Fantastic thread and photo Ray.
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This is a discussion on Orchid Roots Don't Change within the General Orchid Culture forums, part of the Orchid Culture category; As promised in the "keiki-paste" thread, I thought I'd offer some practical evidence of the ...
As promised in the "keiki-paste" thread, I thought I'd offer some practical evidence of the interaction between roots and the root zone environment. Consider this scenario:
A plant is potted up in nice, fresh medium, and gets great care, so it grows big and strong, sending its roots deep into the moist, airy medium. Those roots have "tailored" themselves on a cellular level to function optimally in that environment.
Time marches on, and that potting medium starts to decompose, breaks down into smaller particles, and becomes more and more compact, holding lots of water and starting to restrict air flow to the roots. Additionally, minerals from your water and fertilizers, plus plant waste products are building up more-and-more in the medium. The environment has changed, but the roots cannot.
The green, vertical arrows mark the nice depth that the roots grew originally, but judging by their color and condition, are failing in that changed environment.
You'll note, though, that there are new roots that look entirely different (see the yellow circle) that have grown from the ends of those old roots. Those nice, plump roots have grown with their cells optimized for that environment, even if it is an environment that is bad for the original root system.
One might surmise that the plant will therefore be OK, as it now has well-functioning roots. Unfortunately, while those newly-grown root segments may be fine for that environment, the older root system is not, so will continue to deteriorate, ultimately completely separating those new roots from the plant, leading to its demise.
That is why, when considering repotting a plant, it is best to do so just as new roots are emerging from the base of the plant.
Fantastic thread and photo Ray.
Thanks for sharing this, it will help me to make good re-potting decisions. Am I right that, if the media has broken down drastically or other changes have occurred to really mess up the roots, it's best to just go ahead and pretty much start over (thinking emergencies such as getting a rescue plant) with whatever you want to grow the plant in? I guess you'd have to support the plant with little to no roots until it started to grow them. If so, how would you encourage new root growth?
Thanks Ray. Excellent post and explanation.
Great explanation - I wasn't aware that that could happen with the new root growth and separation! I'm curious, if a plant like a Phal starts to produce more arial roots rather than roots into the medium, does that mean the medium isn't compatable with the plant and you should repot it into new media?
Carol - plant need and "wants" roots; they will always grow them if the conditions are right. The use of auxin-containing additives like KelpMax can help "kick-start" that process.
OA - I am convinced the formation of aerial roots on a phal is not a response to bad medium. A phalaenopsis has a lot of mass riding on a relatively small base. Aerial roots, which you will notice emanate from the plant higher up than right at the base, can serve as "guy wires" to provide mechanical stability. Their formation suggests that the plant has gained enough mass above the medium (i.e., you're doing stuff right) that it needs that extra stability.
That makes sense on the aerial roots - all my big happy old Phals have them.