Roots appear to grow only on top

[moniluhum]

I have had these two plants in S/H for about a year now. I cannot see any roots growing in the pot only roots on top. The one with less roots in the picture has been repotted in S/H and the plant seems to only want to grow on top. Lately new roots have been growing well but I still don't understand why the root growth. Is this normal.

[78Terp]

My catts in bark look similar.

[k_andreev]

I have 2pots grow like this but nothing to worry .

[moniluhum]

For those with S/H pots, is there a time to repot when there is a lot of algae?
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[raybark]

Algae is an aesthetic issue only, unless it gets SO thick on top of the medium that it restricts air flow.

Roots growing laterally are the plant's attempt to improve its stability by "grabbing" a larger base of medium.

[Missanna]

I had this issue as well and I asked an award winning cattleya specialist.
He said the reasons could be as follows: I am listing as many as I can here for anyone who may have this problem. They may find one or more things that apply.

1 Orchid is potted too high

2: misting the surface and not drenching the pot thoroughly when watering

3: There may be either more air or moisture near the surface. (See below)

If the medium is too dense, the roots will just wind around the surface. They can tell that it's dangerous to grow down and there is plenty of air at the surface.

However: if you frequently mist the surface of a very open medium, the surface will be plenty moist AND airy which is what roots love. Since there is plenty of moisture at the surface, they have no need to search for it downwards.

4: Medium may have salt build up: roots may avoid attaching to a surface with a lot of salts. You can tell if this is your problem if the root tips that do come into contact with the medium stop growing when they touch it.

Anyway, I used to put a thin layer of moss on the top of my orchid bark to try to keep the bits of roots that were exposed moist because I had very low humidity. (I am also a chronic "too high" potter if a cattleya has a stairstep growth habit). On the surface there was moss that was watered as soon as it was dry which was causing the inner medium to stay too wet. (bark doesn't have any capilary action to keep the moss moist, so this was a bad indicator of the dampness of the medium) The roots would stay near the top where there was plenty of moisture and air. I got into that old habit when potting up some seedlings this year and there was one that the roots were going sideways. I removed the moss and they started growing DOWN.

I SUSPECT that you may have sufficiently high humidity for the roots to be comfortable in the air
OR if you are using a type of clay pellet that doesn't have good capilary action, you may be watering often enough that the surface stays wet enough to be comfortable and the roots don't need to do any work to find water
Or maybe you are misting or only lightly watering the surface.

It doesn't look like your plants are potted too high.

anyway, take some of your clay pellets and put them in a clear glass that already has about a half inch in the bottom. Then wait and see how far up the water travels. I had purchased some of these and because they didn't have any capilary action, they didn't work for semi hydro and I ended up just watering them like normal medium. I water about every other day and the roots have gone clear to the bottom and all over inside the pot. If your clay balls don't pull water up, I would suggest cutting regular drain holes in the bottom and just watering it like a normal orchid. You may also want to pull the whole thing out and look at the rootball. If everything is rotted underneath the plant is trying to avoid the disease in the pot by growing its roots away from the disease.

---------- Post Merged at 09:51 PM ----------

I just took a closer look at your photos and I think I can see white mineral deposits on the clay pebbles. If you are using tap water, you need to check your local water reports. Some towns have more than one well with differing tds, so you will have to find out which one goes to your area. Anything with a tds of more than about 200 is unsuitable for orchids. Or if you would like (if it is allowed), you can mail me a small container of your water and I can test it with my tds meter. OR if you live in town that has a hydroponics store, I'm sure you can take some in and have them dip their meter in it. Lots of those places grow tomatoes hydroponically and most likely have a tds meter that they use for their shop.

If you are using RO or distilled water, you are either using too much fertilizer or not flushing the pot with pure water often enough.

An important note on this is that some hard tap water has dissolved minerals that are VERY hard to remove while other minerals are easy to leach. Whatever is in my water buillds up like stone and needs a very strong acid to get rid of it. My aunts hard water (which has a higher tds than mine does) has mineral deposits that easily dissolve in pure water. With the hard hard water like I have, essentially no amount of leaching will get the salts out of potting medium safely while her pots leach out very easily. It just depends on what is in the water. I think mine is full of calcium and hers is full of sodium, but that's only a guess.

---------- Post Merged at 10:08 PM ----------

Anyway, my suggestion is remove as much of the surface medium as possible, top it with fresh medium and immediately start watering with pure water. Be very careful to not break the root tips. They are at a very fragile stage. Also, if you find that there aren't many live roots (I don't think there are because they were probably killed by salt and the pseudo bulbs look very desiccated), just repot the whole thing and use pure water. If you only have a few orchids, you can probably get away with buying distilled ( NOT SPRING) water, but that can get expensive. If your medium does have good capillary action, go ahead and stay in semi hydro. If it can't pull the water up, you will need a more water retentive medium or a reverse osmosis unit to water on a more frequent basis because you're essentially growing in rocks.

[moniluhum]

The pictured plant in S/H is now blooming so healthy. I have since changed to RO water and changed the dilution of fertilizer. There are still roots growing on the top which I think is normal, but I still don't see roots growing downward. The only thing that I think I could change would be the frequency of watering. I flush the plant every time the water level gets low. Maybe if I should water more frequently. The only question is that now that it is Fall is this a goos time to be doing this?

Please let me know and thanks for all the awesome information.

[Missanna]

As long as your orchid is just starting to grow new roots, since you grow under lights, you can repot.
If there is no salt build up in the medium anymore, you can try to bury the emerging roots under a thick layer of moss (this gentleman said about an inch) which may help force them to grow down, but it's so important that they are not being "forced" into a salty medium. Or you can try the former suggestion and bury the rhizome a little deeper but don't bury it too deep because you can get rotting growths. That being said: I've purchased a lot of cattleyas with the old growths buried way down in the medium and they didn't die. What is more important is that the new eyes are not buried. Those and the new growths they make are more fragile. In any case, if the plant seems happy- if each new growth is as large or larger than the largest growth, the pseudo bulbs are plump, and it's blooming, then don't mess with it too much. Orchid roots are like crazy alien invaders and sometimes they just do what they want.