triazol-1-yl-penten-3-ol) is labelled forapplication as a foliar spray or as a root-medium drench (Uniroyal ChemicalCo., Middlebury, Conn.). Granular(Ruter, 1992) and spike formulations(Barrett et al., 1994; Deneke andKeever, 1992) are also effective meth-ods for applying paclobutrazol. Thepurpose of this study was to evaluatethe effectiveness of paclobutrazol ap-plied as a foliar spray, root-mediumdrench, or impregnated spike on thegrowth control and flowering of NewPaclobutrazolApplicationMethodInfluences

Growth andFlowering ofNew GoldLantana

John M. Ruter1

Additional index words. Lantanacamara L., Bonzi, growth regulator

Summary. Paclobutrazol was appliedas a foliar spray, root-medium drench,and impregnated spike to New Goldlantana grown in 2.8-liter pots. Plantswere treated 14 June 1993 at rates of0, 0.5, and 1.0 mg a.i. paclobutrazol/pot and were harvested 27 July 1993when control plants required furtherpruning. Impregnated spikes reducedplant size and flowering to a greaterdegree than spray applications.Drenches reduced root dry weight andbiomass compared to spray applica-tions. Plants treated with 0.5 and 1.0mg a.i. paclobutrazol/pot were notdifferent in regards to plant growthand flowering. Compared to non-treated controls, plants treated with

1Associate professor, University of Georgia, Departmentof Horticulture, Coastal Plain Experiment Station,Tifton, GA 31793.Funding for this research was provided by UniroyalChemical Company. The cost of publishing this paper wasdefrayed in part by payment of page charges. Underpostal regulations, this paper therefore must be herebymarked advertisement solely to indicate this fact.

HortTechnology Jan./Mar. 1996 6(1)paclobutrazol had a reduced growthindex, decreased shoot and root dryweight, and fewer flowers with openflorets. All plants in the study weremarketable, even though growthcontrol was considered excessive.Lower rates than used in this studyshould be considered for controllinggrowth. These results suggest thatimpregnated spike formulations ofpaclobutrazol may control plantgrowth in pine bark-based media.

s h r u b l a n t a n a ( L a n t a n acamara L.) is a vigorouslygrowing small shrub, which of-ten is used as an annual in the easternUnited States for its continuous bloomperiod during the summer. Whengrown in containers, lantana requiresfrequent pruning to maintain plantshape and marketability. New Gold isa prostrate form that produces manygolden-yellow flowers. The popularityof New Gold lantana has increased,and the plant recently was selected bythe Georgia Plant Selections Commit-tee as a Gold Medal winner for 1995(Jim Midcap, personal communica-

tion).

Paclobutrazol ((2 RS, 3 RS )-l-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-

Table 1. Effect of paclobutrazol application methocamara New Gold in 2.8-liter containers. Data amg a.i./pot.Gold lantana.

Materials and methodsResearch was conducted at Wight

Nurseries in Cairo, Ga. Fifty-four plantswere grown in 2.8-liter pots and prunedto a height of 12 cm on 13 June 1993.The potting medium consisted of a 4pine bark : 1 sand (v/v) mixture. Liq-uid fertilizer (10N1.5P8.5K) wasapplied with each irrigation at the rateof 100 mg N/liter. Plants were grownin full sun and irrigated as needed at 20mm/irrigation using solid-set sprin-klers.

Paclobutrazol was applied on 14June 1993 at the rates of 0, 0.5, or 1.0mg a.i./pot as a foliar spray, mediumdrench, or impregnated spike. Foliarsprays (5 ml/plant) and mediumdrenches (120 ml/plant applied to thesurface of the container medium) wereapplied using Bonzi (1280 mg a.i./liter, Uniroyal Chemical Co. ). Spikes(0.25 mg a.i./spike) were identical toJobe fertilizer spikes (Weatherly Con-sumer Products, Lexington, Ky.) withpaclobutrazol impregnated in thespikes instead of fertilizer. Two or fourspikes were positioned vertically in thecontainer medium with the top of thespike even with the surface of the con-tainer medium. Spikes were placedequidistant from each other on oppo-site sides of the plant about 5 cm from

d on the growth and flowering of Lantanavevaged over application rates of 0.5 and 1.019

hi

rTable 2. Effect of paclobutrazol application metof Lantana camara New Gold in 2.8-liter conta0.5 and 1.0 mg a.i./pot.

ZBiomass: shoot dry weight + root dry weight.YGrowth index: [(height + width 1 + width 2)/3].NS,*Nonsignificant or significant P 0.05. Mean separates of 0.5 and 1.0 mg a.i./pot by Dunnett's0.05.

the edge of the pot. The experimentwas a completely randomized three three factorial with six plants per treat-ment combination.

The experiment was terminated27 July 1993 when nontreated controlplants required pruning to remainmarketable. Measurements includedwere growth index [(height + width 1+ width 2 (perpendicular to width1))/3], shoot dry weight, root dryweight, number of flower heads, andnumber of heads with open florets.Data were evaluated by analysis ofvariance. Mean separations were by

Wailer-Duncan K ratio and Dunnettst tests where appropriate. Since therewere no interactions between applica-tion method and rate of paclobutrazolapplication, only main effects are pre-sented.

Results and discussionFor all measurements, spike ap-

plications of paclobutrazol resulted inreduced plant growth and floweringcompared to sprays (Table 1). Growthindices were reduced 22%, shoot dryweight decreased 19%, root dry weight50%, biomass 33%, number of flowerheads 48%, and number of flower headswith open florets 41% when plantswere treated with spikes compared tospray applications. Drench applicationsof paclobutrazol were not differentfrom spikes for root dry weight, biom-ass, and number of flower heads withopen florets. Compared to spray appli-cations, drenches resulted in reducedroot dry weight and biomass of 32%

20od and treatment on the growth and floweringners. Data averaged over application rates of

ation of nontreated contols with data pooled over

and 18%, respectively (Table 1).For application rate, there were

no differences between plants treatedwith 0.5 and 1.0 mg a.i./pot, so ratedata were combined and compared tonontreated control plants. For sprayapplications, paclobutrazol reduced thegrowth index by 24%, shoot dry weightby 37%, root dry weight by 55%, bio-mass by 46%, number of flower headsby 26%, and number of flowers withopen florets by 38% (Table 2). Withdrench applications, treatment withpaclobutrazol reduced the growth in-dex by 21%, shoot dry weight by 26%,

root dry weight by 77%, biomass by47%, and number of flowers with openflorets by 21% (Table 2). The totalnumber of flower heads was not re-duced by drench treatments with pa-clobutrazol. Spike applications of pa-clobutrazol reduced all plant growthand flowering by >62% (Table 2).

All plants treated with paclobutra-zol had darker green foliage and werevery compact due to internode short-ening compared to nontreated plants.However, no leaf distortion was notedon plants treated with paclobutrazol.Growth reductions were consideredexcessive by the grower in this study,although plants remained in market-able condition. Lower rates of pa-clobutrazol (