# Thick and thin roots



## Stone (Aug 13, 2013)

Just wondering if anyone has noted a difference in the potting media requirements between the thin rooted species such as hang, henry etc and the thick. Eg: should a finer mix be used for the finer rooted species? What is the adaptation of thin roots as opposed to thick ones? I notice that, for instance, sanderianum has quite wirey and thin roots and usually grows with very little organic matter on sheer rock faces (but always wet). Am I correct in thinking that the thin rooted species are more sensitive to dryness or need more air or both??


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## keithrs (Aug 13, 2013)

I've always thought it has to do with surface area. I've noticed that thin root plants tend to send out more roots.


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## Chicago Chad (Aug 13, 2013)

I can only comment on my plants responses to potting medium and root growth as opposed to in situ. I have found that my stonei, which has very wirey roots does very well in a finer mix as opposed to something chunky such as coconut husk. I water more frequently as a result.
My hangs do better in a chunkier mix, but not necessarily big pieces of bark, but rather a denser makeup. I believe most of my parvis do well in a chunkier mix. Mine consists of roughly 30% med Orchiata bark, 30% shredded sphagnum 15% perlite 15% grow stone (recycled glass composite). I also use broken packing peanuts for aeration. I use plastic containers and grow in terrariums. 

The smaller mix consists of the basically the same but with finer pieces of sphagnum and smaller sized bark. I will usually use a thin, but incomplete layer of sphagnum on the tops and bottoms of each container to hold in moisture.

So for me:
thicker- cochos, parvis, brachis, callosum, phili., sukhakulii, venustum, 
thinner- sangii, stonei, Wilhelm., 

I'm sure that others culture will very.


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## wonderlen3000 (Aug 14, 2013)

I found it thick root species (all brachy, some parvi, most multi) are very prone to root rot and more sensitive to wetter medium. I normally pot them in medium bark mix. Most thin root species like from section paph and barbata are more forgiving in wetter/or dryer medium, and also they tent to recover more quickly incase of root loss. I think prob because these two section are from moonsoon belt with prolong raining season and then dry season.


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## phraggy (Aug 15, 2013)

A simple rule for all orchids is--- small roots require water---large roots require air ( a dry period )

Ed


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## Stone (Aug 15, 2013)

phraggy said:


> A simple rule for all orchids is--- small roots require water---large roots require air ( a dry period )
> 
> Ed



So you're saying same mix more water for the thins?


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## Rick (Aug 17, 2013)

Seems like I don't consistently see thick or thin roots based on a particular species. For me the older plants seem to produce thicker roots than younger plants.

Pretty weird right now on my Vandas. Typically they produced roots 1/4 or less in diameter, and now they are producing roots as thick as 1/2 inch in diameter. But these are hanging free in air.


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## Rick (Aug 17, 2013)

Maybe this is one of those situations were the plants are adapting to your assumptions of need rather than vice-verse.

You typically water less for dense mixes than coarse mixes, so for what ever reason you put henry's in a fine mix and water less and they adapt with finer roots.


I have mine in baskets or aircone pots w/coarse mix and water a lot, and the roots aren't particularly thin and wiry (especially as they turn into multigrowth plants).


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## Rick (Aug 17, 2013)

Maybe root thickness has more to do with water storage potential rather than immediate culture.

My bulbos and dendros and oncidium types (plants with pseudobulb water storage organs) always have thin roots compared to my vandaceous epiphytes.


In gross generality my phags seem to have thinner roots than paphs (regardless of potting mix type) and many of them are known for almost continuous water supply.

So maybe your paph species with potential for thicker roots have more seasonal rainfall and potential for long dry seasons.


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## Stone (Aug 18, 2013)

I was potting up a few paphs here and there and it just occured to me that there must be some ecological adaptation for certain species to have thin roots over thick. As has been mentioned it may just come down to water requirements. But this does not hold true for the true epiphytes as some Oncidiums have very fine roots yet can handle drying and Vandas can have very thick roots and also can dry out.
But for paphs maybe the thinner and less hairy roots are more adapted for delving into moist and narrow cracks in limestone?? while the thicker hairy ones more for moss and loose material which periodically dries out? But I don't think I've seen enough mature roots yet


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## Rick (Aug 18, 2013)

There's a picture in Lance Birk's book of a dug up brachy (I think its a godefroyae), that has very thick, almost tuber like roots.

