Choice of substrate + problems with root rot

[Linn]

Since I discovered that my newest Miltonia came from the shop with serious root rot, all of my orchids are now under intensive care...
I have a Dendrobium, including a seedling i removed from the large plant, two Miltonias, and two Phalaenopsis. None of them had any roots, but I've given them an algae-based fertilizer to promote root growth, and I can see a few root tips emerging. My phals have longer roots and I think they soon are ready to be potted.

But I wonder what to do to avoid root rot once I re-pot them?
The Dendrobium seedling was doing very well, with long healthy roots, so I potted it in bark, tried to make sure it had plenty of ventilation, and usually only sprayed it every day instead of watering the bark. Suddenly it started loosing leaves. So I took it out, and saw that the roots down in the bark had rotted, while the roots on top of the bark had dried out.

What to do? It seems to me that the substrate itself isn't very good, so maybe I should try something else?
The most common mix I can find in the stores is this bark (it doesn't say which kind) and it seems to be only bark, with no peat or Sphagnum mixed in it.

The air humidity here in Norway is very low, especially now in winter. So I guess I need something which keeps humidity, but also aerates.

[Claire25]

Hi Linn--

I don't think that merely spraying every day is going to provide enough water to your orchids...you noted that the roots closer to the surface on your Dendrobium were dried out and this may be the reason why. As for the unhealthy roots deeper in its pot, are you sure that they were rotted? Rotten roots are going to be mushy and waterlogged...is this what has happened, or are they dead due to having dried out?

In an emergency situation, when a plant is nearly devoid of roots, I have used a "sphag and bag" approach. Rather than making sure my orchid is "ventilated," I actually place a clear plastic sandwich bag loosely over the orchid, covering all its leaves. This reduces water loss through the leaves. Meanwhile, I will have potted the orchid into sphagnum moss, or at least wrapped the moss around the stump where its roots will grow. This method works well--just make sure the moss stays moist and the orchid stays warm but out of direct sun (which could "cook it" in its bag).

In general, your choice of substrate should depend on how you like to water. If bark is all that is available to you, as you say, then you may have to make do with that...but I grow orchids indoors like you do (and in a similarly dry environment) and I have great success using pure sphagnum moss for my orchids. In fact, I have a Dendrobium potted in moss that is currently blooming in my living room window. The moss retains water well, but is also well-aerated...you might want to do some shopping online for it if it's unavailable to you where you live--it's lightweight and relatively cheap to ship.

By the way, make sure that you are watering correctly...you really need to take orchids to the sink and thoroughly soak the potting material (letting water run out through the pot for several seconds) each time you water. And, in most cases, don't water again until the substrate is nearly dry. Superficially wetting the top of the substrate is NOT enough, and it will lead to underwatering.

One other thought--since your orchids are stressed and trying to re-establish themselves, now is not the time to be feeding them fertilizer. Until they begin to show signs of foliar growth, they are not going to be taking up many nutrients from the fertilizer. In fact, a build up of fertilizer salts will actually "burn" new roots and inhibit their growth--which is certainly not what you want to do!

Hope this helps--best of luck!
Claire

[johnblagg]

I like hydrotron and s/h or just hydrotron and then as you say your were doing srapy them to water but I spray several times a day.

I do have dens in the straight hydrotron and not s/h and I do this fot them as well.My catts are in hydrotron in s/h.Everyting gets watered by spraying alone untill time to flush the pots on a weekly basis and then they get flooded well several times and drained.Then back to spraying them to water .I do use full strenght fert mix to spary them each time also.

[Linn]

Thanks for your replies

Yes, the Dendrobium definitely has rotted roots, they are very soft and mushy, and I thought it was so strange because I was very careful with watering, and tried to make sure the bark was loose.

I've tried the sphag-n-bag method, but immediately fungus started growing on the orchids, so after a while I abandoned that method. How I keep them now is in a jar with sphagnum loosely wrapped around the base. This seems to work fairly well. At least there's no more fungus, but the top of the orchids seems to get too little humidity. Unfortunately, I return home from work very late and therefore I can only spray them in the morning and late evening.

Yes, I thought I might try some online shopping for a different substrate. Perhaps I should try potting them in pure Sphagnum, but I thought this easily lead to more root rot?
Hydroton is for hydroponic growing, isn't it? I could try that also. Is it very complicated to switch to hydroponic?

About the fertilizer, this is the closest thing I could find to Rootone, which I read that people recommend. This thing is called "plant help" and is meant to be used on sick plants to help them grow more roots. I have given them this one a week the last three weeks and now I can see some small roots emerging. But perhaps it takes time for the roots to "burn"? Should I stop using it?

I havent heard of the watering methods you mention. I'm afraid I've watered them from the top, but I've been using the skewer method to check the humidity of the substrate.

[johnblagg]

I just use a very very fast draining medium for my dens .Yes hydrotron is for hydroponics but there is amethod called s/h you should look into as hydroponics is not quite the same hence semi-hydroponics AKA "S/H" with this you only have to water once a week and mist once a day .It is very very hard to overwater in s/h and you can water like crazy if you want to ...LOL I do.

I am disabled and home most of the time so I can obsess on my chids but when I do have the time to get out I can be gone two days without worry at all about anything in s/h the top of the hydrotron will dry out but they dont mind and I just spary them when I get home.

go to first rays website for detailed instructions on s/h and supplies.we also have a forum here on ob about it.