Worsleya cold tolerance

Lee Poulsen wpoulsen@pacbell.net
Mon, 08 Dec 2014 13:41:48 PST
A few of years ago I was traveling to Brazil on business for a couple of weeks every other month for a year. So, now that I've visited some of the areas in the Mata Atlântica, the highland Atlantic coastal forests of Brazil (specifically São Paulo, Mogi das Cruzes, São José dos Campos, Campos do Jordão, Itatiaia National Park, Petrópolis, Teresópolis, Organ Mountains National Park), I have a better feel for what's going on there climate-wise. It's not like any climate I'm used to in the U.S. This area starts a little south of the Tropic of Capricorn and goes for hundreds of miles north along the southeast coast of Brazil with a width of a about 100-200 miles. The region between São Paulo and Rio de Janeiro is smack dab in the middle of it. This area of Brazil consists of a highland plateau of around 2000-2500 feet (600-800 m) above sea level (with various higher peaks scattered all around it). It *rapidly* drops down to the coast with a sea level coastal strip that is at most about a mile (~2 km) wide between the beach and and where the plateau begins. (Except for Rio where there is a bay and the entire city is down near sea level except for the favelas (slums) that go up many of the hills and mounts that stick up all over the city and surrounding areas.)

Since this region is on the east coast of a continent, it has the typical humid climate associated with that, especially during the summer. However, due to the higher elevation than what is typical of the populated areas of the eastern coasts of North America, Asia, and Australia, the temperatures never get as hot in the summertime. And it cools off more during summer nights than it does in the Northern Hemisphere. I also think that the cooler ocean temperatures at similar latitudes in the Southern Hemisphere also contribute to cooler night-time temperatures in the summer than what is experienced at similar latitudes in the Northern Hemisphere.

In any case, it experiences cooler night-time temperatures during the winter than I would have thought, and cooler daytime temperatures in the summer than I ever would have imagined. It is very humid, and rains an incredible amount in the summer. But is otherwise more comfortable than I would have expected in the Tropics. Mauro Peixoto, who offers seeds of hundreds of Brazilian natives, has measured temperatures at his farm (at about 2500 ft a.s.l.) in Mogi das Cruzes for several decades. He told me that it used to drop down to 0°C once or twice every winter until about 20 years ago. Now it only gets down to +4° or +5°C on the coldest nights. The lowest temperature he has measured at his place is -4°C. Quite a few plants from much further north closer to the equator froze. But none of the mature plants from the Mata Atlântica had any problems at all. In the summer he almost never sees any temperatures above 30°C (86°F) because a fog always comes up the cliffs from the coast every afternoon just as it starts to get a bit warm. This also occurs in the Organ Mountains which are much further from the coast than Mauro is. It's pretty interesting to experience. For those of you who grow fruits, just to show you how unusual a climate it is, I saw with my own two eyes on Mauro's property, persimmon trees with fruit on them growing right next to pineapples with fruit. I think persimmons need at least 200 chilling hours each winter to produce fruits, while I thought pineapples couldn't stand any cold weather, but Mauro says they both fruit every year without any protection or assistance. Also, all the orchids in his shadehouse that are native to the forests in his area have never been hurt by even the -4° night they experienced.

My mature Worsleya has never had any problems with temperatures down to 0°C, or maybe a degree colder than that. (I don't leave my seedlings outside in the winter--they're too valuable to possibly lose.) But remember, it always warms up above freezing during the day in So. Calif. even on the coldest days, and the same is true in this area of Brazil.

In any case, if you want to kind of see what Worsleyas experience in their native habitat, I finally found actual weather data for the Organ Mountains National Park which is their home (after searching for it for the past 15 years). I plotted the temperature and rainfall data and have uploaded it to the wiki:


--Lee Poulsen
Pasadena, California, USA - USDA Zone 10a
Latitude 34°N, Altitude 1150 ft/350 m

On Dec 7, 2014, at 11:52 AM, Jim McKenney <jamesamckenney@verizon.net> wrote:

> Over the years we've had several discussions which touch on the cold tolerance of Worsleya. From those discussions and from reading elsewhere, I came to the conclusion that it would be safe to leave my Worsleya out during light overnight freezes.
> Earlier this year  I was given a huge Christmas cactus (a member of the Schlumbergera Buckleyi Group). It's now loaded with buds and blooms. When I moved it inside in anticipation of the first overnight freeze, a branch or two broke off. I forgot to bring those branches in, and the following morning found them, frozen hard. Keep in mind that the temperature was below freezing for only about two hours.After a while inside they defrosted and showed no cold damage. They kept their flower buds and are now developing normally. 
> In reading the wikipedia entry for Schlumbergera,  I found this passage which is worth quoting for those who might have doubts about the tolerance of these "tropical" plants for brief sub-freezing temperatures:"Because of their height and proximity to the Atlantic Ocean, the coastal mountains produce high altitude moist forests – warm moist air is forced upwards into higher, colder locations where it condenses. Schlumbergera species grow in habitats which are generally relatively cool, shaded and of high humidity. David Hunt describes collecting specimens in conditions of cloud, drizzle and overnight temperatures down to −4 °C (25 °F)."
> This is in the same part of Brazil where Worsleya grows. 

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