Sunday, March 30, 2008

Reasons for plant collapse in Phalaenopsis

Recently I was asked about why orchids sometimes just go belly up and how to avoid it. I actually get this question a lot, and finally the light bulb blinked on - post it to the blog so everyone can read it! Silly me. So what follows is my long-winded answer. Hope you find it useful!

I maintain that orchids are not difficult, they're just different. Different rules. And the fact is that people are often exposed to discount store plants that have received poor care...which reinforces the idea that they're difficult.

The most commonly seen problem with Phalaenopsis is plant collapse or withering leaves, which typically is one of two things: (1) water stress, (2) rot disease.

(1) Water stress can be either too often or way to infrequent watering. I'm sure you can see how too little water leaves to dessicated leaves. But too frequent watering or media that stays wet too long can result in an appearance that looks the same because it can lead to the roots rotting. No roots means nothing to take in water with, so the leaves can't survive.

Most orchids, phalaenopsis included, are epiphytes, and live in areas where they camp out on trees. They get plenty of rain, but its breezy up in a tree so they dry off pretty often too. So in a pot they need a porous mix that holds air and water. It also helps to make sure they're snug in their pot (root bound), which reduces the amount of stagnant moisture in the pot.

Water well when its time to water, then let them dry out a bit before watering again. Stick your finger in the pot and feel around. Should be dry at least 2 inches down, then water well again. Also don't let them sit in water (if they're really dry, you can do that for maybe 20min, but not for a day or more like you can do with some plants). Some people put these things in what looks like regular potting soil. I personally think this is a recipe for trouble because it can stay so wet.

When you pick a plant, look for one with lots of hard white (or silver) roots with green (or purple) tips. If you grab it by the leaves, it should be stable and should bring the whole pot with it, within reason. If its freshly potted, or a slipper orchid, or in a heavy clay pot it might not, but it should still feel firmly associated with that pot.

To check for root problems, yank that thing out of the pot and look at the roots. They should be firm and kinda white. If they're dark brown and squishy, there's a problem.

(2) Other rot diseases are less common, but do happen. Again using the example of the Phalaenopsis, if water sits in the crown of the plant, this can lead to fungus or bacterial rots that will kill the center of the plant and the whole thing will collapse. How to avoid this? (a) Don't bother with misting your plants, (b) when you water, just water the media and not the leaves, (c) if you water with a hose (say in a greenhouse), make sure there's a fan that moves air about so the leaves dry off.


Amber said...

Julia I was wondering how you control mealy bugs in your orchids. I have tons of plants in my office including several varieties of orchids. None have mealy bugs except for my Phalaenopsis. They get down into the folds of the leaves. A number of my office mates have lost their Phalaenopsis spp. due to mealy bugs.

SapphireChild said...

Hi Amber,

There are a couple things you can do. First off, I would start by getting a handful of cotton swabs and a bottle of rubbing alcohol. Dip the swabs in alcohol and physically rub off all the bugs you can find. Second, you can do one of two things.

(a) make a spray of 1 part each distilled water (not spring water and ideally not tap water, since both can have odd salt contents), rubbing alcohol, and your choice of Formula 409, Fantastic, or Murphy's Oil soap *at working concentration, not in 'concentrate' form. Spray your plants with that, then spray periodically after (like every week or 10 days) or anytime you see more bugs.

(b) My preferred method is to pull the plant out of the pot (since they often lay eggs down there!) and get rid of all old media. Get a large plastic bag with no holes and place a few spoonfuls of Sevin dust in the bottom. (don't inhale it) Put the plant in and gather the bag closed with one hand, maybe keeping a hold on the plant with the same hand, and pat the bag with your other hand to produce a cloud of Sevin. Do this for about 60 seconds then set the bag aside to let the dust settle. Take the plant out and put it out of the way of pets/kids for a week, then hose it off and repot it. I have done this with cattleyas and been free of mealy for 8-12 months. I don't know if they were re-introduced or the population just took a long time to recover to where I was noticing them again.

jessica said...

I noticed in your article you mentioned that a porous media is best... are there any specific materials that you recommend? I will be repotting my phal soon, and I think the dirt I have holds water too well.

Thanks for all your great advice!

SapphireChild said...

Hi Jessica!

I'm a big fan of long fiber sphagnum moss for phalaenopsis (in the post on how to mount a phalaenopsis I used sphagnum there if you would like to see an image of what it looks like). Remove all old media and any squishy root tissue, then stick the plant in a pot just big enough to hold the roots. Extra space is not necessary. Dampen and fluff the moss then stuff it in around the roots, somewhat snug but not packed so the plant will stand upright. Most big hardware stores now sell small, compressed bags of long fiber sphagnum moss.

Alternatively, some people prefer a small fir bark or coconut husk chunks -based mix. Bits should be ~1/2 inches in size unless your plant is going into a really big pot. Again, pre-soak the mix, then stuff it in around the roots.

If you use sphagnum, the plant can generally go longer without watering because although it dries on the top, it will stay moist in the middle a little longer (but not so much as 'normal' potting soil). If you like to water a lot definitely go with the fir bark mix that will dry out faster.

Hope that helps!