Cacti of Minnesota

Most people are surprised to hear that Minnesota is home to cactus. Even more so when they learn not just one, but three species. Living only a 40 minute drive from some habitat chalked full of them, I didn’t learn about their existence until well into college. They have never been common, restricted to dry sandy prairies and harsh rock outcroppings of granite and gneiss. In recent decades a combination of fire suppression, plowing, and mining have drastically reduced their range. Cacti, or at least these species, are by no means a fire tolerant species. Luckily where they grow historically had very little fuel, so fires would rarely reach them or be of rather low intensity. Surrounding habitats with deeper soil produced more fuel and burned more often. Without these areas burning, shrubs like sumac and red cedar get a foothold and start to encroach, even spreading to these drier areas. Even worse than those two natives is the invasive buckthorn which is all over these habitats. Needless to say the future of cacti in MN is not looking too bright. Of the three, only the fragile prickly pear is not a state listed rare species. The granite outcroppings have been massively reduced from their former glory. The lichen species Psora icterica which used to grow here has been extirpated, will the cactus follow?

The best spot to look for them is on rock outcroppings of the Minnesota river. Today’s exploration around Granite Falls yielded the two species of prickly pear. Plains prickly pear is by far the less common. Sometimes they can look similar, especially young plains prickly pear. But plains have much larger, flatter pads. Brittle has much smaller, rounder pads which break off much easier. Both of them do flower, but rooting of broken off pads is how they typical propagate. This is especially true for the brittle prickly pear.   

Overlooking the Minnesota River 

Typical rock outcropping habitat

Cactus from afar

Piles of cut brush needing to be burned

Plains prickly pear (Opuntia macrorhiza)

State Special Concern Species 

Brittle prickly pear (Opuntia fragilis)

To find the rarest species, the ball cactus, you need to go to Ortonville. Here’s a picture from this past winter. 

Ball cactus (Coryphantha/Escobaria vivipara)

State Endangered Species

Later tonight some massive storms blew through western Minnesota, including a few tornados in Danvers and Canby. Maybe the strong winds knocked a few pads loose to start some new plants.