Here is some pictures of Opuntia ficus indica. The first one is from 2009, after I just transplanted it from a colleague's yard in which it had shot up and was unwanted. It did not like that spot (too much sun compared to where it was before), so I moved it to the front yard. That is where the next two pictures are from. The 2nd one is from 2011, as you can see it has multiplied: a storm broke it in two, but sticking the top part in the ground next to the base was - as we are used to from Opuntias - enough to get it to root. The top part actually is doing better (the one on the right), which is clearly apparent in the third picture, which is from today.
The fourth picture is a hybrid agave I picked up at the DBG sale, in the TLC pile so it was something like $2.50 or so... Agave colorata x bovicornuta, it will be interesting to see how that one does.
Those bovi hybrids have been making the rounds for a while. The ones like yours that favor A. colorata are reportedly a tad sun-sensitive, which is odd because the ones that favor A. bovicornuta really aren't. No clue...
I had a mostly shady spot in mind for the agave given that it does not get that big. I also picked up an A. vilmoriniana from the same TLC part of the DBG sale, it was hard to leave those behind at the prices they were asking and I have had great success with all the plants I have bought in the TLC area, aloes, cuttings, what not. My other buys were two big Mammillarias and a Creeping Devil, which is a cactus that has always fascinated me and turns out to be a pretty interesting cactus from a scientific point of view. Now of course I have to find a spot for it.
Attached a couple of golden barrel pictures... 4 years apart, but in my mind still pretty impressive growth, it is starting to outgrow the planter it is in. Especially since the Ferocactus gracilis next to it, has not grown much whatsoever. The fact that the golden barrel has grown so much seems to almost suggest that it shrunk, but it did not, it also grew a little bit. The F. gracilis was ~30 years old when I bought it - I got it at the annual sale of the CACSS in 2008 and I spoke to the owner of the nursery it came from and he told me he planted the seeds it grew from himself - such patience... It is not a grower, but it does flower every year at least once or twice and when it is wet those red spines are gorgeous.
Nice! Golden Barrels grow like hell if they get watered every now and then. I have a small isolated spot with a Golden and a Fero and nothing else. They were about the same size a couple years ago, but like yours, the Golden is more than twice as large now. Pretty peculiar really, since the Fero should eventually grow to 10X the Golden's size.
A while ago I came across a study done at the University of Arizona looking into growth rates of Compass and Fishhook barrels which are among the faster growing Feros, but they still do not grow very fast, up to a several inches a year depending on rain, but usually at most 1-2 inches/year. But they last a long long time. Some of those 6+ footers are really really old.
I have a 5 foot Compass barrel that I rescued a few years ago, it is doing its leaning towards the sun thing so I have had to build a support for it, but this year it put on at least 2-3 inches right after those good rains we had here. I can easily see it on that one since its crown is rather misshapen. There is a yard in my neighborhood where they have two which are also at least 5 foot long, but probably a little bit bigger, which have become completely recumbent, they look healthy, and clearly did not break when they went to the ground (which I have also seen a couple of times).
Your post has made me go through a lot of my plant pictures and I realized I do not take pictures enough of the plants themselves usually I have 10s of pictures of the flowers, but very few good pictures of the whole plant, which is a pity because it is a great way to keep track of the plants growth and also to some extend its health. I shall have to become better at that.
The golden barrel is one of the hardest for me to grow, also. I've had a half dozen or so smaller plants that have died on me. I've had this larger one going on three years now. I'm still trying to keep a smaller one alive. Hopefully I'll get it right this time.
I guess that I am just lucky. Here is my big Golden Barrell measuring in at 13" high and 16" across and healthy as can be. And I have a lot of smaller ones because I enjoy them so much and they are all doing well. I don't do anything special except fertilize them in the summer and give them water when they dry out. But they are outside all winter sitting in the rain water. But I do cover them up during the really cold weather - 28 degrees or worse. Xuling