Wednesday, February 19, 2014

Random plant event: Cereus peruvianus

I have two very tall, weak Cereus peruvianus. They've been with me since 2004, and for some of that time, I have just plain not had a good bright spot to keep them. Because of the lack of light, they get tall and weak, and because they're tall and weak, the number of possible locations is reduced, so it's this whole unhealthy-cactus vicious cycle.

Currently, the only location available to them (without cutting them down, anyway) is in a corner of the plant room, where the ceiling is 10 feet (3 m) high, as opposed to the 8 feet (2.4 m) or less everywhere else in the house. (More on that decision here.) The cacti have been okay there -- they're not growing much, and they're covered in cobwebs, but nevertheless they stay alive and grow and stuff. So occasionally it happens that, because they're right inside the door, we accidentally knock them over when we're bringing big things in or out, and because they are weak from being a little light-starved, when they get knocked over, it usually doesn't end well for them. Or for us, either, because there are not a lot of things that will ruin your day like a cactus falling on you.

So the last time this happened, it was with the taller of the two plants. When it hit, it landed on the edge of a shelf, so it basically snapped itself off at the point of impact. I straightened it back up, threw out the piece (I was tempted to propagate it, but I already had one cutting, from when the same thing happened with the shorter of the two plants, and I didn't see much point to doing another. I think this was also during a period when I was feeling unusually purgey w/r/t the plants, because of scale, or because I was tired of moving them in and out all summer, or something like that.), and waited for it to resprout. Which it did, in two places, up at the very tippy-top of the plant. And now one of those branches has reached the ceiling, meaning that I need to make a decision again about whether or not to start a new plant from it BUT WAIT THAT'S NOT WHAT THE POST IS ABOUT:

The post is about this:

One of the new branches is also producing roots, about nine feet in the air.

I knew that lots of plants (Monstera, Crassula, Chamaedorea) can produce aerial roots, including quite a few cacti (Selenicereus, Hylocereus, Schlumbergera), but it had never occurred to me that this was something that Cereus might do. How often would it really get the opportunity in the first place? It's not like they grow next to trees that they might attach themselves to, or anything.

So I figure I pretty much have to try to propagate now whether I want to or not. I mean, this is meeting me way more than halfway.


Julie said...

This plant is just thinking ahead...IF IT might need to attach itself somewhere! Hehehe. Have fun with it! I've given up anything thorny these days. My bad.

Melody said...

I agree with Julie. I don't think they are aerial roots, just roots that happen to be growing in the air currently, but are seeking the eventual ground that it would wind up on with a serious break. Look how hard it's trying, you basically have to propagate it now! I'd trade you something for it, but it looks like you're still in getting rid of things mode.

Claude said...

Well, if i was a cactus that kept getting knocked over, i might consider rooting to a nearby wall out of shear desperation... or maybe its just bored and seeing what it can get away with.

Paul said...

Too bad you can't put them on a trolley/flatbed that you could roll outside in the summer and back in during the winter. Doing so would allow for far more intense summer light and tighter/stronger growth. In the winter a chilly spot with little to no water would create a dormant period during which no growth would ensue.

I would agree that these are aerial roots in the typical sense of a Ficus or such but rather roots simply appearing at a joint in case soil might be found. Don't forget that some of the tall columnar cacti are adapted to cascading/leaning or even floppi9ng over and then rooting from the area then in contact with the ground.

Peter said...

Actually there are climbing Cereuses, so it could be an aerial root. But it looks more like its expecting the top piece to break off and fall down so its prepared in advance to root into the ground when it gets the chance.

Jon said...

I agree with Peter and Paul, I bet its anticipating falling over/breaking off at some point. Probably hoping for the wind to blow it just enough away from the parent plant to create its own civilization.

Unknown said...

I've seen this sort of thing in large cacti before. I suspect that once the new branch reaches a certain size, the link between the areole it sprouted from and the water transport channels in the main stem can't feed enough moisture into the growing part of the new stem to keep it happy.

Your indoor growing conditions are considerably more humid than those cacti experience in the wild, so I think the roots are an attempt by the new branch to suck in more moisture from the air to sustain itself.

In the past, I've actually seen plants where the entire older stem essentially "sacrifices" itself to keep the new top growing, becoming more and more shriveled over time, while the new growth remains plump and firm. Your plant does not look like that, in fact, if anything the new growth looks water starved, which is probably why the aerial roots have appeared. I suspect the connection between the two parts of the plant is just inadequate, and the joint might well fail at some point.

Perhaps you should consider cutting it off and keeping it as your new plant. You could always try planting the old plant out into your garden in the spring and see how it goes - some sites on the net report hardiness down to 20F, and there is a great photo here: A bonus if it works out would be that you would be much more likely to get flowers on a permanently out door plant!

In general terms dry snow doesn't seem to bother the tough cacti much - rain and soggy feet are much more problematic - you may need to shovel the snow away from the base of the plant in the spring so that there is not too much melt water directly on the root zone. Planting the plant it self on a small rise or hillock can also help - if the core roots are a foot or so above the normal ground level they should establish well. Put lots of drainage material in the hole beneath the plant - coarse road base gravel os ideal and you can also use it to mulch around the base of the plant to help drain water away. Another thing you can do to help the plant establish is withhold water completely in the mid to late autumn - if the plant shrivels a bit it will cope with freezing temperatures better. If you can put a cover or tarpaulin over the plant when you are expecting rain in the autumn, this will help force dormancy and create better winter hardiness. You will probably only have to do this for the first couple of years as the plant will sort itself out once is gets used to not being coddled in a house.

Ciao, KK.