Root Trimming

[HudsonLH]

Hi all,

When we root trim the fine roots of our cacti, where do the new roots emerge from? Will they come from the cut ends, and branch out accordingly? Or will they emerge from the apical meristem?

H

[7george]

They emerge from new spots, this can be around the cut or above. Sometimes from the stem if we cut too short or old roots dry up for some reason.

[HudsonLH]

George,

Thank you. Are you saying that new roots can branch out from the trimmed ends? For context, I typically trim 30% of the roots off when repotting but have recently been informed by Asian hobbyists that I should leave two inches behind. The rationale behind this aggressive root pruning is that it will improve root health but I am having some difficulty understanding their thought processes.

Would such aggressive root pruning cause the plant to lengthen the existing roots to compensate for damage? Is it possible for new roots branch out from trimmed fine roots? I am not aware of this but perhaps I have not been observant enough.

H

[Steve Johnson]

The rationale behind this aggressive root pruning is that it will improve root health but I am having some difficulty understanding their thought processes.

Quite frankly, I can't understand why growers want to push cacti beyond their natural limits. If that's the reason for Asian hobbyists pruning the roots so aggressively, they may be getting beautiful plants with unnaturally short lifespans. "Proof in the pudding" example would be if a species under cultivation that should live for about 40 years with no pruning at all dies at the age of 25 due to aggressive (I'd say excessive) pruning. Hard to say for sure without benchmarks on what various species' natural lifespans are. And yes, I'm a western grower, so what I say here could be irrelevant to Asian growers and their practices.

[HudsonLH]

Steve,

I have been grilling (interrogating..?) a local group I am part of for the past few months but have received vague, unsatisfactory replies. It may one of those things in cacti cultivation where though many do it, few know the reason why. For now I will keep to trimming a third of the roots (and removing dead ones) when I repot my collection.

I am not sure that aggressive root pruning will shorten the lifespan of cacti. Why do you say so? Bonsais and fruit producing trees are often aggressively ripped to stumps but can live for decades (and centuries for some bonsai).

H

[Steve Johnson]

I am not sure that aggressive root pruning will shorten the lifespan of cacti. Why do you say so? Bonsais and fruit producing trees are often aggressively ripped to stumps but can live for decades (and centuries for some bonsai).

I'm not coming to any conclusions about this one way or another, but since desert cacti and bonsai'd trees have very different growth habits and growing requirements, it would be interesting to find out if trying to "bonsai" cacti does shorten their lifespan. I've never found the need to trim the roots on any of my cacti, so for me this is simply a matter of academic curiosity.

[HudsonLH]

I am not sure that aggressive root pruning will shorten the lifespan of cacti. Why do you say so? Bonsais and fruit producing trees are often aggressively ripped to stumps but can live for decades (and centuries for some bonsai).

I'm not coming to any conclusions about this one way or another, but since desert cacti and bonsai'd trees have very different growth habits and growing requirements, it would be interesting to find out if trying to "bonsai" cacti does shorten their lifespan. I've never found the need to trim the roots on any of my cacti, so for me this is simply a matter of academic curiosity.

Steve,

I see. Thanks for your input. I’ll keep you updated if I receive any plausible explanations.

H

[nopahl]

I remember reading that thai collectors will trim the tap roots off their tap rooted cacti to make them more water tolerant. They put out more finer roots in response to losing their tap root.

[HudsonLH]

Nopahl,

Yes, that line of reasoning makes sense to me, and I have been doing that with my seedlings for several years now.

What does not make sense to me is the bi-annual pruning of 90% of all roots. I understand why rotted ones are removed, and that some roots should be trimmed so that the fit into the new pot is less awkward. However, the rationale of reducing a cactus's roots by 90% to grow healthier roots reminds me of the myth that frequent haircuts stimulate more (and thicker) hair growth.

H