86 October 2005 • Greenhouse Grower

by MATTHEW BLANCHARD, ROBERTO LOPEZ, ERIK RUNKLE and

YIN-TUNG WANG

IN the previous three articles onpotted phalaenopsis orchids, wedescribed the many appealing at-tributes of phalaenopsis and dis-

cussed the important production factorsinvolved in producing a flowering crop.In the conclusion of our four part series,we will put this information togetherand provide a simplified productionschedule that can be implemented intoyour greenhouse operation.

Phalaenopsis production can be di-vided into three phases:

• Phase 1. Vegetative cultivation athigh temperatures of 82°F to 90°F(28°C to 32°C).

• Phase 2. Spike induction at lowday temperatures of 63°F to 77°F (17°Cto 25°C).

• Phase 3. Finishing at 63°F to 79°F(17°C to 26°C).

Depending on your facilities and cli-mate, the production of flowering pot-ted phalaenopsis can involve all threeof these phases or may be limited toonly one or two phases. As discussedin the July 2005 issue of GreenhouseGrower, one option for growers is topurchase non-flowering, immatureplants that require additional vegeta-tive growth before cooling and spike

induction. A grower who chooses thisoption will use all three productionphases. Alternatively, the vegetativephase can be omitted by purchasingmature plants of flowering size that areready for the cooling phase. Growerswho adopt this production strategypurchase plants that can be induced tospike soon after arrival and then fin-ished for their market date. In some cir-cumstances, plants with a visible spikethat have already received cooling canbe purchased. These plants are termed

“prespiked” and are finished bythe grower for flowering.

With these options for pur-chasing plant material in mind,let’s now discuss a simple sched-ule for producing a crop of flow-ering phalaenopsis.

Phase 1: VegetativeCultivation

A grower who purchasesyoung plants will begin productionof phalaenopsis with vegetative cul-

tivation. For the large-flowered hy-brids and clones, this plant materialgenerally has an average leaf span of ≤10 inches (25 centimeters) and will notflower uniformly without additionalgrowth.

Depending on the source, youngplants may need to be potted or trans-planted into a larger container. Plantmaterial with an average leaf span of 8inches (20 centimeters) is often trans-planted into 5-inch (12-centimeter)pots. Spacing depends on plant sizeand grower preference, but early inthe production phase, plants can bespaced pot-to-pot. Following trans-planting, several irrigations may benecessary to sufficiently moisten thesubstrate, depending on the environ-mental conditions and medium com-position. Due to the low water-hold-ing capacity of fresh bark, newlytransplanted material will need to befrequently checked for watering untilthe medium begins to hold moremoisture. Media with high water-

P R O D U C T I O NO R C H I D S

In the final article of this four-part series, find out how to cash in on orchids, the

second hottest potted flowering plant in the United States.

The Orchid Grower

Temperature °F (°C) Time from visible spike to flower (days)

57 (14) 26663 (17) 13368 (20) 8773 (23) 6876 (26) 52

Table 1.

Phalaenopsis placed into decorative terra cotta pots and ready for shipping to a retail store.

The effect of average daily temperature onthe average time from visible spike to flowerin several phalaenopsis hybrids grown atMichigan State University.

87 October 2005 • Greenhouse Grower

holding capacities need less frequentwatering. Some growers place a thinlayer of fabric (e.g., remay cloth) overbenches for one to two weeks afterplanting bare-root plants to create dif-fuse light levels less than 1,000 foot-candles (200 µmol·m-2·s-1) and to in-crease humidity. This strategy helps tominimize plant stress and reduce plantloss after planting.

Young plants are grown at hightemperatures in the range of 82°F to90°F (28°C to 32°C) to promote vegeta-tive growth and inhibit flowering. Ifenvironmental conditions are favor-able, plants with a leaf span of 4 to 5inches require approximately 22 to 27weeks to reach flowering size. Thisduration depends on temperature, theinitial leaf span, fertility and the sizedesired before the induction of flower-ing. On average, a new leaf will formevery seven to 10 weeks. When im-porting mature bare-root plant materi-al from overseas, providing four to six

weeks of growth in a warm environ-ment after planting will be beneficialfor rooting and subsequent flowering.

Remember to monitor light levelsand adjust shading to provide be-tween 500 and 1,500 footcandles (100to 300 µmol·m-2·s-1) of diffused light atcanopy level. Plants should be spacedas necessary to minimize leaf overlapand allow for adequate air circulation.During spacing, it is also a good ideato sort plants according to leaf span.Plants with a small leaf span will re-quire additional time before the onsetof the cooling phase.

Phase 2: CoolingWhen plants have four to six leaves

and a minimum leaf span of 10 inches(25 cm), the cooling phase can begin toinduce spiking. A grower that pur-chases mature potted plants maybegin with this phase of production.Plants can be cooled at temperaturesin the range of 63°F to 77°F (17°C to25°C) for approximately four to sixweeks. In most phalaenopsis hybrids,a spike (the flowering stem) will usu-ally become visible after three or fourweeks of cooling. However, longer du-rations may be required for some

P R O D U C T I O NO R C H I D S

Production PhaseUnits Vegetative Growth Cooling Finishing

Duration weeks 22 to 27 4 to 6 8 to 15Temperature °F 82 to 90 63 to 77 63 to 79

°C 28 to 32 17 to 25 17 to 26Light intensity footcandles 500 to 1,500 500 to 1,500 500 to 1,500

mol•m-2•s-1 100 to 300 100 to 300 100 to 300Pot size inch 5 5 5

cm 12 12 12

Table 2.A simplified schedule for the production of flowering potted phalaenopsis orchids in 5-inch (12-cm) pots.

