Stanhopea Temperature Requirements

Stanhopea grow well in Tropical and Subtropical climates and many orchid enthusiasts would place them in temperature classifications of intermediate to warm growing.  There are some exceptions and several species tolerate intermediate to cool conditions as well.  Those species that are tolerant of cooler conditions are better suited for growing outside here in southern California due to our cool nights during the winter.  However, most Stanhopea benefit from growing outdoors during the summer and many species are more floriferous when grown outdoors.

There are several temperature classifications for orchids that could apply to the three classes I have described above, however for the uses of growing Stanhopea, I have modified some of these classifications.  The warm classification is primarily 60.0-65.0°F (15.5-18.3°C) average temperatures during winter nights, the intermediate classification is 50.0-60.0°F (10.0-15.5°C) average temperatures during winter nights, and the cool classification is 40.0-50.0°F (4.4-10.0°C) average  temperatures during winter nights.  These classifications are only a general guide for these orchids and some species grow quite comfortably in more than one classification.  Some species such as S. oculata can be found growing well in all three classifications.  This temperature tolerance may be due to the broad distribution of this species and the ability of it to adapt to a wide range of temperature regimes.  Stanhopea oculata successfully grows outdoors in the U.S.in such differing climates as Hawaii, Florida, southern California, and Puerto Rico.  For a complete list of recognized species and temperature requirements see the Stanhopea Temperature Requirements Table 

Here in San Diego my Stanhopeas have been subjected to temperatures as low as 31.0°F (-0.6°C) and as high as 105.0°F (40.6°C).  I expected some damage to the leaves of the Stanhopea plants with the lowest temperature just below freezing, but no long term damage was evident.  Even a few weeks after the light freeze, there did not appear to be any damage to the plants.  One factor that could have assisted the orchids is that I grow many of them under the canopy of trees, and these canopies may have protected them from frost.  The warmest temperatures of 105.0°F (40.6°C) are often accompanied by low humidity and drying winds, so I usually mist or even water the plants daily for the few days in the year when there is excess heat.  Just to clarify, the extreme temperatures listed above were only for brief periods of time, and Stanhopea cannot tolerate extremes in heat or cold for extended periods of time.

The average temperatures in my growing area for winter are 46.0°F (7.8°C) at night and 65.0°F (18.3°C) during the day.  The average summer temperatures in my growing area are a bit higher than San Diego's listed temperatures due to the fact that I live a few miles inland from the ocean.   The average summer temperatures are 65.0°F (18.3°C) at night and 84.5°F (29.2°C) during the day in my  growing area.  These relatively mild conditions are appropriate for growing several of the intermediate to cool tolerant species such as S. oculata, S. tigrina, and S. wardii.  These three species are what I call the “Big Three” of Stanhopea culture because they are easy to grow and relatively easy to obtain from orchid nurseries in my region.  The warm growing species such as the hornless Stanhopeas, S. annulata, S. cirrhata, and S. pulla and the Candida group (S. candida, S. grandiflora, and S. reichenbachiana) require warm temperatures during the winter [nothing below 60.0°F (15.6°C), if only briefly].  These warmer growing species also seem less tolerant of low humidity conditions and tend to exhibit leaf browning as humidity is reduced.

Stanhopea tigrina var. nigroviolacea 'Predator' on left, Stanhopea tigrina var. nigroviolacea center and left

When choosing a Stanhopea to grow, try to ensure that you can provide the best growing conditions that match the natural growing conditions of the species.  For example S. tigrina grows in the mountains west and north of Veracruz at elevations from 1,969 to 5,577 feet (600-1,700 m).  We can learn a great deal about the temperature requirements of a plant by reviewing the climate of the area that it is native to.  This is not a new concept and other growers have eloquently described this in detail.  I have chosen the city of Jalapa, Mexico to demonstrate this concept.  Jalapa is located at an elevation of 4,682 ft (1,427 m) near the upper range of S. tigrina distribution.  Stanhopeas are not native to the city proper but are native to the region surrounding the city, so this provides us with a general idea of what temperatures S. tigrina is subject to (see Table 1 below).  This table provides us with some key pieces of information for growing S. tigrina. First, winter low temperatures range between 52.2-57.6°F (11.2-14.2°C). Second, the two following months in April and May are the warmest months for average high temperatures for the year, and that there is a 19.8-22.3°F (10.5-12.4°C) difference between night and day temperatures known as the diurnal temperature change during the winter months prior to this.  This shift in temperatures appears to have an impact on some Stanhopea species’ ability to increase flower production.  Several growers have had difficulty in blooming Stanhopea species in a more controlled environment (e.g., a greenhouse), but after moving the plants outdoors in spring and summer the plants bloomed more regularly and with more inflorescences. For more information on S. tigrina habitats see Edouard Faria’s blog Stanhopea Passion - Stanhopea tigrina.

