Besides being edible, the blossoms of the Prickly Pear will greatly benefit your garden by attracting bees, butterflies and hummingbirds. This is beneficial because the bees and butterflies help pollinate the other plants in your area.
Now you can eat the pads of the cactus pretty much year around. But it is the prickly pear fruit which most people are familiar with. You know when they are ripe when deep red to purple. Here in Texas fruit start to show on the plant around July, ripening in August and continue to put off fruit almost all summer and fall. In fact a large cactus can put off hundreds of fruits during their season.
How To Harvest
The Opuntia has what is called "glochines." I call them "Gotcha's." These are small microscopic thorns / hairs that remind me of really small slivers. They grow in clusters on the plant, so when touch one of these clusters, they will all stick in you. You can pull them out with tweezers or I hear that duct tape also works. They do come out pretty easy, but they are a still "Gotcha" painful.
To get these "glochines" off, you can use running water, you can burn them with a propane torch or even a candle. You can also peel the fruit while wearing tough leather gloves, but I like to burn the thorns off first, then I wash them before I peel them. I want to make sure I have gotten all those little glochines off the fruit, not for fear of eating them, but you will get tired of the little "gotchas" they give you while working with them.
Now you pick the fruit with VERY heavy leather gloves or what I use, long kitchen / BBQ tongs. This way you don't come in contact with these little thorns.
To harvest the pads, all you do is grab a pad and they break off pretty easily. You can also use a knife and cut them off from the base or trunk of the cactus. They are pretty easy to harvest. The pads also have the small glochines, but they surround a large long thorn. They wash off using a hose so that helps in the harvest. Once you pick them you can also burn off the thorns and then peel the outside of the pad with a knife or peeler.
How To Eat Opuntia - Prickly Pear
Holding the football shaped fruit, cut the fruit in half long wise. This will expose the red flesh and seeds. You can eat the fruit raw or cooked down. When they are fully ripe they have raspberry / pear / kiwi like flavor. Just be sure to take the seeds out with a spoon. They are very hard and can break your teeth.
NOW…do not throw the seeds away. Remember this is City Foraging, so we use what we gather. As you clean out the seeds let them fall into fine strainer and wash them off. Put these seeds in your food dehydrator and once they are dried, you are able to put them into your grain mill and grind them into flour.
Once you have cleaned your fruit, you can eat them fresh, make jams and jellies, syrups, fruit juice concentrate, even dehydrate the pulp into fruit leather (fruit roll-up) Pretty much anything you can use standard fruit in, you can substitute with Opuntia's prickly pear.
As for the pads, once you have them cleaned and peeled there are several ways you can eat them. Brush on some olive oil, salt, pepper, garlic and then grill them. When they turn a sage green in color or become pretty floppy, they are finished. Plate them as a side dish sliced length wise or whole.
You can also dice them up, boil them with onion, garlic, salt, pepper till they turn from a bright green to a sage green color.
If you have ever worked with okra, you will notice a "slimy" juice. Wash this away, it is normal and some folks do not like the texture. Once you have washed and strained the Opuntia pads, put them in a bowl with some chopped green onion, cilantro, tomato, some finely diced pickled jalapeño peppers, (optional) lime juice, lemon juice, salt, pepper and any other spices you would like to add and you have made are really refreshing great tasting salad.
If you want to step it up a notch, add some raw shrimp and a sturdy white fish like snapper, the lime and lemon juice will "cook" the fish turning it into ceviche. This will take about 2-3 hours of marinating in the cactus salad, which will also infuse the salad with more flavor.
You can also cut the pads into thick long strips and pickle them. You will find this in the stores in your Mexican food section and it is called Napolino or Napales. Get a jar and give it a try, it is really good and I can eat a whole jar in a day. If you like pickles, you will like Napolino.
Now know that Opuntia is good for you. There have been some studies that show that that it will lessens low density cholesterol. It is low in calories and sodium, high in fiber and vitamin C. It also helps control blood sugar and it is rumored to reduces the effects of a hangover if eaten before drinking.
Besides avoiding the spines, which seems pretty obvious; never eat any part of any cactus that has white sap. If the cactus you are picking has white sap, you do not have Opuntia but some other cactus.
So in a city foraging scenario, the Opuntia is easily found and often people will not think of harvesting it. Do not make it obvious that you are harvesting this plant. Maybe harvest when people activity is at a low or possibly at night. It is natural for people not to look at this plant as a food source. This is mainly due to the hassle from the thorns and glochines. So this is a plus for you in that it will give you a good food source in lean times.
City Foraging Map
My advice is get a map of your local area and mark it with your cactus finds. You want a map of about 2-5 mile radius. A great place to order your maps of the area is http://store.usgs.gov. This is where I get our maps. A 1:24,000 scale should do, but if you can get even closer, that is better. Check your local gas stations, they often have a map that are closer in scale and easier to mark.
If you have a handheld GPS with software, you can go around your neighborhood and make waypoints to all the cactus and other edible plant sources. This way you know where they are located and when you need to harvest, you can harvest a little bit from each plant so as others do not notice that the plant is being picked. Mapping this out will help you in your harvest and also prevent you from over harvesting a food source.
For example, on day one you can take harvest route one that you created on your computer using your GPS software. On day two take harvest route two, again from the mapping software. Doing this will also help you so that you do not get "picked off" from other people seeing your food sources and you gathering and foraging in the city.