For Details Circle No. 52 on Postcard or at www.greenhousegrower.com For Details Circle No. 3 on Postcard

88 October 2005 • Greenhouse Grower

hybrids or when plant material is moderately small.Cooling may take place in the same greenhouse section as

the vegetative phase if all plants in that range are to be in-duced into flower. When a portion of plants are to be in-duced into flower, a separate greenhouse section is neededfor cooling. Providing low temperatures to young plantscan induce variable, premature spiking and slow down veg-etative growth, which are undesirable.

Phase 3: FinishingThe finishing phase describes the period from spike

emergence through spike development and flowering.After cooling, plants may either be transferred to a separatefinishing area for flowering or remain in the same section asthat during the cooling phase. Plant spacing is the same asduring the cooling phase. Temperatures in the range of 63°Fto 79°F (17°C to 26°C) are used during finishing. At thelower end of this temperature range, some hybrids mayhave increased spike and flower bud number and lateralbranching of the inflorescence. It is important to avoid ex-tended exposure to temperatures above 79°F (26°C) duringthis final phase. High temperature can reduce flower budnumber and flower size, and flower buds may abort.

Following spike emergence, the rate of development to-ward flowering is controlled by average daily temperature.For example, in research conducted at Michigan StateUniversity, as constant average daily temperatures increasedfrom 57°F to 76°F (14°C to 26°C), the average time from spikeemergence to flowering decreased from 266 to 52 days (Table1). This time varies somewhat by cultivar, with some flower-ing earlier and some a few weeks later. Based on this infor-mation and grower experience, growers can adjust the tem-

perature to finish a phalaenopsis crop fora particular market date.

An important component of the fin-ishing phase involves staking andpreparing phalaenopsis for sale.Properly staking the inflorescence willaffect how the plant is presented at pointof sale, thus improving consumer ap-peal. In addition, staking will also mini-mize plant damage during packagingand shipping. Plants can be staked whenthe lowest flower bud on an inflores-cence has reached the size of a marble.The stick (bamboo or other materials)used for staking should not be tallerthan the lowest flower bud and can beattached to the inflorescence using clipsor ties. At the time of staking, plants areoften sorted based on a predeterminedquality grading scale (i.e., number ofspikes and flowers or spike length).

PostharvestWhen plants have at least one or two

open flowers they are ready for sale and

P R O D U C T I O NO R C H I D S

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Staking plants is an important step during the finishing phase.Plants can be staked when the lowest flower bud on an inflo-rescence has reached the size of a marble.

Young plants spaced after transplanting into 5-inch (12-cm)pots.

89 October 2005 • Greenhouse Grower

can be packaged for transport. Thepreparation of plants for shipping andmarket display is a labor intensiveprocess that can involve many tasks.Phalaenopsis leaves are sometimescleaned and plants are placed into deco-rative ceramic or terracotta pots withsphagnum moss on the surface of the

growing medium. A label with care information is often af-fixed to the support stick and leaf shinemay be applied to the foliage before theplant is sleeved. Potted phalaenopsis areperceived by consumers as elegantplants with high ornamental value. As aresult, all of these steps can add value tothe product and influence how the plantis presented to the consumer.

Flowers of all orchids, including pha-laenopsis, are very sensitive to low con-

centrations of ethylene, and concentra-tions as low as 0.1 ppm will cause flow-ers and buds to drop within a fewdays. Research at Texas A&MUniversity showed that fumigatingflowering phalaenopsis with 1-methyl-cyclopropene (1-MCP, or EthylBloc) at0.2 ppm for six hours at 77°F (25°C)protects flowers from ethylene concen-trations as high as 10 ppm. However,the duration of protection from 1-MCPis short (seven days at 77°F or 25°C)and the duration of protection declinesas temperature increases.

In conclusion, growers have manyoptions to produce flowering pha-laenopsis orchids. Immature plants willcost less than mature ones, but will re-quire a longer production time and ad-ditional expenses. At northern latitudes,one of the largest production expensesis the energy for heating a greenhouseto promote vegetative growth. Growerswho wish to reduce production timemay choose to purchase more expen-sive plant material that is of floweringsize and can be immediately forced.

A simplified schedule for the pro-duction of phalaenopsis in 5-inch potsis provided in Table 2. From this sched-ule and with the information in ourfour-part series, you can develop a pro-duction schedule to fit your green-house operation and produce a crop offlowering potted phalaenopsis orchids.Although this article has focused on en-vironmental control of growth andflowering, cultural factors such as wa-tering, fertility, pest and disease controland selection of an appropriate medi-um are also highly important for pro-ducing a profitable crop. GG

About the authors: Matthew Blanchard andRoberto “RoLo” Lopez are graduate assis-tants and Erik Runkle is assistant professorand floriculture extension specialist atMichigan State University;runkleer@msu.edu. Yin-Tung Wang is pro-fessor of floriculture at Texas A&MUniversity; yt-wang@tamu.edu. The authorsthank the Fred C. Gloeckner Foundation,Project GREEEN and private greenhousecompanies that support orchid research.

P R O D U C T I O NO R C H I D S

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Correction

In article two of “The OrchidGrower,” August GG, page 70, thecaption for Figure 1 was incorrect.The “coarse sphagnum peat” andthe description for the mix were notin the right places. They shouldhave been swapped.