Agaveville

Sigh. Have to ask you guys again about cold damage. This cardon unfortunately took some cold damage that has just began to reveal itself. What would you guys recommend? I'm reluctant to cut away the top, but if that will give it a chance I will.

Unless it starts rotting down the trunk, I would leave it on for now. The damaged tissue will likely protect the plant from further damage if there is more cold weather in the forecast. I have a hard time seeing how bad the damage is, if the damage is relatively minor the plant will grow through it, if you are really worried that the whole top is toast, then when it gets a little warmer you can think about cutting it off - unless any rot starts spreading of course.

I had one of mine incur some relatively minor frost damage, but right in the crown where the new growth was, and while it set it back a little it grew through it, I can still see where it was, but the plant has grown well over a foot and a half since then.

Generally I agree with Thijs completely.

However, where are you located? The reason I ask is to help determine how much of a chance you have for further frost this year? The damage is fairly severe. Theoretically, the sooner you cut the top off, the sooner the plant can repair itself, and the less chance that disease will set in and quickly work itself down the stem. The problem is, it is still the middle of winter, and the plant won't grow much until late March or April.

It is certainly a dangerous time to damage the plant by cutting it, but it is also a dangerous time for rot to set in. Actually, it is probably already present, as the plant looks like it is starting to mush out where the damage is. Odds are about fifty-fifty on rot, I would say. You can cut it now, then keep the top covered with a clear or semi-clear plastic container until it scabs over. The semi-clear container will let light in. Try to get a container that barely fits over the tips of the spines, and keep it elevated an inch or so over the cut top if you can (three toothpicks can be inserted in the top of the cut plant for this). That is so that the cut can "breathe" and "scab over", so that it doesn't rot. The container must be solid on the top and sides so that water won't get in from rain or sprinklers, and avoid water settling onto the cut top. You might want to dust the cut top with powdered sulfur immediately after cutting it, in order to help prevent disease. Make sure the cut looks clean and firm. If you have discoloration (like when you cut into fruit that is going bad) in the cut top, you will have to cut it again lower down, about two inches at a time until you get a cut that shows 100% clean tissue. Angle your cut about 30 degrees, so that water will not settle in the crown. Get a little piece of old carpet or a bunch of rags to steady the top while you make the cut to avoid getting stuck. A sharp pruning saw will cut through pretty well if you carefully position it between as many of the spine aerioles as you can.

Sometimes, it is better to just leave the plant alone to it's own devices as Thijs says, but the damage looks to me like the rot will continue. So if you are feeling ambitious, do it now.

The Monger

What happens to a cactus when you behead it like this, multiple new arms?

Usually this species will put out one or two arms immediately below the cut, that will eventually cover the cut completely. One arm usually leaves the plant kind of "deformed" for a while, but it too will eventually get covered up by woody growth (after all, this is the world's most massive cactus species! )

The Monger

To me, that degree of damage to a Pachycereus pringlei usually kills it off (nearly half the trunk is affected in that specimen). Mine have all died that had a fraction of that damage. This species is not a great one for making a comeback. But with luck it will branch at the dead point. Just not seen that happen in this species... had a few others make it by doing that, though. Pachycereus marginata is a more cold hardy plant and seems more resilient... to a point.

Funny how the monitor you use to look at pictures can greatly influence your assessment of things. Here on my computer at home the extent of damage is way more obvious. I think the Monger hits it right on the head: better to cut asap and find a way to cover from direct contact with water, and treat the cut with some sulfur. Does leave me worried about general humidity and also be careful to clean your tool carefully (maybe use some rubbing alcohol) between cuts if you have to make more. You may also have to find a way to protect from any other freezing temperatures you might still get.

Geoff has a point too, Cardons are definitely not the leader among the Pachycerei when it comes to cold hardiness and if you get these kind of damaging freezes a lot, it may not be the plant to grow, because I do not think they ever grow past their frost tenderness. A Saguaro would probably do better, but with that one you bring in a plant that is way more sensitive to over watering and only has about half the growth rate (which I am testing side by side). If you are looking for a massive tall growing cactus, maybe you should think about an Echinopsis/Trichocereus terscheckii, which both grows fast and certainly is in roughly the same weight and size class - also branches more readily. Of those three the terscheckii grows fastest for me and also seems pretty cold hardy and here in the desert definitely does not mind lots of extra water - it is actually the full summer sun it has some issues with.

My only experience with complete tip damage on cacti has been with a couple of Pilosocerei which for some reason I tend to forget when going down the list of plants to cover (like last night, when I almost forgot) and in both cases the plant made a new arm just below the cut, one also produced a second arm in that location, while the other is still single... (it was more recently damaged - last year during the one below freezing night I had...).

A little late now, but you know -- the styrofoam cup trick really works.

That is a big styrofoam cup for a Cardon.... you'd need something more like a Styrofoam bucket... I use Santa hats, though this year they were there more for actual decoration...

I'll take the knife to it tomorrow, sigh. Thanks guys. Sadly, I just bought the guy. He was probably already damaged when I bought him, just not showing it. I already have an Argentine saguaro. Will probably get another in the future as well as a real saguaro.