Vandas in semi-hydro?

[Ironwood]

Originally Posted by Ray

Plants roots growing down is not an aversion to light, it is gravitropism - an orientation based upon gravity. Moreover, that doesn't really apply that well to orchids, as in nature the roots go in every direction, and usually contain chlorophyll, suggesting they would want to see light, not avoid it.

Actually Ray the aerial roots of my phals growing in a window in a fixed position will grow away from the light.

[Ray]

You're right, Charles. I did misunderstand your point.

Now then...I'll be a bit argumentative here, not because I "know" anyone is wrong (I certainly don't), but to expand the discussion a bit.

What makes us think the plants are growing the roots away from the window in order to avoid the light? Could it be that there are differences near the window and away from it other than light that are affecting it?

(Don't get me wrong. I grow in a greenhouse, so the light, temperature, and humidity are pretty directionally uniform, so I don't see such tendencies, and my earlier comments are based upon the functionality of the plants' structures as well as from observation in the wild.) The point I'm trying to make is that we should not grab a single explanation and consider it gospel. "Too much water causes root rot" and "high-phosphorus boosts blooming" are two examples of well-established "facts" that we know are incorrect.

Let's consider the plant near the window as an example and compare microclimate differences. Light is the obvious one - more toward the window, less away. But what else?

How about temperature and humidity? Near the window the air is heated by the light, which also lowers the relative humidity. Both of those aspects increase the drying of the plant structures, so maybe the plant is growing roots toward a cooler, more humid zone for survival - sort-of a "Maslow's heirachy" thing for plants - retaining moisture is more important than the extra photosynthsis. (Besides, in a dry environment, the velamen will stay relatively opaque most of the time, significantly limiting the roots' ability to photosynthesize anyway.)

If it was winter and I was cold, I might first have thought of "it's colder near the window, so the roots are seeking to be warmer".

My guess is that the heirarchy for orchid roots is 1) seek water and nutrition, 2) grab a strong foothold, with 3) photosynthesis, being a relatively "bonus" feature (except in the leafless ones, of course). Any environmental condition that can have a negative impact on the plant will influence how those are expressed.

Editorial comment: I just love that we can bounce these things off of each other on a friendly basis. In some forums, the conversations can degenerate to the (old SNL) "Jane, you ignorant slut" level.

[adriponic]

good point ray

I have 2 equitant oncidiums (William Thurston) in sh.
One in a 10cm deep pot and the other in a 17cm deep pot.
Both set from flask to cp then to above pots at the same time and same size Obviously the one in the 17cm pot is
doing better after 5 months... about twice the size.

BTW 15 others were mounted on fir bark and cork and
none of these show better growth than even the 10cm
pot. I agree though that these mounted chids get watered and fertilized about 2 times weekly at best.

[grayowl]

I have been growing a mokara hybrid for several years in a mix of leca and perlite, and water once a week or less top down, in a standard container. Sitting in a moist environent(semi-hydro) they rot quickly. They need a lot of oxygen exchange or air movement at the root zone.

Highly recommend "The world of orchids" by Jack Ross about his extensive research into hydroponic culture.

[Charles]

I have had vandas and others growing in a western window and almost entirely without fail, the roots are looking to grow away from the light. Also grown slightly on the dry side as the A/C is usually on so humidity is low. It would seem that the plant is looking for a shady wet place to draw moisture.
I agree. Roots that are started in a certain environment will prefer to continue in that environment. My point is that giving the plant a choice between dry conditions and wet conditions and letting it use what it needs of each is ideal.
I think you have misinterpreted my point. I agree with you and I am also pointing out that reacting to heat and dry may cause roots to seek moist shade.

[Charles]

We have disagreed ourselves right into the same camp on this. I think this is where we went wrong in our discussion...
Quote:
Originally Posted by Charles View Post
(I secretly believe that the plants have two kinds of roots.) Those that find warm wet spots for moisture during dry periods and those that must hang in the air.
Actually, I don't believe a plant has more than one type of root, but if you want to interpret it that way, they can have any number of different kinds of roots. Here's my logic - right or wrong:

It is a well-established fact that root cells tailor themselves to the conditions in which they grow. Based upon that, it's easy to view aerial and "submedian*" roots as being "different".

However, in the case of roots that have grown down into the reservoir of a semi-hydro pot, they are now fully submerged, so are easily a third type.

Now then, think of the last time you repotted a plant that was in soppy sphagnum. The older parts of the roots may have mostly died and shriveled up, but there is fresh, new, white growth below that! Two more "types" of roots.

So basically, one might interpret a root grown under any two different conditions as different roots - and that would conceivably even apply to seasonal variations.

* Think "subsoil" or even "subterranian", but with the generalized "medium" replacing soil. If Ben Franklin could coin words, so can we all!
__________________
Ray Barkalow
First Rays Orchids

I was being humorous about the "secretly believe" part. Roots are roots, but the plants will send them into what we believe is a horrible choice. Simply due to those "irrefutable factoids" we have all come to understand, such as, dry out Vs. air movement.

[Ray]

Charles, I hope to meet you some day and share a bottle of wine or something. I'll bet we could kill an afternoon without blinking!

[adriponic]

Hi Ray, Hi Ken

One saying goes "Good boys go to heaven and bad boys
go anywhere".

Seems to me that vanda roots or others are like the bad boys...

Anyway i'd like to bring one more wine bottle if ever we
could all meet... BTW did you know that the roots of
the grape vine go down up to 30 feet deep in the soil?

Cheers

JP

[Ironwood]

Once again Ray you have pretty much hit the nail on the head, I think the roots know (built in genetics) that they are more likely to find moisture in the shaded areas.

I think we are up to a cask of wine now.

[Buds!]

Has anyone tried Vandas in s/h since this post?