozide application
(A0P0). The second combination included pinched plants with daminozide application (A0P1). The
third and fourth combination included daminozide application in a 0.1% solution, with the first one not
being pinched (A1P0), and the other one being (A1P1). The fifth and sixth combination included
daminozide application in a 0.2% solution, also without (A2P0) and with (A2P1) pinching.
The plants were pinched above the fully developed apical leaf on 11th April, when the first treatment
using 0.1 and 0.2% daminozide concentrations was also performed, according to the experimental
scheme. The second daminozide treatment followed after two weeks, on 26th April.
Before the beginning of the sale, on 21st May, we measured plant height (cm) and the number of
lateral branches, in order to establish the influence of daminozide and pinching on the growth of
lavender plants.
RESULTS AND DISCUSSION
Plant Height
Variance analysis has shown that among the combinations there is a highly significant difference for
the property of plant height.
Plants treated with a 0.2% daminozide solution were the lowest on the average (3.4% lower than the
average), while those not treated with daminozide were the highest on the average (4.2% higher than
the average).
The highest (8.33cm), as may be seen from Graph 1, were the control plants, which were not pinched
or treated with daminozide. In the case of non-pinched plants, the impact of daminozide increased with
its concentration. Plants treated with daminozide solution of lower concentration (0.1%) had no
statistically significant difference from the control, or from the plants treated by the daminozide
solution of higher concentration (0.2%). The difference at the level of 1% was only between the plants
from the control group and the non-pinched plants treated by the 0.2% daminozide solution.
Non-pinched plants were higher (27.5%) with regard to those pinched. The lowest on the average
(5.42cm) were pinched plants treated with the lower concentration daminozide solution, while the
highest on the average (5.89cm) were pinched plants treated by the 0.2% daminozide solution.
However, among them there was no significant statistical difference, regardless of the daminozide
treatment.
The application of a 0.5% daminozide solution on Aster novi-belgii, in a trial conducted by Whipker
et al. in 1995, caused plant height lowering by 29, i.e 24% respectively, depending on the cultivar. A
significant lowering of the plant height using daminozide was also recorded by Kheshem et al., in
1988, for tomato, and Whipker et al., in 1994, for ornamental kale.
In an experiment with oleander (Nerium oleander L.) conducted by Bañón et al. in 2000, pinched
plants were significantly shorter than non-pinched plants, while CCC was less effective than pinching
in reducing growth.
The Number of Lateral Branches
Variance analysis has shown that among the combinations there is a significant difference for the
property of the number of lateral branches at the level of 1%.
The biggest number of lateral branches (12.53 and 12.36) was found with non-pinched, i.e. pinched
plants not treated with daminozide. This number of lateral branches did not significantly differ from
the number of branches (11.78) of non-pinched plants treated with a 0.2% daminozide solution.
The lowest number (11.29 and 11.51) of lateral branches was recorded with pinched plants treated
with daminozide, regardless of concentration.
In a trial conducted by Yoo YongKweon et al. (1999) on Chrysanthemum zawadskii ssp. naktongense,
pinching caused a lowered number of shoots per plant.
CONCLUSIONS
Pinching and growth retardant application had a considerable influence on the lowering of plant
height. The lowest plants (5.62cm) were obtained with pinching and application of daminozide
regardless of the solution concentration. The biggest number of (12.45) lateral branches was found in
plants not treated with daminozide regardless of pinching. Pinched plants not treated with daminozide
solution (A0P1) were the lowest (5.56cm), with the highest number of lateral branches (12.36).
REFERENCES
Armitage, A. 1997. Herbaceous Perennial Plants. Stipes Publishing, L.L.C., Champaign, Illinois
Bañón, S.; Franco, J.A.; Fernández, J.A.; Ochoa, J.; González-Benavente, A. 2000. Growth
development and leaf colour responses of oleander (Nerium oleander L.) to pinching and chlormequat
chloride treatment
Davis, T.D.; Andersen, A.S. 1989. Growth retardants as aids in adapting new floricultural crops to
pot culture. Acta Horticulturae 252, 77-85
Halevy, A. H., 1990: Recent advances on flowering in horticultural crops. Advances in Horticultural
Science, (4)1:39-43.Hansen, R.; Stahl, F. 1993. Perennials and their garden habitats, Cambridge
Jelitto, L., Schacht, W., 1995. Hardy Herbaceous Perennials. Timber Press, Portland, Oregon
Kheshem, S.A.; Kochan, W.J.; Boe, A.A.; Everson, D.O. 1988: Calcium Translocation and Tomato
Plant and Fruit Responses to Molybdenum and Daminozide. HortScience 23(3): 582-584
Levy, Miriam 1998. Ball RedBook16thEdition, Vic Ball, Batavia, Illinois, USA
Yoo YongKweon; Kang SangWook; Kim HyunKyung 1999. Effects of pinching and daminozide
treatment on growth and flowering of Chrysanthemum zawadskii ssp. naktongense. Journal of the
Korean Society for Horticultural Science 40(5) 598-602
Whipker, B. E., Eddy, R. T., Hammer, A., 1994: Chemical Growth Retardant High Control of
Ornamental Kale. HortScience 29(4): 329
Whipker, B. E., Eddy, R. T., Heraux, Farah, Hammer, A., 1995: Chemical Growth Retardants for
Height Control of Pot Asters. HortScience 30(6): 1309.
Withman, Catherine; Heins, R.; Cameron, A.; Carlon, W. 1996 Rising up Perennials. Greenhouse
Grower. Michigan State University.
Height (cm)
Average Plant Height (cm)
10,00
8,00
6,00
4,00
2,00
0,00
8,33
7,91
5,56
A0P0
A0P1
7,00
5,42
A1P0
A1P1
A2P0
5,89
A2P1
Treatments
Average Plant Height (cm)
Graph 1: Average Plant Height
A0P0 = control - plants that were neither pinched nor treated with daminozide
A0P1 = pinched plants without daminozide treatment
A1P0 = non-pinched plants treated with 0.1% solution of daminozide
A1P1 = pinched plants treated with 0.1% solution of daminozide
A2P0 = non-pinched plants treated with 0.2% solution of daminozide
A2P1 = pinched plants treated with 0.2% solution of daminozide
Number
Average Number of Lateral Branches
13,00
12,50
12,00
11,50
11,00
10,50
12,53
12,36
11,78
11,69
11,29
A0P0
A0P1
A1P0
A1P1
A2P0
11,51
A2P1
Treatments
Average Number of Lateral Branches
Graph 2: Average Number of Lateral Branches
A0P0 = control - plants that were neither pinched nor treated with daminozide
A0P1 = pinched plants without daminozide treatment
A1P0 = non-pinched plants treated with 0.1% solution of daminozide
A1P1 = pinched plants treated with 0.1% solution of daminozide
A2P0 = non-pinched plants treated with 0.2% solution of daminozide
A2P1 = pinched plants treated with 0.2% solution of daminozide