Cut off all the dead roots - yes or no?

[K-Sci]

Years ago I concluded that it was a mistake to remove all the seemingly dead roots when re-potting an orchid that had suffered root loss. The conclusion was based on two observations:

1) After I amputated all the dead roots while re-potting Phalaenopsis with sodden media and many dead roots, the plant often went downhill very rapidly.

2) Sometimes orchids have healthy roots and may even have new roots developing at a point beyond a section that has turned brown and become flaccid.

There is, of course, a point where a root is completely dead and does nothing, but I don't remove all dead roots when re-potting anymore. It seems as though the core of a root can remain alive and at least a little bit functional after the fleshy outer parts have become rotten.

Thoughts?

K-Sci

[Phalaenoptics]

Thank you for this post, K-Sci! This is something I've been wondering a lot myself. I am excited to see this discussion.

[Clawhammer]

My goal in repotting usually is to disturb the plant as little as possible unless there is a major problem. I only remove old roots accidently when removing old media that has fouled (usually on a new acquisition). Dead roots help stabilize a repotted orchid and they do not lead to further root decay if the culture that caused the root decay in the first place is properly addressed. I find that intervening as little as possible in repotting leads to the shortest recovery. There are always exceptions and I'm sure there are OCD orchid keepers that give them the full MissOrchidGirl treatment and they do fine after recovering from the ordeal.

edit: Yes, I feel like people that clean up the roots, especially with H2O2, do it for their own satisfaction, not the plant. There, I said it!

[Roberta]

I tend to not cut. If the outer coating of the root (the velamin) is rotted, you can remove it just by running your fingers down the root, or washing with a hose. If the "stringy" part is still firmly attached to the plant, it can help in two ways. - It isn't as efficient as a good one in hydrating the plant, but can still contribute. That core is actually the "business" part of the root. Also, those old stringy roots serve to anchor the plant in the new medium. It is vitally important, when repotting, to have the plant firmly held in place - if it wobbles, new roots get damaged and can't establish.

Now, it a plant has lots of obviously good roots, trimming old ones won't hurt. But if there are not many roots of any sort, the plant needs all the help that it can get while it heals,.

Another thing to consider... it's not always obvious what is good and what is not. A few black spots on a root does not render it "bad". Paph roots are often fuzzy and brown, so may not fit your picture of "good" but are actually very healthy (and cutting will kill the plant ) When in doubt, don't cut, you can't re-attach it if you guessed wrong.

[estación seca]

I can't often recognize dead roots. Sometimes dead roots come off with a gentle shake. I never cut them off otherwise.

[Leafmite]

The best way to recognize dead roots from live roots is to soak the roots for a few hours after removing the medium. If any become plump, these are alive. The ones that stay flat are dead. I usually remove all the completely dead roots by just pinching them off. After, I let any living roots heal for a few days before potting the orchid in medium. If there are no living roots, I fill a basket pot with wet NZ sphagnum moss, wire the orchid on top of the medium, then place the entire thing in a clear bag and sit it in a bright (out of direct sunlight), warm place. If an orchid cannot replace the water lost through the leaves, it is important to minimize that water-loss.

If you are getting Phals without good roots often, perhaps it is time to find another source. I

[katsucats]

If large sections of the velamen are black and rotted, and oozing liquid, then I cut them off with a clean razor. If there's little bits of rot on the tips, or if there are dried sections, or if the roots look somewhat degraded but not black, I leave them. When in doubt, leave them.

I've seen, on Facebook groups and other places, well intentioned people watch a Miss Orchid Girl video and start prescribing to everyone to "cut dead roots". People who are asking these kinds of questions typically don't know what dead roots exactly look like, so they read general descriptions and cut off all non-green roots, or all brown roots, or all roots that aren't plump. Then they wonder why their plants aren't thriving.

I once saw someone with a Vanda specimen ask how she could transplant her mom's orchid. Someone told her to pick out all the medium and cut off dead roots. She cut off 90% of the roots!! I cringed so hard I had to leave that group.

