Dixie Dringman

For many years I avoided controversial issues because I knew people were not easily swayed from their beliefs, even when the proof lay before them. Then I became involved in one of the most controversial and heated issues ever: The study of cacti.

A strange part of human nature is to create organization from chaos. Even with cacti. I began asking why there were hybrids scattered over Canada and the Pacific Northwest with no sign of their parent species. Why do we see Opuntia erinacea var. columbiana and what happened to its family ties? Even the Pediocactus nigrispinus, which has obviously evolved from Pediocactus simpsonii, its widely scattered cousin, raises the question. Why should these cacti become separate species? Why not variants?

In this article, I express my views of a debatable subject. I do believe that my hours in the field studying these cacti qualify me to give an opinion. Not everyone will agree but, on a topic that currently has no proof, no one should make their stand in concrete.

Three cacti live in Washington. Two are endemic to Washington State. My studies have led me to believe that the odds of the cacti existing in any number, if at all, before 15,000 years ago is quite unlikely. The geological information below brings me to this conclusion.

One hundred fifty million years ago Spokane was the west coast of Washington State. Part of what was to become the rest Washington floated in the Pacific Ocean, a tropical island on a collision course with the main continent. This island and other scraps of old Pangea combined to make Washington. Fifteen to seventeen million years ago a meteor impacted in Southwestern Idaho. This impact directly or indirectly generated enough basalt in a couple of million years to cover most of Eastern Washington. Some of these basalt flows were two miles thick. Eastern Washington now looked like a rocky table top.

Seven million years ago the Cascade Mountain Range was pushing up, dividing the state into East and West. This formed a rain shadow that slowly turned the eastern two thirds of the state into the semiarid place it is today. Two million years ago the Ice Age began: Glaciers covered most of Western Washington including the San Juan Islands and Canada. In Eastern Washington the Okanogan and Republic areas were under a mile of ice. Ice crept as far south as Chelan. There were, of course, times when the ice retreated to the north for extended periods. During this period the weather was dryer than it had been in the past since a majority of the water was entrapped by the glaciers. Most likely it was during this transition from a warm, humid climate to cool, dry climate that cacti evolved.

Fifteen thousand years ago the Ice Age and its massive glaciers began their final retreat. This set the stage for the greatest geological event to strike Washington State: the Bretz Floods. The floods would begin as a glacial lake (on an average of about 500 cubic miles of water) originating in Montana. As glaciers moved across the Clark Fork River they dammed it. When the ice dam could no longer withstand the pressure of the water behind it, it would burst. This would release 9 cubic miles of water per hour. This water would be moving at close to 40 miles per hour, and up to 2.000 feet high. No one knows for sure how often this happened but the general consensus is close to 40 or 50 times. These floods washed across Eastern Washington, eroding everything in their path, depositing sand and gravel 1,000 feet or more above the current river levels, and replacing a lot of basalt with these depositions.

Today, the eastern two thirds of Washington are called the ‘Channeled Scablands’, and these lands provide excellent habitat for a few cacti. Opuntia hybrids range well into British Columbia: Following their habitat has taken me as far north as Spence’s Bridge along the Thompson River. These hybrids are quite distinguishable from others because they are small and delicate. They have spread across the Canadian/U.S. border with a few nice swarms at the border outside of Nighthawk. They grow in scattered groups through the Okanogan and follow the Columbia River as far south as Wenatchee. Interestingly, in the San Juan Islands, Terry Dominico conducted a four-year study on the pure form of Opuntia fragilis there.

Why are the San Juan Island cacti pure? And why, here in Eastern Washington, are they completely hybridized? Terry Dominico’s theory is that Eastern Washington Indians used 0puntia fragilis as a trading commodity with the coastal Indians and the coastal Indians possibly acquired enough 0puntia fragilis to begin cultivating it on their own. Here they avoided contaminating the pure island forms with the hybrids that began to take over. This would have occurred about 10,000 years ago.

