Since it's my nature to obsess over things, and also look beyond what's widely accepted, I have been researching a little about Opuntia (prickly pear cactus) and their fruits (tunas).  This reminds me that there is always something new that's older than the hills, and always something common that no one knows about.

In the book, "A history of fruit varieties" edited by David Ferree there is a discussion of The 'Reyna' ('Aldajayucan') Cactus pear.  This book was a bonus for me from Raintree, I don't know if it is available electonically. Reyna is a white-fleshed fruit, grown where conditions are dry or drought affected.  It was selected from wild varieties in the 1950s for thin peel, reduced # of seeds, juiciness, and sweetness.  Now, there are about 37,000 acres planted with Reyna in different states in Mexico.  In those areas, the soil is poor and the annual rainfall only 400-700mm.  The plants reach 2.5 meters in height with a canpy 4-5 meters in diameter.  Yield is 10 tons per hectare but can be up to 40 tons per hectare with irrigation and addition of organic matter.  I doubt they would grow here, but are an example of the productivity.  "Fruits are oval flat with green yellow peel and bright green sweet flesh."

Article about Prickly Pear Jam.  High in pectin.  These are a red-flesh variety.

"Opuntia, a Fall Fruit" - There are nearly 300 species.  A few are native to Northern American climates, including East Coast, Midwest, and Northwest.  Opuntia humifusa:  "Bright yellow flowers occur in late spring or early summer.  The pollen is highly desirable to bee populations.  If fertilized, green fruits begin to form, ultimately maturing in late summer, turning reddish green.  The pulp is ruby red and tastes similar to watermelon."

Some diversity of Opuntia fruits - flavors compared to kiwi, peach, persimmon, banana.

Edible Landscaping - "Opuntia tuna" - is that really the correct species name? - tolerant to many bad conditions, but not surprisingly, not to wet soil or shade. 

I grew this one in my front yard.  It grew big enough to bloom, but I don't remember what I did with the fruits.  I have a vague memory that I skinned and ate them, but my memory is often flawed.   It reached about 3 feet tall, but died during a cold wet winter.

It needed 5 years to reach this size, and I had not tried to raise the bed or improve drainage, which may be why it died.  I think this was Opuntia englemani.  It grew a new level of pads each year, which makes it possible to estimate the plant's age.

With a changing climate, it should be worthwhile to pioneer different plant types to see what will survive, thrive, and produce.

In Chile, about 9000 tons of opuntia fruit are produced annually.  Some nice photos on that blog link.  "Once the thick and potentially spiny skin is removed, the fruit is refreshing, juicy, sweet and a little acid, with a taste slightly reminiscent of a honeydew melon."  Some people burn off the spines on a grill or with a propane torch.

Apparently, cacti were domesticated over 8,000 years ago.  That would make them a truly ancient food.   Opuntia fruits were in the diet of the Aztecs.  More information about Opuntia fruits / tunas here.  That last article claims 12,000 year historical record.

I can't personally vouch for Opuntia, how well they grow, produce, or the quality of their fruits.  I recently bought a cactus sections to root and start new plants.  I'm aiming for some diversity, between larger varieties, that seem more productive, and some of the wet / cold tolerant ones that seem much smaller.  For starters, I have one from Raintree nursery that claims to have flavorful fruits.  I also bought some pads via Amazon of a Texas varietiy - possibly O. Englemanii, and have a couple more, from Northern North America sources, from a Colorado collector that claims cold hardiness.  They all have such beautiful flowers, and deer wont eat them, so they have a place as ornamentals.  I have a semi-burgundy colored hybrid, Baby Rita, but no claims are made about the fruit. This is all an experiment, since few people are interested in cactus fruits and there has been minimal development as far as garden friendly varieties, cold hardy varieties, that produce worthwhile fruit.

In my area the Hispanics eat them all the time and mix them with all kinds of food raw. Eggs, Beans etc but I never try this fruit.

This winter I bought some opuntia starts.  They were just the pads, no roots.  I read they root easily.  Now they are in cactus soil in a sunroom.  Hopefully they will root and can go outside in the Spring.

They are quite spiney.  Something tells me that deer won't be a problem.  I might be wrong.

John, thanks for the advice.  I'm happy to share mine too, once they start growing.  I looked at the Texas opuntias today, and there are roots coming out of the bottoms of the pots.  If they make it through the winter, they should start growing in 2016.  The "Baby Rita" hybrid could bloom next year, since it's bigger, so maybe some fruit?  With red-ish pads, I wonder if the fruit will be red.

John, Im still that way.  When a cutting grows roots, Im still amazed.  A stick shouldn't grow roots.  But they do.  Even more so for grafting.  What an incredible thing, that you can cut off pieces from one plant, attach them to another, and they grow as if they were always one plant.  It doesnt feel possible!  I take photos of my grafts and look at them over and over again.