Identity of large cactus in a tree

[cosmicaug]

Hi,

I was wondering what this cactus is that is hanging from a tree in the backyard. The location is Winter Park, Florida which is, more or less, a suburb of Orlando (so central Florida). The tree is a large camphor tree.

My photos should link to a larger version (sometimes not that much larger) but you probably won't be able to see much because I used crappy equipment (a webcam and a cheap smartphone).

The cactus is growing high into the tree (15 feet --maybe much higher as I am not good at estimating distances). This is what it looks like in the tree:



The cactus continues quite a bit higher than what that photo captures (not that one can get a good idea without having a good frame of reference). It does not grow from the soil but it seems to be trying to reach into it. I suppose it is possible that the previous owners might have chopped it down at the base and that it had started at the soil at one point.

I did pick up a piece of it (I intend to use it as a cutting). It has three ribs. No more. From a distance some pieces seem flat but looking more carefully from all directions the same three ribbed shape is apparent. As one might be able to appreciate even from my poor quality photo above, most main segments are much, much longer than the piece I grabbed. See the following two pictures:





There seems to be another developmental pattern which is much thinner and with a round cross section (at least assuming it is the same plant --I suppose I cannot entirely rule out that I might have two separate epiphytes).

The spines are severely reduced both in number (to two per areola) and in length. In fact, the piece I grabbed I grabbed with my bare hand and twisted off (I could feel the spines digging in but it was tolerable). The presumed earlier stage with the rounder cross section has numerous spines on the areolae (about what you'd expect) and they are longer.

Here are some attempts to capture the details:









As for flowers and fruits, there aren't any right now (probably not surprising since it's early in the year).



So what is this thing?

[CactusJordi]

Most likely that is Hylocereus undatus.

Jordi

[cosmicaug]

Most likely that is Hylocereus undatus.

Jordi

Thanks!

I had a bunch of guesses, from the very bad (Acanthocereus tetragonus --what can I say, I liked the idea of it being native even if it's not supposed to grow this far north in the wild) to the better (Selenicereus spp) to exactly Hylocereus undatus (someone suggested this and then I realized that I had been ruling out this ID by comparing it to a H. guatemalensis or H. guatemalensis X H. undatus hybrid rather than comparing it to a H. undatus specimen) but I didn't want to bias someone replying.

How do I go beyond a presumptive ID to a more positive ID? What do I look for? I'm very ignorant about this sort of thing.

By the way, happy St. Jordi's day!

[greenknight]

You're right about one thing - Acanthocereus tetragonus is a really bad guess.

Try to get a picture of the flowers to get a positive ID.

[chirpie]

Get out of that tree, right now, cactus! What are you doing up there?

[cosmicaug]

Get out of that tree, right now, cactus! What are you doing up there?

Actually, I think the people who were here before might have wanted it gone.

It shows clear evidence of having hacked at. What has saved it is probably the fact that it reaches so darn high up.

[cosmicaug]

Ha! Look what I found on the ground by the base of the tree!

CAM00068.jpg (90.3 KiB) Viewed 2071 times

I will dig it up and try to grow it so that it will become a fruiting plant.

I have tried to use the piece I took off the tree as a cutting but it's not looking too good yet. I think it will work but it is really slow and I already had issues with rot. After a bit, I thought my first try looked bad so I dug it up and found rot so I fixed it by cutting off the rotting base plus a generous margin. I doubt that it has issues with rot now but it still does not seem to be prospering so I think it may be taking a long time to produce roots.

It will be good to try with something that already has roots!

Though, I suppose if I want a try to planting an undetermined H. undatus cultivar I could just as easily try to decapitate a grafted cactus with the appropriate rootstock and see what it does.

[nona]

I will dig it up and try to grow it so that it will become a fruiting plant.

I've been told they are not self-fertile so you may need two of different stock
and hand pollinate before they will set fruit. (Can anyone confirm this?)

[CactusJordi]

Right, one has to hand-pollinate them. But usually they set seeds/fruit with only one plant. So this species seems to be self-fertile. At least the one in my yard.
Jordi

[cosmicaug]

I will dig it up and try to grow it so that it will become a fruiting plant.

I've been told they are not self-fertile so you may need two of different stock
and hand pollinate before they will set fruit. (Can anyone confirm this?)

I think that you have been told correctly but there are definitely many cultivars that are self-fertile. See Table 2 at http://edis.ifas.ufl.edu/hs303.

In this instance, assuming the tentative identification as Hylocereus undatus is correct, I would be still be dealing with an unnamed variety (I know neither what this is nor how it got here) so I would have to assume that it requires another one of a different stock to pollinate. However, I had been planning to grow pitayas all along and so I should be able to achieve pollination with the plants I have already bought. It would be inter-species pollination (as the small plants I purchased are H. megalanthus and H. guatemalensis) but I am guessing it should still work.

As for manual pollination, I have read conflicting accounts on this. Perhaps it increases fruit set and fruit size but is not strictly necessary? Thomas Osborne, MD at http://tastylandscape.com/2013/07/30/ho ... -to-fruit/ tells a tale of trying to hand pollinate without success and then giving up the next year at which point he started getting fruit. I cannot help but think that if he had not given up on it he might have ended attributing his fruiting success to his efforts at hand pollinating.

I do find it interesting that this plant is supposedly hardy for the USDA hardiness zones 10a-11 whereas I'm probably at 9b (I'm a little bit north of Orlando) and yet it looks like this cactus was definitely thriving. This thing on the tree is huge but the color is not great. It looks a green that is more pale than what it should be, I think, but I suppose that is due to having been disconnected from the ground by the previous residents.

[cosmicaug]

Three years later it produced a blossom.

This is something I did not think I would see for two reasons:

• Most of the cactus is 20 feet in the air and, even if it bloomed occasionally, blossoms would be easy to miss.
• I did not think that the cactus looked healthy and thought it may not be capable of blooming.

I think the poor appearance of the plant was due to being a very large plant which suddenly got separated from the soil. However, in the following years the adventitious root system seems to have strengthened and compensated for that initial trauma as it is clearly thicker that it was and it clearly reaches into the ground and the cactus looks healthier.

As for the fact that most of the cactus is so high above the ground, some high winds managed to shift part of the cactus around so that a branch ended up a little bit above eye level. This is the branch that produced the blossom.

The bud before blooming was slightly over 12 inches in length. The blossom when it opened up was probably about that wide (though I did not choose to measure it so it is an estimate). I attempted to fertilize the blossom when it opened. It produced abundant pollen. However, this is likely a non self fertile variety and it failed to fruit (I think the stem end of the flower dropped today —though it may have happened yesterday).


The day before.



The day of the unfolding (during daytime).



Blooming!


Blooming!


20 hours later.


A week later. In retrospect, I see that it's the wrong color but it actually felt firm.


2 days after the previous photograph. It's gone!

[greenknight]

The flower looks right for Hylocereus undatus - and it's a night bloomer, the flowers usually last just one night. I'd say the ID is confirmed.