I have wondered whether a pure form of 0puntia fragilis came from the mid-plains states quite recently as opposed to the thousands of years that are usually suggested. Indians could have transported them well after the Ice Age receded. This late-arriving 0puntia fragilis might then have very little, if any, connection with our Opuntia hybrids. The locations of 0puntia fragilis is usually connected to Indian encampments, so I speculate the pure 0puntia fragilis now known in Washington (and possibly in Canada) was most likely introduced by natives within the last four to six hundred years.

If this is true, then our hybrids were not derived from ‘local’ Opuntia fragilis but transplanted themselves from another unknown location. Opuntia hybrids have been confused with Opuntia fragilis, Opuntia erinacea or Opuntia polyacantha. It has been considered a strange form of Tephrocactus and a new species of Opuntia. This can all be derived from one colony of cacti, as variability within the group is almost limitless. It is very likely an Opuntia fragilis hybrid of some type.

This has created a situation that, due to our desire for conformity, taxes us. The flowers, spines, and pads are all unhampered by any set rules. Flowers are yellow with an occasional double petal, making them quite reminiscent of roses. The pads are dark green with red- to bone-colored spines. These spines are not as long as the Opuntia erinacea var. columbiana but they are barbed. An occasional tuberous root growth can also be found but has no apparent consistency—it is simply one of many variations in this cactus. Opuntias easily interbreed, so the theory is that, after sexual hybridization, the cacti colonized vast areas asexually. This was an evolutionary device to speed up reproduction in those cool, short summers located at the toe of a glacier. As the hybrids adapted to living in this zone, they followed the retreating glaciers north. These hybrids never reverted to sexual reproduction; even today seeds are very rarely produced even though flowers are prolific.

If there were pure forms of Opuntia surviving in small scattered patches when the glaciers of the last Ice Age receded, they would have to compete with the better-equipped hybrids. These hybrid Opuntias grow in low tight mats that effectively choke out any plants that are in their path. Only a few determined blades of grass and an occasional sagebrush grows beside these hybrids. And if hybrids established themselves close to their pure parents it would only be a matter of time before the offspring choked their parents. And with the hybrids’ ability to survive in wet ground and in running water, they had a direct advantage over pure forms of Opuntia in the wet ground of glacial drainages. Possibly, in other areas the pure Opuntias effectively committed suicide by hybridizing themselves out of existence.

Today Opuntia hybrids are found all along the Columbia River and surrounding hills. Each swarm is different from the one down the road, yet is still the same – which is difficult to fathom unless you see them. Some have graced the sides of golf courses, other have settled under power poles into an acre-large mass. That acre patch is one of the most spectacular masses I’ve seen and in mid-June displays yellow (and the occasional pink) flowers.

To me the conclusion is simple: We only have hybrid Opuntias and not the pure parent forms because the hybrids adapted to the climate. They grew in wet, acidic, areas where most cacti languish and evolved to become the preference of the post Ice Age period.

The other Opuntia indigenous to Washington is Opuntia erinacea var. columbiana. This species is quite different than its relative, the hybrid. Where the hybrids are more adapted to the acidic wetter areas, the Opuntia erinacea var. columbiana prefers the calciferous basalts and their clay based soils.

Opuntia erinacea var. columbiana has light green pads that are plump and ovate in the spring when water is plentiful. Later in the season they shrivel and their prosperous look gives way to a more withered look. Often, due to the long white spines shining in the sun, Opuntia erinacea var. columbiana looks as if it is covered in spider webs. Yellow flowers adorn the cactus in mid-June. Much like its hybrid relative, Opuntia erinacea var. columbiana does not produce seed. It does not have the barbed spines of the hybrid or the fragile joints that dislodge and attach at the slightest touch. Nonetheless, the Opuntia erinacea var. columbiana pads are found scattered along elk and deer trails, a reminder of how well asexual reproduction does work. We’ve heard the term ‘use it or lose it’ many times. I hope this does not apply to the flowers of the non-seed producing Opuntias, as they are quite beautiful even though their reproductive purpose has been removed.