The soil appeared very dense and clay like. The caption suggests that the extensive, thick roots were an adaptation to surviving long dry periods, and the roots were essentially for water storage (since paphs don't have above ground storage organs).


The more epiphytic paphs probably access more regular rain, mists, and dew, but would need storage on a more short term basis.

The thinner the root the more surface area/volume can conduct water faster, but that goes in both directions of loss and uptake. 

In many of the insitu pics of paphs, we often see orchid species (like bulbos, and ceologyne) in proximity that typically have finer roots than paphs, but with psuedobulbs for water storage. Looks like 2 ways to skin the same cat.


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## Trithor (Aug 18, 2013)

I have just begun my annual repot in preparation for Spring which (thank goodness) is looming. We have a very erratic and poor supply of quality bark, so tend to make do with the best that is available at the time. This perhaps does not affect growers with a few plants, but when there are thousands, you need to pot, and pot now, irrespective of what is available. I have noticed that young plants (2 or so years out of flask) show slightly different root forms depending on what they were potted in. Most notable was a batch of PEOY, some were in a coarser bark mix and had thicker more extensive roots, while others were in a finer mix and had thinner roots and less extensive. To look at the plants, there was not too much difference in leaf and level of development. So it would appear that individual plants have the inherent ability to adjust their root structure to a degree as well as natural differences from one plant to the next.


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## Rick (Aug 18, 2013)

Trithor said:


> Most notable was a batch of PEOY, some were in a coarser bark mix and had thicker more extensive roots, while others were in a finer mix and had thinner roots and less extensive. To look at the plants, there was not too much difference in leaf and level of development. So it would appear that individual plants have the inherent ability to adjust their root structure to a degree as well as natural differences from one plant to the next.



I agree that we push a lot of plants to adapt to immediate situations we offer rather than working with their natural tendencies (which probably are not as specific as we would like to think anyway).

Now when I make the observation that you just did, I would have originally looked at those different roots and considered was I watering too much/too little, or is the potting mix causing water retention issues/symptoms.

These days I consider excess pot retention of nutrients promoting a chemical environment around the roots resulting in stunting.


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## Rick (Aug 25, 2013)

While shuffling things around, this henryanum in basket caught my eye. This was one of the first plants I put into basket around December 2010/January 2011. Its been growing and blooming consistently since. This is a 4 inch basket, and the gap between slats is 1/2 inch (about 13mm), so it gives you an idea of root thickness. These roots are also somewhat fuzzy.


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## gonewild (Aug 25, 2013)

Looks like white fungus on some roots and on the wood basket, probably in the mix also? And probably a beneficial relationship.


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## Rick (Aug 25, 2013)

gonewild said:


> Looks like white fungus on some roots and on the wood basket, probably in the mix also? And probably a beneficial relationship.




Not sure how much is in the mix (since its got a lot of gravel in it), but I see this fairly frequently on healthy growing systems. So if not beneficial at least benign.:wink:


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## gonewild (Aug 25, 2013)

Rick said:


> Not sure how much is in the mix (since its got a lot of gravel in it), but I see this fairly frequently on healthy growing systems. So if not beneficial at least benign.:wink:



Probably not benign.
Same situation exists here in the forest. Dead leaf laying next to orchid roots often has a white fungus connecting between root and leaf.


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## Trithor (Aug 25, 2013)

That is amazing! The more I see of paphs in baskets, the more I am convinced that it is the way to grow.(true to form, despite my conviction, I have not moved one as of yet. Kind of silly!)


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## atlantis (Aug 25, 2013)

This is a very interesting thread.

I´ve noticed big differences in root thickness among different plants but I´ve always thought it was related to the species itself.

_P. henryanum_ has been mentioned previously in this thread and, in my case, I find their roots specially sensitive and thinner than I would have expected compared to, for example, an helenae roots. It´s difficult to obtain new roots from them and, when they appear, they don´t keep growing for a long time (as most of my Barbata usually do).
Now they´re planted in a smaller bark based mix and it seems that new roots are easier to obtain but when they appear they don´t grow as long as I see in other paphs that I have.

On the other hand, I purchased a _P. insigne_ hybrid planted in CHC with awful roots (thin, "hairless" and almost rotten). I repotted it in very coarse bark, charcoal and pumice and the new roots are just the opossite: thick and very long and hairy. So obviously the health status of the plant must have an effect on roots appearance as well, mustn´t it? .


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