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Comment by zasdffaa | Hacker News Reader

I don't understand, vegetation in that desert is pretty scarce, so what's burning so hot it can kill cacti.

As for the cacti, if anyone reads this who can tell me this is wrong: chop up an existing saguaro into sections a foot or two long then simply chuck them on the ground. They will root then start tillering. Doing this at the right time of year, a few months before rain, will allow them to root then become established.

Disclaimer - I'm not a cactus, or an expert in saguaro. My advice in this area is going to be poor. Especially as I'm a brit who's never been there.

Edit: it's in the article, substantial amounts of non-native grasses. I'm really surprised established saguaro can't cope with that, but I guess they just can't.

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Sonoran desert resident here. Not to be rude, but your comment is informed by some common misconceptions about the desert and cacti that would be cleared up by reading the very good article linked here.

It's a common misconception that the desert is barren with scarce vegetation. Saguaro habitat can include areas which are almost continuously vegetated, including palo verde and mesquite trees and all manner of grasses, shrubs and smaller cacti. There's a good pic in the article of an unburned area that shows this (about 1/3 down the page). Even in less vegetated areas, seasonal rains can cause bursts of growth that then dry out and fuel fires. Certain invasive species exacerbate this issue, as mentioned in the article.

1-2 foot chunks sectioned from a saguaro trunk will quickly die. The plant's "spongy interior" mentioned in the article will dry out if cut like this. Mature cactus can be transplanted but require special care and support as it takes a long time for them to get rooted. I'm not sure if saguaro arms or larger sections can be transplanted independently as "cuttings". Even if it's technically possible its not common as the mature plants are extremely slow growing and relatively fragile. There are also some state laws around removal and destruction of saguaros that would likely restrict a plan like this.

Rudeness entirely deserved, should have read the article more carefully, thanks. Actually the pics I can see don't show much vegetation around the base. It could be that they just aren't evolved to deal with fire ie, dried out bases. Anyway you know your stuff and I don't.

> 1-2 foot chunks sectioned from a saguaro trunk will quickly die. The plant's "spongy interior" mentioned in the article will dry out if cut like this

I'm deeply surprised. Can the ends be cauterised to prevent this?

> the mature plants are extremely slow growing

I understand they are at the start of their lives and end, but I thought in the middle there was a burst of growth, otherwise how could they reach their large sizes?

> There are also some state laws around removal and destruction of saguaros

Hadn't considered this. Very good point indeed.

Thanks for a thoughtful, tolerant reply

(edit: "Sonoran desert resident here". I envy you)

Growth rate is a function of water. If you water saguaro well (but not enough to rot the roots) they actually grow reasonably quickly for a large cactus. But, over-watering can cause them to split so it's a very fine line.

This is one of the reason saguaro (and other cactus) have ribs. So they can expand and contract as they store/use water.

In nature they grow when it rains, which is not that often in their native climate.

Their roots go out quiet a ways, fine roots go out around as tall as the plant is, but they are surprisingly shallow. A large specimen can weigh several tons. This large shallow root system allows them to capture much shallow monsoon rain.

When we moved them, we took off all roots leaving only the large base roots maybe 2 or 3 feet from the trunk. We would have to brace them for a few years before they established enough of a root system to hold themselves up.

>I understand they are at the start of their lives and end, but I thought in the middle there was a burst of growth, otherwise how could they reach their large sizes?

They are really old?

https://www.epicroadtrips.us/2020/tucson_potpourri_1/saguaro...

I've tried to root saguaro cuttings and was unsuccessful. I didn't use rooting hormone. (I had permits to move or destroy the saguaro, each of which had to be tagged and recorded).

Perhaps it's "possible" with some technical or hormonal manipulation but doubt they would grow to full size and somewhat doubt it's possible at all. Otherwise commercial growers would do it (large saguaro for landscaping can be very expensive).

Other cactus (particularly the Opuntia, prickly pears and cholla) will propagate very easily from cuttings and do so in nature.

Yeah, opuntia pads do root easily. I also won't have them in the house any more. Guess why (shudders with memories of pain)

But other columnar cacti do root easily, eg. trichocereus (though it's is a mountainside cactus not desert) and I've rooted a few others of similar shape over the years, so I mistakenly assumed saguaro would as well.

Yep, San Pedro in particularly root really well from cuttings. (I won't ask "why" you were rooting trichocerus lol).

But Saguaro are quite different. They have an internal woody skeleton. I think they are the only member of their genus. At any rate I failed completely to root them and all cuttings died. I've also seen them fallen over but not dead in the wild many times and they didn't root at the point they touched the soil.

It's a completely understandable assumption that they would root from cuttings though as many other cactus do.

That will work with many cactus but not saguaro. They must be started from seed and the large ones can be well over 100 years old.

(source: I moved and planted saguaro professionally for like 5 years).

Another note (in case anyone is interested). I experimented a lot with germinating saguaro seed back in those days and found a method that produces high germination rates.

I fermented the seed within the crushed fruit with a little sugar and water for a week or so. Then dried the pulp and extracted the seed. Then put the seeds in a water bottle with a handful of sand. Then put water in the bottle and shook it vigorously for 10 minutes or so. Then poured it out and dried it. I planted the dried sand/seed together because it was hard to separate out the tiny seeds. Plant very shallow. Mist several times a day and keep the tiny seedlings well shaded with filtered light.

Small saguaro need a "nurse plant" i.e. they will start under a bush with filtered light, and by the time they are big enough to poke through they can handle full sun (4 or 5 years).

I think this method somewhat duplicates passing through an animals digestive tract, then the action of being tumbled over rock and sand during torrential seasonal rain.

> source: I moved and planted saguaro professionally for like 5 years

OK, I'm pretty well destroyed here! Great comeback.

Regarding your germination notes, I would suggest contacting suitable cactus organisations. Here in the UK there's one (british cactus society) also a major cactus grower in Matlock Bath (http://www.abbeybrookcacti.com/) and any suitable over there in the US. What you've got may be valuable info.

re. germination, you might want to play with ethylene as it's a plant hormone associated with ripening and germination - crushed fruit might very well emit ethylene (https://en.wikipedia.org/wiki/Ethylene_as_a_plant_hormone).

I wonder, how do baby saguaro respond to grafting onto vigorous rootstock? Is that a possible avenue?

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