I haven't found any reliable information about that. If you assume that nutrients in solution are absorbed by roots along with the water they are in (which may not be the case), then 20 minutes seems too short. A dehydrated pseudobulb, or a wilting plant, takes longer than that to recover when it is watered. And in nature, nutrients are present in adequate amounts around the roots more or less constantly in the form of decaying leaf litter, dead insects, etc. Of course, fertilization in a potted orchid is a different matter, and periodic flushings between fertilizations could eliminate unused or excess nutrients.

When I water my Bonsai tree's I generally water four times when fertilizing. Fertilizing the third time and then watering 30-60 minutes later which is to help 'take out the trash' allowing the soil to be flushed of unneeded fertilizer as well as chemicals the tree produces through normal growth (which is only an issue since its in a pot and not in the ground). Then again this can be a totally different situation since the soil is free draining, and while some Orchid mixes can also be free draining they are a different type of plant and I know very little about them in that aspect.

While some specific species may need this, I believe that for most orchids, if I water well (lots of water running out the bottom) there won't be a buildup from feeding to feeding.

My 100% inferred from dodgy logic and 0% scientifically backed opinion is this: when you fertilise, the nutrient salts aren't just absorbed by the roots they're absorbed by the media. Each time you water, these salts in the media should re-solublise and leach from the media, supplying additional nutrients to the plant's roots. Granted it's not as much as the initial fertilisation but at least it's better than starving until the next time you fertilise. The rate at which the nutrients solublise depends upon the concentration of salts in solution so each time you water the media, nutrients are released at a decreasing rate.

By flushing the pot staight after fertilising I would think you'd be doing two things: (1) leaching nutrients that have been absorbed by the media so that subsequent waterings will leach less nutrients and (2) leaching out nutrients that have just been absorbed by the velamin. In both cases you're taking nutrients away from the plant. The plant you mentioned, Den cuthbertsonii, is sensitive to overfertilising so flushing excess fertiliser away from the plant straight after fertilising would be advantageous. By the same token, rather than wasting fertiliser by washing away the nutrients straight after feeding them, why not give the plant less fertiliser to begin with?

Corymbosa makes a good point: why not reduce the fertilizer's concentration or even use a fairly safe fertilizer such as fish emulsion?
While flushing soon after fertilizing may help protect the roots of the cuthbertsonii (have not even fertilized mine since purchase several years ago!) a once the week flushing may be more than adequate for most orchids depending upon the quality of water being used. If you are using a R/O system then it is not needed. If your water is unusally hard then it is probably needed.

Good points all.

Honestly, given how much one has to water during the summer, coming back for a second, flushing-intended watering is pointless. Unless you're fertilizing with every watering (which you should be using VERY weak concentrations), your normal nonfert waterings are more than enough to wash away the nasties in the pot. Now if you're dealing with pleurothallids, thats a whole other matter and they should see scant fertilizer to begin with. So you definitely won't be seeing salt buildup with them.

Keep in mind also that many orchids are very slow to take up water. Have you seen how long it takes Angraecum roots to turn green after you water? For orchids like that, 20 minutes is certainly not enough time.

I dont know how a Orchids biology works as far as nutrient absorption & break down work, but the main point of flushing with Bonsai is the point that while the media absorbs/leeches out fertilizer it also does the same with the plants waste, which is formed normally through breaking down what you are feeding it. The flush therefore is used to keep the waste from building up into levels that would be toxic to the tree.

I have never done this before. Once a week or so I water with pure RO without fertilizer, the rest of the time I use a very dilute dosage which is applied to all plants equally. It would be cumbersome to use different ratios for different plants.

I was taken back when this grower who has a good reputation, a great nursery , a masters in biology and chemistry suggested this. I just wanted to know if anyone is doing something like this, apparently not. I will use this method on a few select plants and see if it makes a difference. At the Pleurothallis Alliance meeting in San Francisco this weekend, I ran it past a couple of people but no one thought it was necessary.

It only requires the flip of a valve to switch from RO with fertilizer to pure RO so it takes no effort to water the target plants first and at the end throw the valve and flush them with pure RO. It takes me at least 30 to 45 minutes to water everything so that's the time element we are talking about.

Nick

Geesh it takes me an hour to water my Phal mounts, two hours if my husbands doesn't do the rest of the mounts and Vandas. After that I have to water whatever potted 'chids need it. I must be very slow if you can do yours in under an hour.

I figure orchid roots take up water or water & fertilizer until they dry out. I figure it was one reason Masdies need so little fertlizer since they are moist almost all of the time.

Brooke

Zero scientific info on this, just observations over the last 6 years - admittedly, a scant amount of time.

All my orchids are in sphag and plastic pots, except for the mounties. No Pleuros. For each watering, each potted plant is soaked in a bowl of not-the-best tap water for an hour or so.

Then it drains for about 30 minutes. Depending on the sequence in the watering cycle, the plant's then watered from the top generously with
a. spring water or
b. spring water with fertilizer in it

The 3rd watering is flushing several times with tap water.

