Does anyone actually know if these aren't just standard megalanthus grown in better conditions? Simon, how do you know these flower later, and is it possible it's just due to growing conditions? Megalanthus are very finicky. It wouldn't surprise me if they fruit much bigger when they're in their native environment, which I think is equatorial highlands.
Nate, the Megalanthus flowers much later and I know this from personal experience and from literature. The info is easy to find if you do a search. Also, there are different selections of the Megalanthus and their appearance is very noticeable. Take a look at the pictures I posted with the gian next to a regular Megalanthus. The regular has fine that are closely spaced and are ovoid in shape where as the selected large Megalanthus is rounder and has spaced fins.
I’ve posted several threads with pictures of various selections of the giant Megalanthus including the ones that started the giant Yellow Megalanthus craze when I post about the giant fruit I found in Hong Kong about ten years ago.
I also have a post about Megalanthus crosses but you’ll have to do a search to find it.
You can get slightly larger fruit with good culture but you’ll get much larger fruit if you start with good genetics.
Simon
Thanks for the response Simon. I did search though, quite extensively in the past. I believe The New Cactus Lexicon is the definitive literary resource on Cactacae, and this distinction is not in there. Their picture of megalanthus fruit actually looks like a red undatus x megalanthus hybrid. And although there are many sources online claiming the existence of a giant version, I haven't seen anything definitive or scientific.
I searched through the most recent hundred threads you started, and all I found related to this was pictures from September 2015 of seedlings you were growing. Have you fruited these in the two years since? You may have posted pictures of fruit you bought ten years ago, but that wouldn't prove anything in and of itself, since the role of genetics in their size is unknown. I don't know Leo Manuel, maybe that is a name I should know, but I don't. Have either you or him fruited the giant yellow?
As for the fins, I don't think it is proof that the smaller one has more closely-spaced fins. What if it were to expand to twice the volume? The skin and fins would stretch out, making them further apart, and changing their shape slightly. It looks to me like in your comparison picture they both have about the same amount of fins/areoles, and in basically the same pattern.
It seems very strange to me that an improved version would exist (for at least ten years as you say), which this guy in San Diego (I googled his name and found an interview video) was growing, yet everybody else in the USA was growing the inferior version, and over all this time the improved version, which apparently grows true to seed, has not spread throughout the community. And it just happens to be the most difficult type of dragonfruit to keep happy. I hope you understand where I'm coming from and don't take this for insolence. I planted some of these seeds as well, but I suspect if I get them to fruit, it will be standard megalanthus (which would then leave the question of whether they're simply not true to seed...).
Edit: And the guy in your thread (
http://tropicalfruitforum.com/index.php?topic=5193.msg198893#msg198893 ) who was saying they are real and he is importing cuttings from South America is now selling seeds, which look (or looked... I thought there was a picture before) like the ones that have been showing up in SoCal stores, and which he just so happened to start offering for sale when they started showing up in stores (
http://tropicalfruitforum.com/index.php?topic=26031 ). Two years ago he was offering seeds for sale as well (
http://tropicalfruitforum.com/index.php?topic=18231.0 ), which he claimed gave true to seed thornless (!) fruit. Maybe I'm just being a conspiracy theorist here. Maybe he is importing direct as he says. It wouldn't be surprising that he gets the fruit at the same time the fruit stores do, but like I keep saying, the whole thing just seems really fishy to me.
Edit 2: This guy's explanation (
http://tropicalfruitforum.com/index.php?topic=5193.msg211534#msg211534 ) sounds believable to me, but of course is unproven as well. "I think the fruit you show us is not a different variety of yellow dragon, but a fruit obtained from different technique of cultivation. In Taiwan , the yellow dragon is grafted onto undatus or costarricensis rootstock, giving to the skinny megalanthus a strong and resistant root system. That grafted plants fruits are 250 to 500 g. True giants yellow dragons come from natural hybridization , and are usually between Ecuador and Peru . The diferences with common megalanthus, besides bigger size and production, is its genetic. The fruits are rounder and smoth in Ecuatorian type and -round-oblong and with very short scales in Peru."