Cactus flowers bloom once a year

My sister and I have had a barrel cactus for almost 20 years. Two years ago, it had a flower for the first time, the bloom coming as a surprise one day when I happened to go out on our little patio. A year later we moved to a house and had to experiment to find the best location for the cactus.

Its skin turned red, probably from too much sun as all the rain we got made sure it got plenty of water. This time, the cactus surprised us with two flowers. A quick search of the internet yielded this information:

Flowers appear at the top of a barrel cactus only after many years; some don't bloom unti...