Between waterings, whatever liquid's there stays till the sphag's almost dry and ready to be watered again.

Mounties have a similar routine.

For my small, fairly tolerant collection, the process has worked well.

Nick, no doubt the speaker's successful with his method, even though it's counter-intuitive. Perhaps another testimony to orchids' adaptability.

I water differently depending on if the 'kids are inside or out. Over winter (or indoors 'kids) I water weekly/weakly using r/o water and flush with pure r/o @ every 4th watering. When outside, I use a hose end sprayer and water every 3-7 days with city water. Every 2 weeks I use a weak fertilizer solution from a watering can instead of the hose. So inside or out, never a flush right after using fert for me.

My mounties and mini-vanda types get misted/watered daily and fertilized a little less than everything else (a hassle to dip 'em and/or put fert in the pump sprayer, plus I'm lazy...) .

I struggle with some Masdies, I wonder if it's been too much fert? Hmmm.... something to try on one or two but I usually take the adage of they either adapt to my conditions/regimen or they end up Kev'ed.

Brooke, husband(s)? KY must be the opposite of Idaho ;-)

Bob

OK so I can't type particularly when in a hurry.

I admit I'm dense but I don't get the Idaho part. Help me out, I love a good joke.

Brooke

In Idaho there are Mormons with many wive(s)... The Sister Wives, etc...

Sorry...

Bob

Do you flush after each wife to prevent excessive fertilization?

Nick

Bob, I lived in Idaho Falls for a while. I understood you. Utah might be a better reference for the future! :)

Nick, Brigham Young apparently chose to not practice "birth control" using the flush method (or any other?). By the time of his death, Young had 56 children by 16 of his wives.

--Stitz--

And I thought rats and mice were prolific reproducers.

Nick

yeah rodents are prolific, by the litters!

Brigham was powered by the Grace of God!!

--Stitz--

I guess Joseph used lower octane gas, I mean grace, he only had 12 children with Emma, none of the rumored polygamous offspring passed the DNA test of modern time.

Nick

Looks like this thread got THE FLUSH!

What's right for Den. cuthbertsonii is wrong for just about all other orchids. I've never succeeded in keeping one. Could well be, as it comes from a region of very high rainfall, among other things, that it does like only very dilute fertilizer, but I sprinkle granular stuff on the rest of mine and often leave it on till it rains, can be several weeks. If you think about it most orchids get fertilized by bird splat once or twice a year and it is pretty potent stuff. I shouldn't worry about it.

Thanks for your input. As I said, I was surprised to hear this recommended by a reputable grower and was just running a poll to see if anyone does this.

For the first time ever, I'm keeping Dend cuthbersonii alive. Just barely. A few flowers and no die off. Certainly no robust growth. That being the case I'm willing to try any thing for these stubborn little buggers.

Nick

CONGRATS NICK!!

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Dend cuthbersonii are easy if you live in Pacifica. I have talked to many people in that general area and they all grow it well. Despite getting advice from so many people and trying my best to follow it, that plant is difficult to grow in SOCAL. I'm not the only one that has made that experience.

Nick

Nick,
Your problem is probably just the heat.
MAYBE setting up a sprinkling system that is pumped through an old freezer and that runs for most of the period that the temps are in excess of 80F might work.
The plants would have to be planted as mounts or in a media that will not break down so easily under these conditions.
This is the method that SBOE has used to cool off their cymbidiums in the summer though the water was not cooled
just tap water recycled through a sump and pump system.
For your purposes check out the link below for how to set up the chiller for the water. All I could add is to wrap the exposed pipes with insulation to keep the water cold to the point of delivery.
At the point of delivery you could set up irrigation with misters and drips and have your plants set up over a collection basin that is pumped back into the freezer.

Here is a link that might be useful: Make a homemade chiller

Finally met someone who relates to this. This lady grows species in SOCAL and starts off by watering (RO plus MSU fertilizer) her clean-water loving rain forest plants first. Then she waters everything else. When she's all done, she throws a valve which gives her clean RO water without the fertilizer and hoses off the rain forest plants only.

This is what I've been doing now.

Nick

You got some really great info on here and I have nothing to add to it other then the fact that when speakers come to meeting they are so informative and we learn so much. You can learn a lot from these growers, but no two do it the same way and beware!
When I first started out I took the advice of a speaker and almost lost all my plants. If what your doing is working don't change it. Your conditions are your conditions and tread the waters of change very carefully.

AMEN to "tread carefully" !! Hopefully, Nick is trying this "new" method on only a few plants at a time, and it could be because his method needs work !

Hard thing to learn but EVERY environment is different ! My "grows like a weed" is your "can't grow it at all" !

If it ain't broke, don't fix it !

It's not a question of fixing something that's broke. The plants are growing and blooming. Is that enough? No, nothing short of robust growth and spectacular bloom will suffice. A few month ago I did 3 things at the same time. I increased the amount of water each time, switched to MSU fertilizer and added a wetting agent. The growth of the cloud forest plants has indeed become nothing short of robust with new leaves busting out all over. Bulbos seemed not to care, they were growing before and they are still growing. the same way.

