(What do “Grow Cool to Hot” and “Full Sun to Deep Shade” mean?)
If you are like me, we seek out a lot of our orchid culture information online at orchid forums, discussion lists, and websites (I always go to Jay Pfahl’s Internet Orchid Species Photo Encyclopedia (IOSPE) website first). In those online references, you’ll often see very broad ranges of cultural conditions mentioned, sort-of like my subtitle above. So what is that telling you?
Many interpret that type of cultural guidance to mean the plant can handle pretty much anything. However, there are more things to be considered when interpreting that information.
Knowing that orchids are very highly evolved, and that each has its own “niche”, we should consider that it may mean that the populations in nature may come from a wide variety of different conditions, not that an individual plant will tolerate all of the above. You may have one that grows hot, while another might prefer cold, depending upon its source.
Good references will tell you geographically where the plant originates, and at what altitude it can typically be found. The “where” part can give you some idea of the typical temperatures and humidity levels, as well as possible seasonality, but the “altitude” part may lend information about changing the conditions and adding day-night variations to the mix.
Let’s start with seasonality. Species native to equatorial regions may be exposed to pretty much the same temperatures and humidity levels all year. Both will tend to be higher than those seen in more temperate regions, but local conditions can still vary. A plant growing farther from the equator, on the other hand, will see seasonal variation (and likely lower levels) of both, and changes in light levels as well. We are aware that light intensity decreases as one moves from summer to winter, but plants growing in deciduous forests may actually see an increase in light in the winter.
Then there is diurnal range – that phalaenopsis species growing close to sea level near the equator will likely see similar daily highs and lows year round. whereas a Mexican laelia growing at high elevation might see highs in the 80°s and lows in the upper 30°s! The Baker’s orchidculture.com website is a fantastic place to get such information on species.
OK, so how do we deal with such information?
First, learn before you buy! Don’t acquire a plant that simply cannot tolerate your conditions. However, if you simply have got to have it, start somewhere in the middle, growing the plant in intermediate temperatures and partial shade for several weeks to a couple of months, and observe. Are the leaves getting darker? Consider increasing the light levels. If not, but is the new growth is elongating, getting “leggy”? It’s probably too warm.
Keep heat dissipation in mind, as well. A plant grown brighter will absorb more solar energy, and will turn more of it into heat, so it may need to be grown cooler to compensate.
With patience, experimentation, and good powers of observation, you will likely find the “right” conditions for such wide-ranging plants, and can probably “push your limits” as you gain experience.