Tabel 1. Temperature data for Jalapa, Mexico
Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year Avg.
Average high °F	71.4	73.0	79.9	80.4	82.9	78.4	77.4	78.3	78.3	77.0	74.7	72.7	77.0
Average high° C	21.9	22.8	26.6	26.9	28.3	25.8	25.2	25.7	25.7	25.0	23.7	22.6	25.0
Average low °F	52.5	52.2	57.6	59.9	63.1	61.0	60.6	61.2	61.5	59.4	57.2	54.0	58.3
Average low °C	11.4	11.2	14.2	15.5	17.3	16.1	15.9	16.2	16.4	15.2	14.0	12.2	14.6

Data collected from WorldClimates.com

I grow all of my intermediate to cool growing Stanhopea outdoors throughout the year.  The success I have growing and blooming these species is in large part due to the temperature range of the region I live in, and similarities to the temperatures that species such as S. tigrina experience in nature (see Tables 1 & 2). For example, in my area of San Diego our average winter low temperatures are a little lower than Jalapa at 48.9-52.8°F (9.4-11.6°C), but within the range of temperature variation within the distribution of S. tigrina.  These average winter low temperatures appear to be comfortable for this species and they often continue to grow through January in my area.  This species also performs very well growing outdoors in Santa Barbara, California where the average winter low temperatures are colder 40.3-45.2°F (4.6-7.3°C) (see Table 3).  The winter temperatures in Santa Barbara are cooler than the temperatures in Jalapa, but this adjustment to lower temperatures probably represents temperature tolerance and variability in the species. 

Table 2. Temperature data for San Diego, California
Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year Avg.
Average high °F	65.9	66.5	66.3	68.4	69.1	71.6	76.2	77.8	77.1	74.6	69.9	66.1	70.8
Average high °C	18.8	19.2	19.1	20.2	20.6	21.9	24.5	25.4	25.1	23.6	21.1	18.9	21.6
Average low °F	48.9	50.7	52.8	55.6	59.1	61.9	65.7	67.3	65.6	60.9	53.9	48.8	57.6
Average low °C	9.4	10.4	11.6	13.1	15.1	16.6	18.7	19.6	18.7	16.1	12.2	9.3	14.2

Data collected from climate-zone.com

Table 3. Temperature data for Santa Barbara, California
Month	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year Avg.
Average high °F	63.7	64.6	65.3	67.4	68.6	71.2	73.9	75.4	75.2	73.1	68.5	64.4	69.3
Average high °C	17.6	18.1	18.5	19.7	20.3	21.7	23.3	24.1	24.0	22.8	20.3	18.0	20.7
Average low °F	40.3	43.2	45.2	47.1	50.1	53.6	56.9	58.2	56.5	51.5	44.7	40.1	49.0
Average low °C	4.6	6.2	7.3	8.4	10.1	12.0	13.8	14.6	13.6	10.8	7.1	4.5	9.4

Data collected from climate-zone.com

The month of April is the first month of inflorescence initiation of S. tigrina in my collection and this coincides with a 13.5-17.0°F (7.5-9.4°C) diurnal temperature change in the winter months prior to initiation.  While these diurnal temperature changes are not as dramatic as those in Jalapa, these appear to be enough to encourage the S. trigrina to be consistent in flower production each year and more floriferous.  This is not to suggest that Stanhopeas cannot be grown in greenhouses and bloom successfully.  Several growers have successfully grown and flowered Stanhopeas in warm conditions.  However, it has been my experience that many Stanhopea including S. tigrina grow better, and are more floriferous growing outside here in southern California  rather than in a greenhouse.  I know of several growers who had difficulties blooming S. tigrina until they moved the plants outdoors.  Barney Greer in his book The Astonishing Stanhopeas provides several examples of species (e.g., S. florida, S. maculosa,  and S. platyceras) that he could not bloom in his greenhouse, but when moved outdoors they began to flower.  Other species of Stanhopea that he grew outdoors as a matter of preference (e.g., S. deltoidea, S. martiana, S. ospinae, S. pozoi, S. tigrina, and S. wardii) and others that grow best in a greenhouse with cool [50.0°F (10.0°C)] night conditions (e.g., S. embreei, S. guttulata, S. hernandezii, S. insignis, S. panamensis, S. posadae, S. ruckeri, S. stevensonii).