I'm only doing the flushing with the cloud forest plants. They are easy enough to monitor so I should be able to tell if there is a difference. Unless I notice a decrease in growth, I will continue this for some time, it makes sense. In nature they get fed sporadically but get flushed with pure rain water all the time.

They are all doing well except these d--- D cuthbersonii who still extend their middle finger to me. They are staying alive but the growth is anything but robust.

Nick

Nick,
How much light do you have them in?
Check out the very last line of the link below.

Here is a link that might be useful: Wolfgang H. Bandisch's observations of D. cuthbertsonii in the wild

I admire your dedication, and I think your logic is correct. I think we get too wrapped up in the fertilizer-fetish and forget that they make their own food with sunlight, water, and chlorophyll. We're just SUPPLEMENTING them with fertilizer and invito they get VERY little and VERY sporadic !

For 1 1/2 month now I have been flushing with pure RO water about 20 minutes after watering with RO + fertilizer water. Since there was robust growth on the cloud forest plants I was treating this way (only them) before and there is still robust growth now, the only conclusion one can reach this early is that it does not appear to do harm.

There were 4 plants that were not doing well, the infamous D cuthbersonii. Inspecting them today revealed new growth and new flower buds forming. They look more vigorous now than they ever have for me. For these finicky little buggers this method of watering seems to stimulate them. Since all of the others are also doing well, not necessarily better, I'll continue with this for a while.

Nick

"It's not a question of fixing something that's broke. The plants are growing and blooming. Is that enough? No, nothing short of robust growth and spectacular bloom will suffice."

Nick, very well stated!

BTW, a *prominent* mid-Atlantic orchidist grows his in reverse - this grower waits 'til after significant storms "flush" the orchid plants. THEN, the grower applies fertilizer solu(concoc)tions.

--Stitz--

Nick,

I'm wondering if it is just the double watering of the cloud forest plants that is helping? Might have been interesting to only fert 1 of the 'kids every 3/4 weeks and water heavily/double water with pure RO the other times?

I say this because I used to let some of my phrags sit in water, but lately I started to water them all heavily more often instead, 2-3 times a week. At least for me, the more frequent watering seems to help more than letting them stand in water and then watering heavily weekly. I divided a Barbara LeAnn x longifolium cross earlier this summer that I going try to use to experiment with both methods. I know how the sitting in water worked (just OK), so I'll try the fert/flush routine (fert/flush once weekly, water 3/4 times a week) on one and keep my current routine (fert weekly no flush, water 2-3 times/week) on the other. I'll report back when there's something to report. This plant has always had an issue of some browning leaf tips, this could be interesting to see if one of these methods may stop that from happening.

Fun stuff...

Bob

I live in LA, 550 miles north lives one of my sons with 2 grand children. San Francisco is 2/3 the way up. Once every two month the 'Pleurothallis Alliance' meets Sat midday in SF. I go to their meeting, then head north to spend the rest of the weekend with my family.

At their meeting I get to hear the opinions of some of the best cool growers in the US. Only one of them flushes after watering, most think of it as unnecessary. One comment was that this method duplicates what happens in nature as, at the beginning of a period of rain, the nutrients are brought to the plants initially, then the plants get flushed with nutrient free rain water.

I guess the only way to find out is to run a one year study which I am planning to set up one of these days. For nearly 2 month now I have had identical twin plants in SM vs redwood chips and for my type of watering, the redwood chips seem to work a little better. Need to do something similar with the flush concept.

There are 2 benches on either side of an aisle. Could flush one side only and set up a group of 'identical twins', one on each side, then compare their growth in a year. Since the light, air movement, even temperature is not exactly the same on each side one would have to flip them after a year and see if the findings hold on both sides of the isle. They should do something similar with the boneheads we have in congress.

Should be obvious that I'm retired with plenty of time on my hands. Love it!

Nick

3 months later and I see where the phrag that I fert and then flush 20 minutes later is not having nearly the issue with leaf tip burn as the one that doesn't get flushed after fert, but... the one that doesn't get flushed seems to be doing better overall, more robust growth and just a little stronger looking. It started off a little stronger when originally divided, so I can't say the flushing has anything to do with it being more robust.

I like the clean leaf tips and if the growth seems to keep up on both I'll probably do the flush thing for at least my phrags, (too big a PIA for all plants when they are inside for winter though...)

I'll report back again in a couple months..

Bob

I'm still doing it. The problem is that my plants were doing well before and they are doing well now. I cannot discern a difference. I have presented the method to several expert growers and found very little support. They believe it does neither harm nor good, none of them use anything like it. All of them periodically flush their plants with pure water without fertilizer, no argument there.

I have never before looked with this intensity for leaf tip burn and am considering stopping the practice on half of the greenhouse and observing if leaf tip damage appears in the next few month. I have one aisle so can easily double water one side, not the other. Since I mostly have one of each plant it is not a perfect test. The Dracs and Masdies are on each side of the aisle so some validity is there.

Nick