Our Most Widespread and Adaptable Plants

When we think of hardy plant life that can be found almost anywhere, we tend to think of things like grasses, willows, junipers, and even some of our native oaks which can be found everywhere from swamps to bone dry parts of the Arizona mountains.  While these plants do tend to be widespread, they are also quite specific in their needs and do not thrive or even survive in habitats that they are unaccustomed to.  Granted, things like the short grasses of the high plains and the various oaks got the way they are through adaptation, but it was less of an evolution and more of a taking advantage of conditions that other plants could simply not compete with them over.  They are indeed survivors, and without them, North America would have a lot more desert-like wasteland about.  

But what about those deserts, where only the strongest plants, animals, and even people seem to make life happen?  They are hardly as barren as they seem, especially in the higher reaches where just a little bit more rain falls to make the difference between true aridity and a thriving community of nature that takes what it can get from slim pickings in resources of water.  The shrubs and other plants there either look far down into the earth for water (most mesquites have taproots that extend 60 feet or more into the ground) or have widespread roots that suck up as much of the wet stuff as they can when rain does finally come.  Again, though, these are plants that have become accustomed to certain conditions.  One would be hard pressed to find some of these plants in the tropical parts of Mexico or in the frosty boreal forest.  

There is one family of plants that does just this, however.  They are the cacti, and they are pretty ubiquitous plants:

Yes, I forgot to fill in the Caribbean islands, and they grow there too.  Let's keep this to the mainland I suppose.

North America, more than any other continent of the world, is a dry place.  Sure, we have small areas such as the Pacific Northwest that are usually drenched, but even there, drought is never guaranteed to stay away.  Some of our most severe drought to date can be found in the normally humid and rainy Georgia and Alabama.  Despite having a reputation as a gloomy city, Seattle actually gets as much rain as New York City in an average year of precipitation, and some fine days may boast sunsets unencumbered by even a single cloud in the sky.  On top of this, we also tend to get extremes in temperature that, while not considered normal occurrences, do not exactly come as a shock either.  Again, we have plants that can take all sorts of conditions, but are usually only found in some parts of the continent, such as the prairie flowers which are becoming very popular in gardens as water bills continue to rise.  Cacti, on the other hand, can be found in habitats ranging from the boreal forest to the tropical parts of Mexico.  They can be found near the treeline in the Sierra Nevadas, or growing between the rocks at the edge of the salt flats in Death Valley.  All but one species, in fact, are native to the Americas, with the highest diversity being concentrated in northern and central Mexico (which is also the center of diversity for pines).

They are true survivors and have evolved in a remarkably short period of time.  No fossils of cacti have ever been found, but their restricted natural distribution to the New World suggests that they developed from other plants sometime after the Americas became isolated from the rest of the world landmasses, which means they could have developed anytime during the past 130 million years.  In comparison, pines (another very widespread and adaptable type of plant) have been with us possibly as much as 290 million years ago, and trees in general are thought to have developed into recognizable forms (if not species) as early as 100 million years before that.  Cacti started out with leaves, but diverged from other plants by growing spines that would soon replace the leaves, the function of which would be taken over by the very skin of the plant itself. The only remaining survivor of this original form is known today as the Rose Cacti (Pereskia Grandiflora):

The stem of the Rose Cactus, courtesy of R.A. Howard @ USDA-NRCS PLANTS Database

The Rose Cactus is native to northeastern Brazil, which is actually a fairly wet place.  Some drier parts of the region exist, but for the most part the sky dumps about 40-70 inches of rain a year on the ground.  At the same time, the soil is not the best that Brazil has to offer, being a sandy affair that often drains and dries quite quickly.  (I was looking for reasons to go to out of the way parts of Brazil one day, and seeing one of these in habitat for myself might just do the trick.  Brazil also happens to be the world center for genetic diversity in palms!)  What sort of a plant would thrive in conditions where water was available, but not necessarily all of the time?  This sort of plant, with a stem that turned from something that still resembles wood into something that could also store quite a bit of water.  As part of its transition from a woody plant into something a bit more succulent and softer, it grew spines to protect and also shade itself.  It retains its leaves for photosynthesis, as its skin is still largely a woody business, and apparently has dazzling flowers.  What happened to its off-shoots then?  They kept the spines, ditched the leaves in favor of a nice green (but not always) body, and definitely kept the flowers.  

Arizona Barrel Cactus (Ferocactus Wislizeni), taken during a very memorable misty day in Saguaro National Park, Arizona.  

Cacti flowers, in fact, can be among the most brilliant and noticeable blooms of any wildflowers.  My favorite that I have thus encountered (and lost the pictures for, sadly) would have to be the Beavertail Cactus (Opuntia Basilaris).

Brother Alfred Brousseau @ USDA-NRCS PLANTS Database

They add real vitality to a desert scene when most of the spring wildflowers have already started to succumb to the higher temperatures and onset of summer dryness.  Cacti definitely do tend to complete a desert scene, and a popular conception of the American southwest often has a butte framed by a sunset with a Saguaro (like the one in the background of our blog) raising its arms to the sky.  They tend to stand out even more, however, in places where they are least expected, such as in a sandy patch of ground in a forest in Michigan, a beach on Long Island with a backdrop of New York City contrasting with it, or even growing in mossy cracks in the granite of the Canadian Shield in northern Ontario!  I can tell you from personal experience that they look very, very exotic in these settings, but not entirely out of place either, sort of like finding a Royal Palm in the Everglades or a lone towering pine at the edge of its range growing into the prairies.

That's right, we have a kind of plant that you really can find just about anywhere, one that ties our continent together in a botanical celebration of taking advantage of the weird water conditions our great land throws at us.  This tough little fellow is the Fragile Prickly Pear (Opuntia Fragilis), and it keeps getting found in places where most other plants beyond moss or lichens would just plain give up.  

Taken by Daiv Freeman in Minnesota, copyright 2010.  Daiv has a wonderful website on all things cacti, which can be found at cactiguide.com.  

It has been found (and I highly recommend checking out this article) in Michigan's upper peninsula:

http://opuntiads.com/zpdf/opuntia-fragilis-michigan.pdf

Fragiles have also been found in Manitoba and right across the border around Lake of the Woods in Ontario, and appear quite happy to grow in the otherwise botanically restrictive Canadian Shield rock.  Recent finds have occurred in Kaladar, Ontario and surrounding areas.  They like granite.  They like well-drained soils (like sand).  One figures they might be a bit more common than we think.  Apparently they were one of the first plants to chase the melting glaciers at the end of the last ice age!  Cacti are nothing of short of amazing, and a wonderful part of our natural heritage throughout the continent.  On top of this, they taste great, and look amazing in a garden.  Our native people certainly thought so.