...so difficul to find? There seems to be endless combinations and availability for stonefruits... however, citrus seems to have alluded the commercial market. Does anyone know the reason? Beyond the hassel of pruning to keep varieties in check, what keeps the growers and/or nurseries from "making" these type trees? While I'm no Joereal, I've been able to successfully graft a few varieties together, making my own "fruit salad" trees. I'm just wondering as it seems that it'd be an easy money maker for the nurseries, there has to be some lopsided reason preventing them from doing, or carrying, more...

Perhaps it is because in differences in cold hardiness? If you had a lemon-orange-lime tree, it would be reasonable to expect the lemon & lime portions to be killed the first year without winter protection. Also, most of the general public don't realize there are more than one variety of orange or grapefruit or tangerine, so multiple variety trees may be tough to sell if people have not developed an appreciation for the diversity found in citrus.

I have seen espaliered orange-lemon-lime trees for sale at nurseries here in Houston, but couldn't comment on how well they have sold.

I think there are two major reasons. The first, to which you alluded, is the fact that if you put different species together, one is likely to be so much more vigorous that it takes over the others.

Another major reason is that citrus can carry some pretty nasty viruses and viroids (tristeza, exocortis, xyloporosis/cachexia, etc.), and unless you're very careful to use virus-free material, there is the likelihood of infecting a susceptible variety from a tolerant (symptom-free) variety. Of course if a nursery using registered scions were to make the trees, they could easily avoid this problem.

I wonder, too, if it may just be a market thing, since the market for citrus trees is the tiniest fraction of the market for temperate fruit trees; maybe there just is not enough demand to cause a nursery to want to do it.

For us, its the marketing issue,, in the past I use to do multi-budded trees on a regular basis. Over the past several years they became harder to sell, it seemed that each season we sold less and less of them. It was a issue of the end user wanting something other than what was grafted.. people wanted a certain type of lime or orange instead of what was grafted.. they wanted that type of grapefruit, and that type of lime but not the type of orange... Its almost impossible to speculate as to what the mass of consumers will demand from year to year...
Its the same way with the Apples and Peaches and other fruit trees we grow, I know I'll sell "X" amount of any given type of tree so I'll grow that as a part of regular inventory...
I still do multi grafted trees,, but I only do it on a "custom" order basis..

Yes, thank you...those were the suspicions I had wanted to to confirm. I plan on using much of my UCR budwood order to make some new combo trees for friends and possibly sell any leftovers. Luckily, being where we are, cold hardiness isn't too much of an issue. Rarely do we 'feeze' and if we do, the news media makes a big enough deal of the impending ice age returnet, that most have the heads up to just cover their young trees...