Orchid roots photosynthesize, too. As long as all the roots are healthy and the media isn't all broken down, I imagine they are just taking the chance to increase photosynthesis. Remember, in nature, ALL the roots are aerial!

-Cj

On one hand it's good that you're getting so many roots. On the other, it's interesting that they're avoiding the pots. It's surprising to me that a bark medium dries out in three days. Are you certain it's dry? How do you check for dryness? Do you use the skewer method? That's the most accurate way in my opinion. Either you water very lightly or your medium may be too damp in the center core. If your medium is drying out so quickly, you might consider watering more heavily and waiting a bit longer to water again. This will give the roots a chance to dig into the medium looking for that moisture.

No such thing as too many roots.
-MB

Hi, rocky. I think some of maybe even all of the "aerial root" production is related to the way your plants grow in nature, and is not a cultural problem at all.

eg you mention Brassavola. These (and many other catts as well, tho I can't think exactly which this second) tend to "climb" -- ie each new pb is put out slightly above the last. That's one of the reasons many people like to grow Brassa's on mounts-- that gives the plant a situation where their "climbing" growth habit fits right in with it's setting.

When B's are not mounted, you can't permanently keep the new roots in the pot, because they appear on the new pbs which are above the pot. Many people try to repot the plant so the new roots are in the pot, and that buries the old pbs too deep, causing rot of the old pbs. (And BTW, I learned this the hard way)

Lots of oncidia "climb" too.

Phals don't exactly climb, but each set of roots is higher than the last, and many get a little humidity from the leaf just above, so they grow along the leaf. I don't see that as indicating a problem either.

So while it may be true that for some genera, roots outside the pot mean the roots are avoiding the medium, it doesn't necessarily mean that for many orchids.

This question came up in slightly altered form about a month ago. I said then: "Aerial roots are nice, and characteristic [of several genera] but to be very general about it, if too many of the roots spurn the medium and head for the sky it is usually a head's up that something is off with the mix." Orchid126 by asking questions re: watering practices is trying to focus attention on what should be at least a matter for concern (until proven otherwise) rather than overlooked as we often overlook so many warnings that our plants give us.

H

Thanks all for the responses. Certainly in a collection of over 70 plants of different species, pot size and potting medium not all dry out at the same rate. I've verified the time to dry when repotting a variety of the orchids. Also, I have a few in clay pots packed with sphagnum, and the feel of the pot surface changes dramatically with drying. With the air circulation and temperatures I'm running 3 days seems to do it; I have to water the Phrags between times.

I water 'til there's a flow from the pot, then return for another watering 10 minutes later. Even in plastic pots, medium and coarse bark mixes don't seem to take up much water.

The roots don't exactly spurn the mix - they run along the surface and over the edge. Root tips coming in contact with the mix aren't burned, they just don't usually dive in. I have an Epicat. Don Herman 'Gold Rush' that has roots 18" long and going; makes it pretty hard to move to a display!

"The roots don't exactly spurn the mix - they run along the surface and over the edge."

Sounds like spurning to me...

Some orchids refuse to wear shoes and like to run barefoot through life. If the orchids are happy and growing, I wouldn't worry about it. On the days you water and fertilize the pots, spray the barefoot roots with fertilizer too.

Brooke

The OP is growing indoors and no longer in a G/H.

The OP states 2 things that leads to an issue of culture.
"I'm growing under fluorescent lights, "
"The medium usually is pretty dry between waterings."

What type of flourescent lights? They have to be of high intensity or have a supplimental light source to be watering every 3 days. The catt family do tend to go shallow with the roots but they don't run along the top of the media either. They seem to be on the hunt; probably for water and also light.

I also grow indoors in very high humidity. The lower the light, (tubes ansd low watt cfls) the more aerials I get. What Cj says about additional photosynthesis. Experimental medium/ sour media also produces aerial roots, ie what Howard says about "spurning the mix". Under-watered plants will also produce aerials in a high RH situation.

Bark is an appropriate media. I would suspect water is out of balance with light. The roots are seeking an alternate water source which would be from the 60-70% RH.

Clara

All the times I have seen "excessive" aerial roots in my collection, I have also found media problems, and rotten roots in the media. You could check one or two to see if the roots in the media are OK. If so, I wouldn't worry about it.

