(Probably?) oncidium going pale and drying up

[narquelie19]

Hi everyone,

I used to be a member here ages ago, but have forgotten my username/password since. (That being said, I'm still a huge beginner at this.) I'm rejoining because I'm really worried about one of my orchids and would be extremely grateful for any help.

I got this orchid from my local botanic garden about 3 years ago - they'd had an exhibition and were giving out orchids in unlabelled pots. I think it's an oncidium, but that's as far as I've got with google.

I'd only ever had a Phal before, so I've had no idea how to care for it and I don't think it's ever looked 100% healthy (though it did flower once). I repotted it about 3 months ago and discovered maybe 70% of the roots were soggy/probably rotten. I cut that off and repotted in a bark/perlite medium which my local florist said would be good. (The bark is in much smaller bits than the one I use for my phal, but I don't know if that's a bad thing.)

I also moved house about 3 months ago, so the temperature/humidity conditions have changed. I'd say it's around 22 degrees C during the day and 20 at night.

Anyway, basically it's looking less and less well. Some bits are drying off, and all the leaves are sort of weird and brittle. They're also paler than they used to be. One of the bulbs seems to have a dark bit at the bottom as well. I've attached some photos that hopefully help.

Any thoughts, advice, suggestions on how to nurse this orchid back to health? Thanks so much


Edit to add it was tilting out of its pot before I repotted, and I did my best to repot it straight. It worked for about a month, but it's now slowly falling to one side again...

[vegetalmatter]

Hello and welcome!

Your plant looks very under-watered. Most oncidium types like a lot more water than people think. Wrinkly pseudobulbs are a sign that it is not being watered enough or in a potting media that is not water retentive enough. Smaller pieces of bark is a good direction, but I would even add a good amount of sphagnum moss to increase its water holding abilities.

For me, oncidium types do very well and adapt almost instantly to semi-hydroponic culture. There is a lot of information on this forum about semi-hydro.

[Orchidtinkerer]

Originally Posted by vegetalmatter

Your plant looks very under-watered. Most oncidium types like a lot more water than people think. Wrinkly pseudobulbs are a sign that it is not being watered enough or in a potting media that is not water retentive enough. Smaller pieces of bark is a good direction, but I would even add a good amount of sphagnum moss to increase its water holding abilities.

For me, oncidium types do very well and adapt almost instantly to semi-hydroponic culture. There is a lot of information on this forum about semi-hydro.

I would have to disagree and I would say even now it looks completely overwatered, so 70% of the roots have died, probably all most likely and without roots it will have a hard time absorbing enough water as the top layer tends to dry while the bottom stays wet.
This will look identical to underwatering. But it was created by doing exactly the opposite. There really should be a distinction.

Narquelie, you already identified this correctly and the media still looks unsuited so it won't imprve much as is imo.
A plant with very little roots is very well suited in semi-hydro like vegetalmatter suggest till it grows some new roots as semi-hydro generally keeps the top layer damp where the plant can absorb water. The top layer does need to stay damp though so if it dries too much either spray it daily or add some moss or small stones on top.
Always aim for an airy substrate that stays damp. Clay pebbles are better than people realize as long as they don't dry out too much. If they are let to dry too much clay pebbles can dessicate roots and do damage.

[narquelie19]

Thank you both! I'd love to hear more opinions, as it seems like there's 1 vote for underwatered and 1 vote for over- so far.

I have been watering it less since repotting, as I can still see moisture through the pot a week or more after watering. Obviously I'm not sure if this was the right thing to do.

It seems like the consensus is that I should move it to semi-hydro. Would it be a bad idea to do that so soon after repotting before?

Does it look like I'm doing other things wrong as well (sunlight, for instance)? And should I be worried about the brown areas at the bottom of the bulbs?

Thanks again!

[Roberta]

The answer to "under watered" vs "over watered" lies in the roots. When it was repotted, what did they look like? The plant does look dehydrated (not enough water in the plant).... but that can occur either if it isn't receiving enough water, with good roots, or if it doesn't have roots to take up the water that is there because they rotted due to staying too wet. Determining which it is, will give you the information to correct things. If it lacked roots (due to prior overwatering) then it will improve with the new growth (which will produce a new set of roots) It can survive by drawing on the reserves contained in the older pseudobulbs (which will shrivel more as the new growth is developing, no worries there). If it hasn't started new growth, or is just beginning, that would be the time to get it into its "permanent" home... semi-hydro if that's the way you want to go, or just let it settle in to its fresh bark. Whichever way you go, it's really important that it be held firmly in place, so that it doesn't wobble, which can damage newly-developing roots. If necessary, stake it (wood barbecue skewers can do the job) - if those older parts are flopping due to lack of roots (the overwatering scenario), staking will hold them where you want them

[Steve83]

My opinion...

