In June 2016 I went on one of my most spectacular botany trips ever. That is saying a lot since I have on some outstanding trips. This was truly one of the best.
Normally I am a bog guy. I love bogs. I love the orchids and other plants that inhabit our wetlands. Most of my flower hunting has been in these wetlands. Today I felt a bit like a faithless lover because I wandered a near desert in search of cacti. I have come to love cacti as much as orchids. Both are pretty close to divine.
I love deserts. I just never thought I would experience one in Manitoba. Actually, I did not experience one that day. It is not really a desert but it is as close as we get in Manitoba. Spruce Woods gets about twice the amount that is the limit for what is considered a desert. The annual moisture received there is 300-500 millimetres per year-nearly twice the amount received in a true desert region. This rainfall enables plants to colonize the sand dunes, hiding most of the sand. In fact as I walked along the trail I was struck by the great variety of vegetation. For a plant guy like me that was fantastic.
Of the original 6,500 square kilometres of delta sand, only four square kilometres remain open today. The balance is now covered with vegetation that is gradually covering the sands. Most of the sands are now covered with a rich variety of plants and wildlife. The Spirit Sands had their origin more than 15,000 years ago when the ancestral Assiniboine River, was much larger than it is today and it created a huge delta as it carried glacial meltwaters into ancient Lake Agassiz.
The origins of the Spruce Woods require one to consider the massive continental ice sheets that covered Manitoba and much of the northern part of North America. About 20,000 years ago, all of Manitoba was covered by an enormous ice sheet that in many places was up to 2 km. deep. There was an awful lot of water locked up in that ice.
When that fantastic ice sheet started to melt, a wide melt stream flowed into the recently created Lake Agassiz. It was the largest lake the world has ever seen! As the water flowed in it dropped silt, sand, and gravel into many parts of Manitoba including a pathway that was centred roughly on what is now the Assinboine River. This created a huge river valley.
The sand deposits thus created were vast and deep. In places they were up to 200 feet deep and covered approximately 6,500 square km. These deposits spread out in a fan shape that reached as far as Portage la Prairie. Winds created heaps of sand that we call dunes. Large dunes were built up in this area. Those dunes are still active today.
When the great continental ice sheets finally melted away, about 12,000 years ago, the Assinboine River was a mighty river, about 1.5 km wide. The modern descendant is a puny shadow of that. The river drained into huge Lake Agassiz just south of present day Brandon Manitoba. As the glacier continued to retreat northwards Lake Agassiz drained south—opposite of today. The massive ice sheets blocked northward flow. This south flow of the river exposed massive sand from the river delta.
To the aboriginal people the Spirit Sands were a spiritual place close to the Great Spirit or Kiche Manitou. The present name—Spirit Sands acknowledges the religious importance of the dunes to indigenous people.
Today Spirit Sands is a fragile sand dune about 4 km2. The rest of what is left is covered with vegetation. The dunes are moved along the prevailing northwesterly winds and like so many dunes, cover anything that stands in their way.
Cactuses or cacti are magnificent. I have spent a few winters now in Arizona looking at cacti and have come to love them nearly as much as orchids, as heretical as that might sound. Our Manitoba cacti are small low plants but the flowers are extraordinary and can hold their heads up high to any Arizona cacti. And they love sandy conditions.
Many people are surprised to learn that cacti can be found in Canada. After all, are cacti not a plant of the southwestern deserts? Yes and no. Certainly they can be found in the southwest of the US and are in fact famous for that. Yet they can survive in the north as well.
There are actually 4 species of cacti native to Canada. These are Escobaria vivipara, Opuntia fragilis, O. polyacanthaand O. humifusa. None of these species are found farther north than their locations in Canada.
There is another species of cactus in Manitoba that I have not seen yet. That is prickly pear and it can be found from BC to Whiteshell Provincial Park in Manitoba. There are as well a few sites in northwestern Ontario. I have seen this cactus in Manitoba but not when it was in bloom. A nature group of which I am a part, Native Orchid Conservation Inc. went to see it but I had to miss that field trip. Sometimes life sucks. Next year for sure!