Wintering and dormancy with S-H/LECA culture

[daddydoall]

Wondering how others have handled orchids that traditionally require a winter rest (dendrobium) or dry period and handle colder weather (sub 50F). It seems a constantly damp media even LECA could be a problem with orchid varieties needing a dry period or dormancy and even cause rot in others if temperatures in the green-house stay cool for prolonged periods. I just started using LECA, in normal or open pots and will use trays as a reservoir when it warms up but am afraid of plastic reservoir pots, though I suppose one simply could empty the reservoir and not water till spring?? I live in N California and grow in a green-house. Falls Temps are 50-70f, winter 40-60f. I use bottom heat when air temps drop below 40 (this makes roots grow like crazy).

[Ray]

First comes the fact that the winter rest isn't so much "dry" as it is "nutrient free", which naturally occurs when rains diminish in the forests, so there are little-to-no nutrients washing down on the orchids. Don't forget that many "dry seasons" are less "arid" than simply "not monsoonal".

In S/H culture, there are two schools of thought, both successful:

1. Whothhold all watering, like you would with traditional culture.
2. Water normally, but provide absolutely no nutrition until growth resumes.

[daddydoall]

Thanks for the quick reply Ray,

[mtorchid]

I have two types of deciduous dens in S/H, anosmum and unicum. In their natural environment, even though the monsoon season is over, there is still moisture available in the form of dew and fog.

I switch to a top-down water method during the rest, never letting water stand in the reservoir but still giving enough moisture to the S/H to provide some moisture. If canes or P-bulbs start to shrivel it's a sign that more water is needed. It's wonderful to watch an orchid that looks like it has died (brown leaves) bloom into something beautiful.

[nutgirl]

I started with S/H and was very pleased but as my plants (Phalaenopsis) went into larger pots I had trouble with root rot. Since my growing conditions are similar to yours I moved them indoors in winter but it still was a problem. The root zone was too damp and cool.

I switched them back to regular potting material. Naturally some species love the extra coolness but not the Phals.


Maureen

[Ray]

Originally Posted by nutgirl

I started with S/H and was very pleased but as my plants (Phalaenopsis) went into larger pots I had trouble with root rot. Since my growing conditions are similar to yours I moved them indoors in winter but it still was a problem. The root zone was too damp and cool.

I switched them back to regular potting material. Naturally some species love the extra coolness but not the Phals.


Maureen

True enough. Phals are actually hot growers - in nature many see daytime temperatures over 100°F, and nighttime temps never below the upper 70's. In our households, we're actually pushing them to the lower limit of acceptable conditions. Lower the thermostats in winter and let that evaporative cooling from the open medium get hold of them, and root loss is assured.

[daddydoall]

Thanks, so rot tendency is worse when it is colder and plant is growing slower or in dormancy. That is what I am trying too with the dryer growing Den / LC types, using trays as the reservoir, and removing or flipping the tray in winter and only top watering when LECA starts to look dry. Indoor (warmer) growers probably do not have this issue with most species.

[mtorchid]

An option that seems to work well in Winter is to use seedling heat pads with Phals. It's an extra step, but the roots love it.

[amok]

Hello! I've been lurking around for almost a year now and finally register.

So, other than using a heat mat, any other way to combat the cold weather? At where I live, the temperature finally start to drop this week. After reading this thread, I am a little concern. At what temperature that it will really do damage to the plant?

[Ray]

Originally Posted by amok

Hello! I've been lurking around for almost a year now and finally register.

So, other than using a heat mat, any other way to combat the cold weather? At where I live, the temperature finally start to drop this week. After reading this thread, I am a little concern. At what temperature that it will really do damage to the plant?

That depends upon the plant and the ambient humidity.

Each plant has its own "comfort zone" (or shall I say "survival zone"?). Stay above the minimum, and the plant may slow its growth, but ought to be fine.

If the plant is in a moist, open, airy medium, and the humidity is low, evaporative cooling of the root zone will drive the temperature below that "comfort zone", and damage can occur.