You will often have root die off when repotting or mounting, due to the abrupt change in the roots' environment.

You primarily need to be concerned with the newest growth and it's associated roots, as resources are meant to be stripped from old growth, due to the inability of them to flower, (if having already done so). If humidity is high enough, older root growth can survive, and new roots may branch from the older roots.

I find this process much easier to observe with mounted orchids.

[estación seca]

The temperatures you mention should be OK for this type of orchid. The plant looks too good to have had that many bad roots. When Oncidiums develop root rot, the rest of the plant normally follows. I suspect you cut off a lot of healthy roots. Oncidiums only make new roots when new growth is forming. Now that most of the roots are gone, it will continue to struggle until it makes new growth with new roots. I recommend people not cut off orchid roots unless they are black, wet and slimy.

[aliceinwl]

It does look pretty dry in the photos. I’m not sure if this applies to your situation, but sometimes when I’m looking at my orchids, I’ll see condensation on the sides of the clear pot, but the bark itself looks dry. At this point it is still time to water: the condensation is from humid air around the bark. If you wait until all humidity is gone before watering, your plant will be underwatered. I’ve found Oncidium types really don’t like to completely dry out like this.

[ArronOB]

I believe your plant is either a Miltonopsis or a hybrid containing a high percentage of Miltonopsis such as Oncidopsis Nellie isler or Miltonidium Bartley Schwartz.

I base this on the pseudobulb shape and the grey/green colour of the leaves, which is really quite distinctive.

I have quite a few of these and related hybrids. If that plant was in my collection I would suspect too hot, too dry and too much sun. My plants often dry out and get into that state due to limited time resulting from my other commitments but they get well again with a bit of care.

[Orchidtinkerer]

Originally Posted by narquelie19

Does it look like I'm doing other things wrong as well (sunlight, for instance)? And should I be worried about the brown areas at the bottom of the bulbs?

Thanks again!

I don't think the watering is your issue, I think its your substrate and since you just repotted it you can repot it again with no harm whatsoever as nothing will have grown yet that could get damaged.
I started with substrate like yours that stayed damp at the bottom and dried out at the top. It just isn't airy enough long term and by that I mean if you were to blow into the top of the pot (not really practically possible with an orchid in it) then in theory, although you can't physically do it there should be enough air pockets and gaps in the substrate that air can pass from the top to the bottom. Very rarely do I find this then dries too much and I just have to add smaller substrate on top to seal some of the air gaps so it retains a bit more moisture which can easily be done if it is too airy. But always aim for airy first. It is tempting to go for more retentive substrate that needs less watering but growing orchids is not meant to be easy to start with, once you have more experience can you then try to experiement so it doesn't need as much maintenance. Semi hydro is fairly maintenance free which is why I like to use it but I only use it to establish orchids, once the roots have grown enough I then stop using semi-hydro. Although this is an orchid that likes to drink a lot and does not like to dry out completely if the substrate is not airy enough this can be a bad combo especially with a bit of cold on top.
You don't need to use clay pebbles, bark will do just fine too but you can buy different grades, generally you get fine, medium and large. fine should only be used as a top layer in my opinion. Pebbles are easier and cheaper to work with but if you prefer bark go with bark, just choose the right size. If you were to go for large you would have to constantly water it as it would dry too fast and likes a lot of water.

So go for medium and fine and use a smaller pot. The more substrate is around the orchid the less the pot can breathe.

If you have kept fish before think of the water that the fish swim in, it needs to be oxygenated with a fish pump. If it gets too dirty in the tank, too hot or isn't oxygenated enough the fish will suffer. If you were to imagine the fish are roots and the water is your substrate you have to think along the same lines, a fish tank needs to be oxygenated because 5 sides are sealed with glass and the top is usually closed by a lid also. A pot can only breathe through the top like a fish tank. Seal it up with too dense substrate and the pot will not be able to breathe properly, the bigger the pot (compared to the orchids rootmass) the more it can compact if the substrate is too fine. In a small pot you need fine substrate so it doesn't dry too fast. It is frustrating not knowing what size substrate to go for and I still get it wrong all the time, sometimes you have to try different things but never be afraid to repot if you believe you can provide better growing conditions. A repot generally only stresses an orchid if you damage the roots like if they have attached themselves to the pot side, again with fish the perfect example of a stress free repot would be fishing the fish out the water during a water change and doing no damage. Orchids aren't living animals and don't feel as such, they can feel temperature, light and if they have been damaged, thats about it, as long as you don't snap, bend, break any roots whether you repot it, it will hardly know.

I have mentioned how important the substrate is because it is generally not overwatering that causes roots to rot. Like it is very difficult to overwater a bareroot orchid for example. What causes roots to rot is when they get too little air, they need to be able to exhange gasses on a daily basis, compact susbtrate that stays too wet prevents this air exchange which leads to roots rotting.