The big questions about Opuntia erinacea var. columbiana center around where and why they originated. Some people believe these are another Opuntia hybrid, a cross between Opuntia polyacantha and Opuntia fragilis. I disagree. Opuntia erinacea var. columbiana is very distinct from the typical Opuntia hybrids, it grows in a different habitat, and the hybrids have a far wider distribution area.

Opuntia erinacea var. columbiana has been confused with Opuntia polyacantha in many books which had led to confusion in the field. Lyman Benson correctly describes them in Cacti of the United States and Canada. I have no doubt that they freely hybridize with other Opuntias that may intrude into their habitat, but in most regions they remain a distinct species. One of the many mysteries surrounding the Opuntias of Washington is how they relocated after the Bretz Floods that scoured Eastern Washington 10,000 years ago. The hybrids along the Columbia River and the Opuntia erinacea var. columbiana in areas such as Dutch Henry Draw and the Yakima River were destroyed when these floods rushed trough. There were periods between floods of 40-70 years, giving the cacti time to repopulate but from where? My guess is that higher areas were not affected by the water and, after the deluge, deer, mountain goats, coyotes and more carried pads down to the draws and rivers as they came looking for water.

Both forms of Opuntia and Pediocactus nigrispinus are exposed to the hazards of fast hot grass fires that race across the land. I have never found severe fire damage on either Opuntias or Pediocactus nigrispinus–the fires cross over cactus so fast that their tough epidermis not affected. The spines are sometimes burned but that does not harm the plant. Meanwhile burned habitat stripped of competing grasses may help the cactus expand its range.

The great lava flows that covered Eastern Washington created a unique habitat that issued in the evolution of Pediocactus nigrispinus. The basalt (lava that has issued from the earth and is exposed) is quite calciferous and on some of the outcroppings the deposits leech out to form a thick layer of white calcium that stands out quite clearly on the dark red rock. The basalts erode very slowly and, on the basalt flats, time seems to have stopped. In this stable environment the slow growing Pediocactus nigrispinus lives, flowers, produces seed and dies. It is very possible that Pediocactus nigrispinus was well established in all of the basalt hills and cliffs long before the Bretz Floods. Generally the Pedios and the glacial paths did not cross, so Pedios were probably not directly affected by the sheets of ice.

The Bretz Floods, on the other hand, did have a great effect on Pediocacti. The walls of rushing water washed away many plants. And where the water slowed and dropped its load of debris, sand and gravel would have been deposited over the basalts, The sand covered hills have the same flora as the Pediocacti habitat but sand is too unstable and does not contain the necessary nutrients to support the Pedios. Now Pediocacti are in scattered groups found at the 1,000- to 4200-foot elevations.

Pediocactus nigrispinus grows at a rate of about half an inch a year. At this rate low habitats with shifting sand would never allow the roots to become established. Higher, thinner basalt layers, however, are an excellent medium for cacti–the main tuberous root of Pediocactus nigrispinus can forge its way into rock cracks. The finer roots near the surface absorb moisture and nutrients in the thin layer of lithosoil.

Climate is another challenge for Pediocactus nigrispinus. These plants grow in the harshest environment of any of the Pediocacti. At the upper level of their range, they survive winter temperatures of -20 F and wind chill indexes below -40 F. Summer dishes out 100-degree days. Rain is sporadic (9 to 12 inches per year) with March, April, May and October producing the most precipitation. Flowers begin opening in April. Most are magenta, but some are pale pink and a few are peach. A month after they flower, the seeds are mature. The pods split and the seed falls to the ground. Most become food for insects and rodents; a few do survive to continue the cycle.

These, then, are the cacti of Washington State, and while all three have been confused with other species, I hope this story clarifies which cacti really do inhabit the state and how special they are. In closing let me again clarify that much of what I have stated is speculation and could be deliciously right or wildly wrong. Today, through DNA testing, we do have the means of proving beyond a doubt where our cacti originated. This will, in the near future, set the family tree of cacti in concrete.

This post was originally published on 4/27/07. 

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