If you are having difficulties in blooming some of these Stanhopea you may want to try growing them outdoors if you have the proper climate, or move them outdoors for the summer.  Outdoor diurnal temperature changes between [15.0-20.0°F (8.3-11.1°C)] should provide the proper conditions to initiate flowering.  If you don’t have the option of growing Stanhopeas outdoors, try lowering the temperature of the greenhouse during the night in winter and summer a few degrees, down to 55.0°F (12.7°C) or even 50.0°F (10.0°C), if your other plants can tolerate that treatment, you should have an increased chance in flowering your Stanhopea.  Linda Kraus in her article in the American Orchid Society Bulletin “The Culture of Stanhopeas – Confession of a Requited Love” stresses that she grew her Stanhopeas cool with night temperatures of 52.0°F (11.1°C) even in the summer.  Thus she kept her Stanhopeas in a cool greenhouse condition and they bloomed well.

Printed References:
Greer, B. 1998.  The Astonishing Stanhopeas The Upside-down Orchids. Self Published.

Kraus, L. 1984. The culture of Stanhopeas – “Confessions of a Requited Lover”. AOS Bulletin 53(4): 358-366.

Stanhopea costaricensis

Stanhopea costaricensis inflorescence

Stanhopea costaricensis is native to Costa Rica, Nicaragua, and Panama from elevations 1,640 to 3,280 feet (500 to 1000 m).  It is native to tropical and warm forests, and grows best in intermediate to warm conditions. This species does not tolerate low humidity and high light situations and the leaves can burn easily in direct sun.  The inflorescence is up to 8 inches (20.3 cm) long and often 3-5 flowered, making this a good choice for large basket culture.  The flowers are 5.5 inches (14 cm) wide and resemble those of S. oculata.  However, the hypochile has a restricted center portion that makes it form two broad segments that are almost unique in Stanhopea (S. gibbosa has a similar shaped hypochile).

Stanhopea costaricensis flowers

This is a seedling that I purchased from Tropical Orchid Farm of Hawaii and it has a light yellow to cream color in the sepals and petals with several torus shaped (like the letter O) spots that are reddish brown.  The petals have two solid distinct eyes in the same color.  The hypochile is light pink to flesh colored and has dark red eyes and is stippled with red to dark pink small spots.  The mesochile is cream colored and the horns are the same color with the interior portion exhibiting several pink spots.  The epichile is also cream colored with dark pink spots.  This form is an example of variation seen in the species with some forms having less pink and more yellow in the hypochile.  Seedlings can pay off sometimes providing some of the most favorable color variations and spot characters.

Stanhopea costaricensis flower close-up

 

The fragrance of this orchid is camphor scented when it first opens and later it is a combination of camphor and cinnamon.  This species has become one of my new best favorites and a nice fall bloomer that extends the blooming season for my Stanhopea collection!

Stanhopea candida

Stanhopea candida

Stanhopea candida inflorescence

This orchid is native to warm forests and foothills of Brazil, Colombia, Ecuador, Peru, and Venezuela.   It is found at elevations from 330 to 1,970 feet (100 to 600 m).  This is one of the several Stanhopeas that need warm temperatures all year around, so I bring the plant inside the house from November through March.  I grow it outside in the spring and summer months on the north side of the house where it receives indirect light and mostly shade.  This orchid enjoys a warm and humid atmosphere with a relatively moist growing medium.  It also grows well in ventilated ares with a good breeze.  The fragrance of S. candida is primarily the scent of wintergreen.  Wintergreen is one of the major components in the pain reliever Bengay, so that is exactly what this flower smells like, though it is rather light in scent.  This is a fall blooming species of Stanhopea, though some have reported that it also blooms in the spring.