[Shadeflower]

my approach is to cut any that are hollow including the stringy bit inside. Sometimes you will actually find that the stringy bit is still green and alive but without the velamen the stringy bit cannot survive, I've tried it, so it might hydrate the plant a little longer and the stringy bits are not really a rotting concern but if they have lost their velamen coating then it is just a matter of time before that root dies off.
The big problem I have with hollow roots like these is that they absorb as muh water as spagnum moss. When you have hollow roots and you squeeze on them chances are water will seep out. What this does is essentially like adding a chunk of moss to the pot and so too many dead roots will affect the moisture level in my pot and risk rotting my healthy roots.
So for my way of growing I cannot have too many dead roots in the pot or they will be a risk to the healthy roots. Otherwise I couldn't really care less if they decompose in the pot or not.

I don't follow a strict dry/wet cycle so in a dry wet cycle this might be much less of an issue if the dead roots are let to dry completely. Just like moss is not an issue if it doesn't get too wet.

But the way I grow, I pick the substrate to maintain the right humidity level. If you grow like this the level needs to stay fairly constant and dead roots make the pot wetter. It is even an early indication sign for me that something has changed in the pot.

But I have had a few roots rot away with no issue, as long as the substrate is not affected too much it should be ok to leave some dead roots.

Recently I did inspect one of my recovery phals. This phal has some kind of issue, all growth stalled, roots stalled and bottom of stem in black. It's not uncommon for a phal to have a black base but on this one the blackness seems to be spreading. So I decided to cut the black away. I even resorted to using 0.5% hydrogen peroxide and the thing did start fizzing indicating it has got an active infection which was growing as slow as the roots and every time a new root was forming the black rot would inch a mm further up the stem and consume that one too.
Would it happen to another grower who lets their orchid dry out periodically and thus anything attacking the orchid dry up too? Possibly, that is one thing I do wonder.
The reason I try to provide good humidity to start with is because those conditions make an orchid grow roots but those are exactly the kind of conditions that let roots rot and whatever black rot on the stem thrive too.

When it happened I assumed I was overwatering my orchids, ie keeping them humid, the stem would rot and the orchid would die.

However having grown enough orchids by now I can safely conclude that a lot of cases I assumed I had overwatered actually had an infection in their root zone and keeping the orchid very humid activiated it to spread.

Bottom line for me is to get a healthy orchid in the first place where this is not an issue and then one doesn't even have to worry about cutting or not cutting any bad roots.

[K-Sci]

It looks like the consensus it to leave the dead roots, and if some are removed, remove the minimum.

It seems clear that if any roots of a plant are rotten, the microbes will have contaminated much of the the media and handling both the roots and media will inevitably spread it everywhere.

I've never used H2O2 on an orchid. Not because I'm opposed, but the idea never occurred to me (I tend to be rather old school).

While it seems likely that a dip in H2O2 will reduce the microbe population, I don't believe it could come even close close to getting it all. A dip in H202 is unlikely to clear the infection from infected roots, so unless roots are cut back to leave only healthy tissue, the rotted root material left behind will supply all the microbes necessary to continue the rotting if conditions persist.

That said, I think the rot in dead roots is primarily saprophytic - an effect rather than the cause of death. As dead root matter is broken down, the water in the velemin is released and the root is no longer taking in moisture. The result is to reduce oxygen availability in the media further, reducing oxygen and potentially causing more roots to suffocate.

H202 will fizz in contact with anything it can give an O to becoming H2O. It doesn't discriminate between dead or live microbes or root tissue, or organic or inorganic molecules. The chemical reaction doesn't include a "live tissue detection" process. I also can't imagine that H202 in concentrations strong enough to kill microbes wouldn't have an effect on growing root tips (speculative).

I just re-potted a C. Walkeriana removing the dead roots, but it had many dozens of live roots and only 5-6 dead ones. Mainly, my goal with removing the dead roots was to help with getting new media into the interior spaces.

K-Sci

[estación seca]

Microbes that attack plants are already everywhere. Being obsessive about cleaning potting surfaces doesn't make sense from the point of fungal nor bacterial prevention; it does make sense for virus and water mold prevention.

Plants have evolved mechanisms to prevent infection most of the time in their normal environment. Plants don't often become infected with microbes unless ambient conditions are not correct. Living in a hot and humid climate, keeping plants in a tightly closed, warm, humid greenhouse or terrarium, or growing them too cool does promote fungal attack in many orchids, because many of the plants we grow don't face those climate issues in habitat.