CJ brings up a point of misunderstanding about aerial roots. Just because they are green people think that they are equal to leaves. The green in roots is the result of light activating chlorophyll in leucoplasts. You can do the same thing by leaving a potato out in the light. A minute bit of photosynthesis does take place, but the root is not designed for gas exchange the way a leaf is, so the very best it can do with the amount of CO2 that can make its way in is make enough sugar and oxygen to support itself, not to grow or help the plant. According to high tech measurements of carbon fixation rates, a single square inch of leaf carries out more net photosynthesis than all of the aerial roots hanging off of a large Vanda.

There is no reason to water/fertilize aerial roots on a rooted, potted orchid when you consider that 99% of the water and nutrients are getting into the plant from the pot. A root that is not touching a peice of moist, nutrient rich peice of potting material is mostly useless except for the 15 minutes per week it is dripping with splashed ferilizer. That is why you have to mist fertilize that large Vanda twice a day for good growth, when you only have to water once a week for a potted Phal having only 10% of the root mass.

Is there any reason to keep the aerial roots looking healthy? No, their death does not affect or reflect on the overall health of the plant. Roots are cheap and temporary structures in many plants. A large proportion of cacti roots die back every year, and the only active part of most roots is the first two inches.

What are aerial rots good for? As indicators. They tend to show up most when the air humidity is high (good condition), and when the potting medium is either full of roots or old and decaying (not good).

My light intensities are relatively low, but the plants are close to the bulbs and have good color - medium green with reddish tinge for most Catts. The roots that are down in the medium are alive - they pop root tips up from the sides of the pot into the air!

I think the bark medium (bark, charcoal, perlite) is not wetting thoroughly; when I repot because the plant climbs out of the pot I find the mix has not deteriorated much even after a couple of years. I regard this as a strong indicator it's running dry even with my frequent waterings. I'm considering going to some of the mixes having chunks of sphagnum in with bark and perlite - these should have a greater tendency to soak up and then transmit moisture following watering.

I only have a little bit of experiences to offer
This summer I had one of my sederea japonicas under wetter than normal conditions. There were already tons of aerial roots, but more grew and I thought "GREAT!" but then when I repotted this fall (forced by the pot blowing over the table and breaking, and not out of my own volition), I noticed that lots of the roots inside had died. The plant was healthy enough, which I assume was due to the frequent drenching of the a. roots by the rain. I'm thinking that they grew outside the pot because the media was too wet, and the a. roots actually helped significantly in the plant's survival because it was humid enough during the summer.

Anyway, long story short, I agree with spiced ham: A lot of aerial root grown likely signifies media problems (I've only seen it in too wet situations, since I have never been blessed with high RH). However, in addition to indicators, I think they are important in the situation where if you do end up catching yourself with a rotting plant beneath the media, the aerial roots might be your only chance to save the plant. Aerial roots is better than no roots!

That said, I used to obsess about keeping the aerial roots on my phals moist during the winter so they wouldn't shrivel. They shriveled anyway. At this point, the only thing you can do is keep an extra vigilant eye on your culture practice so you don't lose the media roots you do have!

Once the media gets really dry, water tends to run off and not be absorbed. You may want to immerse a pot for 10 minutes or more to make sure the bark is really absorbing a significant amount of water.

I've even taken a piece of bark from about half way down inside a pot and broke or cut it apart after watering to see if the water has penetrated. Depending on how dry it was, it often has not absorbed much by watering from the top of the pot.

I have been repotting things these past few days and something resonates with rockyfarm's comments. Although it has been only a year or so since last repot, I had roots either winding around the pot rims or out the drainage holes or aerial roots to the extent that I suspected they were not happy. Upon investigating, the bark is very solid and not visibly deteriorating at all. Still, the roots in the center of the pots are rotting. (Until recently, if the roots were rotting, the medium was breaking down.) I can't explain this fully. When I water I usually soak pots, then drain as well as possible. I can't identify any component which has changed, except perhaps the manufacturer of the bark itself.

I also have to disagree with the photosynthesis slant. Aerial roots are a response to heat and dryness (in Clara's case, lowered bulbs = more heat and therefore more dryness). In cultivation, if a plant isn't established, it will seek to secure itself first. If the plant is established but growing in warm and somewhat arid conditions, that would be an incentive to send out exploratory roots. My plants grow in such conditions and all of them, except paphs, have floating roots - phals being especially prolific. If it is established and also happy with surrounding moisture, there's no incentive to send out exploratory roots and it'll just keep grabbing and grabbing. I don't remember seeing many floating roots in greenhouses, which typically provide moisture saturated atmospheres.

So in my opinion, the presence of aerials (even LOTS of aerials) is no reason to assume a crisis. But the plant is asking for something. If I've optimized my watering and humidity, I just shrug my shoulders and try to keep them alive and fed, without losing sleep.

John