Old roots rotting

[Stone]

I have noticed that after repotting a seedling, it often loses its (seemingly) healthy roots (firm but without a growing tip) or at least some of them. I notice this when checking after a few weeks. However new roots are usually not far behind...but sometime they do not come easily! If you take the plant out of its pot you would assume by looking at the mushy roots that it recieved too much water. But I have a feeling this is not the problem as the amount of water never really changes. There seems to be something else going on which causes the roots to die after repotting not the amount of water.
Any ideas? Could it be unseen damage during potting? Soaking the roots in systemic fungicide makes no difference at all. I don't think it is a pathogen problem.

 

[Ozpaph]

I think paph roots just dont like being disturbed and thats why timing repotting to when they are starting active growth seems sensible. (all supposition of course, based on observation).

 

[gonewild]

This is one of the main reasons the low K formula was developed.

 

[Trithor]

This is one of the main reasons the low K formula was developed.

I saw that one coming!:rollhappy:

 

[likespaphs]

it could be caused by a number of issues
the root may have been creased or otherwise damaged during repotting
the root was already dying off as they naturally will, but you only saw it at that stage
but i bet the real reason is Paphs (and many orchids in general) are just kind of mean and capricious

 

[naoki]

Could it be a natural reallocation process? Plants can probably tell useful roots from useless roots (which need to respire, so they are the resource sink). It may be better to reabsorb the resource from the sink root and reallocate it to make new useful roots. When the roots are touching to some media, the root has a longer time to absorb water. But after repotting, the contact between roots and media get broken. The root with growing tips can establish new contact, so it appears that it is a useful root. But the root which wasn't growing at the time may look like a resource sink. Especially when the plants are small, they don't have excess energy, so they have to make quick decision on how to allocate and re-allocate resources. In a larger plant, they may not need to take the drastic reallocation path. We usually see the growth lag after repotting, and the root reorganization may be the cause of the lag.

 

[Stone]

I saw that one coming!:rollhappy:

I can honestly say that I didn't :rollhappy:

 

[Stone]

Could it be a natural reallocation process? Plants can probably tell useful roots from useless roots (which need to respire, so they are the resource sink). It may be better to reabsorb the resource from the sink root and reallocate it to make new useful roots. When the roots are touching to some media, the root has a longer time to absorb water. But after repotting, the contact between roots and media get broken. The root with growing tips can establish new contact, so it appears that it is a useful root. But the root which wasn't growing at the time may look like a resource sink. Especially when the plants are small, they don't have excess energy, so they have to make quick decision on how to allocate and re-allocate resources. In a larger plant, they may not need to take the drastic reallocation path. We usually see the growth lag after repotting, and the root reorganization may be the cause of the lag.

Possible.
Older roots without a growing tip always just sit there and never or almost never form a new tip (although insigne has done it for me) Some will stay firm and keep taking moisture for months and some just rot away. I can't see any difference between them but obviously there must be??

 

[Stone]

but i bet the real reason is Paphs (and many orchids in general) are just kind of mean and capricious

No doubt about it!

 

[SlipperKing]

Mike, have you tried repoting using 1/4 to 1/3 old mix with the new? I have seen better survival of the old by this practice.
Last night I repoted a few parvi and was surprised to see such great roots after a year growing in mostly marble chunks and sponge rock. Very few to no dead roots even thou the majority did not have active tips. One of the Hawaiian growers, I believe QF, has been selling seedlings and BS in mostly sponage rock So I decided to continue the practice to see what came of it. I'm impessed so far given my conditions.

 

[reivilos]

This is one of the main reasons the low K formula was developed.

lol.

Since I've started putting paphs in plastic bags I've been able to make them grow new roots in a week or so. I had plenty of time to observe them.
I stopped posting pictures, but the only paph I have that seems to resent the bags is delenatii.

I've noticed that:
- root tips that get hurt stop growing almost overnight
- root tips adapt to the environment. Aerial root tips will dry in a few hours if exposed to dry air
- the slightest change in fertilizer may make them stop
- roots usually rot from the tip up (unless broken) or soaked
I've seen roots growing new tips or even branch, though. Almost all my Ratcliffe divisions did this.
If undisturbed, root can grow forever. That's the reason why I no longer buy the fertilizer magics argument. There are just too many factors in a greenhouse to single out only one of them;

This plant has been sitting in a closed bag at the same shaded place under a table since July 3rd. I've never watered or fertilized ever since.

then:

 

[daniella3d]

I don't understand, if the low K promote healthy roots why then the algae formula like maxicrop is also said to promote root growth and it is basically just K?

What did I miss?

If going on a vacation for a week, would it be a good idea to put the plants in plastic bag so that they don't dry during the week?

This is one of the main reasons the low K formula was developed.

 

[Stone]

Mike, have you tried repoting using 1/4 to 1/3 old mix with the new? I have seen better survival of the old by this practice.
Last night I repoted a few parvi and was surprised to see such great roots after a year growing in mostly marble chunks and sponge rock. Very few to no dead roots even thou the majority did not have active tips. One of the Hawaiian growers, I believe QF, has been selling seedlings and BS in mostly sponage rock So I decided to continue the practice to see what came of it. I'm impessed so far given my conditions.

Hi Rick, no I haven't tried including some old mix with the new but I have heard of it. Maybe it helps to inoculate the new mix with the various microflora established in it?
I have this old hybrid (Harrisianum) that is always so strong and healthy that I thought about using some of the mix from that. I remember reading once that that used this plant as a mother plant to sow seeds onto in the old days.
Sponge rock we can't get here but there is a new product (I think American) which is made from glass and looks like giant perlite.

 

[Ozpaph]

lol.

Since I've started putting paphs in plastic bags I've been able to make them grow new roots in a week or so. I had plenty of time to observe them.
I stopped posting pictures, but the only paph I have that seems to resent the bags is delenatii.

I've noticed that:
- root tips that get hurt stop growing almost overnight
- root tips adapt to the environment. Aerial root tips will dry in a few hours if exposed to dry air
- the slightest change in fertilizer may make them stop
- roots usually rot from the tip up (unless broken) or soaked
I've seen roots growing new tips or even branch, though. Almost all my Ratcliffe divisions did this.
If undisturbed, root can grow forever. That's the reason why I no longer buy the fertilizer magics argument. There are just too many factors in a greenhouse to single out only one of them;

They are very interesting observations. Thank-you.

 

[Ray]

Roots adapt to their growing environment as they grow. Once grown, the cells cannot change.

An old medium will be different from a fresh medium (except in the case of perlite or LECA, as in S/H culture). The roots that grew in the old medium are not optimal for the new, so they will ultimately fail and need to be replaced by new growth, much as Naoki alluded to. The bigger the difference, the more drastic the adjustment will need to be. Rick's addition of old medium to the new reduces the difference.