 

Stanhopea candida hypochile with
small pink spots

This Stanhopea is closely related to S. grandiflora and S. reichenbachiana.  The flowers are small (2.75 to 3.15 inches – 7.0 to 8.0 cm) wide, primarily white, and have no real horns.  There are two short curved projections on either side of the upper hypochile.  The remaining hypochile is joined into a short tube that opens to both the upper hypochile and epichile.  On the front side of the hypochile are small pink spots, the only other color on this flower.  The epichile is a short lanceolate shaped projection.  The column is an off white color that is infused with green and is almost florescent. The leaves of S. candida are usually 9.8 to 19.6 inches (25 to 50 cm) long; however, my form has shorter leaves 9 to 12 inches (22.8 to 30.5 cm) long and 2.5 to 4.2 inches (6.4 to 10.7 cm) wide.  These orchids are  rather short  with small pseudobulbs 0.75 to 1.2 inches (1.9 to 3.0 cm) wide at maturity.  The plant may be smaller in size because it is still a little young.  I also grow it outdoors in the summer where it is less humid and warm in comparison to the tropical conditions the orchid finds acceptable.



Stanhopea candida hypochile and column

In side profile the hypochile has a rather rectangular configuration.  The buds of this species emerge through the inflorescence bracts rather early in development, and spend a large amount of time developing outside the bracts.  This is in contrast to many other Stanhopea that allow the buds to develop for a long time inside the inflorescence bracts before they emerge.





Coryhopea Red Martian

 

Coryhopea Red Martian inflorescence with three flowers

 

This orchid is an intergeneric cross between Stanhopea martiana and Coryanthes macrantha var. aureum.  There is a lot of hybrid vigor to the plant and it grows large rather quickly.  The flowers don’t open fully and are best viewed from below. They are quite spectacular to look at and have been described as alien looking.  The fragrance of the flowers is rather similar to cherry cough syrup or cherry cola.  This is a very agreeable fragrance indeed. There are two leaves per pseudobulb. The leaves are lanceolate in shape 18 to 19 inches (45.7 to 48.3 cm) long, and 3.0 to 4.25 inches (7.6 to 10.8 cm) wide.

 



Coryhopea Red Martian flower
photographed from below

The flowers are 3.5 to 4.5 inches (8.9- 11.4 cm) wide and a deep red color with many mahogany to red spots on the sepals, petals, and hypochile.  The sepals and petals are cream to white at the tips with red spots.  The upper hypochile is orange-red to deep red in color and the mesochile and horns are yellow with mahogany spots/streaks.  The epichile is bright yellow on the lower portion with deep red spots/streaks, turning solid red on the upper portion..



Coryhopea Red Martian with
human heart shaped buds

Unopened buds are a joy to watch grow and develop.  Once they mature they almost appear to be oddly shaped human hearts.  This makes the opening of the flowers full of anticipation and almost unnerving! I grow this orchid warm and bring it indoors during the winter given that one of the parents of the cross is a warm growing Coryanthes.  It spends the rest of the year growing outdoors on the north side of my house.

 

 

Stanhopea panamensis

 

Stanhopea panamensis with five flowers on this inflorescence

 

This is a tropical growing species that thrives in warm and humid environments in tropical forests of Panama at 2,950 feet (900 m) in elevation.  This species grows in shade and dappled shade and appreciates being grown outdoors during the summer.  Unfortunately, this is one of the Stanhopeas that I have to take indoors during the winter months.  Some sources say it dislikes temperatures below 60F (14C) at night, others say temperatures near 50F (10C) are fine. Barney Greer's book mentions that a grower did well with this in Sydney, Australia growing outdoors, so there is hope that I could try this one outside when it matures a little more.

Stanhopea panamensis close up of flower

The flowers are large to 5-5.5 inches (12.7 - 14.0 cm) wide and are primarily white with dark purple spots on the petals and sepals. The hypochile is a bright yellow with the remainder of the prominent mesochile and epichile being white. There are small dark purple spots on the upper portion of the epichile and interior portion of the horns of this Stanhopea. This species was once combined into S. oculata, which it resembles. However, S. panamensis doesn’t have eye spots, has a more verticle hypochile, and a different fragrance. The flowers have a faint lily scent at first, almost like an Easter Lily (Lilium longiflorum) or Moon Flower (Ipomoea alba). Later as the flower matures it has a mixture of lily and clove fragrance, but faint. 



Stanhopea panamensis inflorescence 
in bud

The buds of this species have very prominent, dense, dark brown to black scales on the sepals, ovary, and inflorescence bracts. This species is a large plant with large leaves 13-24 inches (33-61 cm) long, and leaf blades 4.25-6.0 inches (10.8-15.2 cm) wide. I have this plant growing on the north side of the house under the eaves in spring/summer. I provide it with 50% shade cloth, and about 2 hours of full morning sun per day in the summer.