When to fertilize?

[jenn]

I have always fertilized after flushing my pots or mounts, but I have just heard to fertilize first, let the plant sit for 20 minutes, and then flush the pot, is better. I was wondering what you all do?

[LJA]

From my personal experience, if you fertilize a dry pot, you run a far greater risk of fertilizer burn on your plants' leaf tips. Did whoever say this also explain why it was better to fertilize and then flush with water? Because I've never heard that: if it really is better, I'd sure like to understand the reason!

[jenn]

A few folks from a different forum recommended this. What they say is based on information by Alan Kock from Gold Country Orchids, from the IPA2004. He stated (according to those few folks) that within the first 20 minutes a plants roots absorb all the nutrients and then can not absorb anything more. So, his suggestion is to fertilize first, then come back about 20 - 30 minutes later and water with plain water to help rid the salts.

This is interesting to me, but I am a little skeptical; sorry to say.

[LJA]

That's a little wierd: I know Allan; we met at last year's fall SWROGA and he's a member of our orchid society. He's *extremely* reputable and wouldn't give bad advice (or hasn't, that I've ever known). I just don't see him advocating throwing fertilizer on dry roots, but hell, maybe he is saying that. All I can say is, any time I've ever tried that here, the very next day practically I'd get tip or root burn, almost without fail.

Very strange. I'll have to email him and see what's up. Thanks for posting this Jenn; I just have a feeling there's something else to it and we're not getting the whole story.

[jenn]

I also have not had good experiences using fertilizer on dry roots, unless it's very, very diluted. I am curious to hear the whole story. Thank you.

[orchidaddict789]

Yes, me too. I find orchid roots to be more fragile than non-orchid plant roots. And I've burned several by fertilizing on dry roots (not orchids, though). This is interesting, so I wonder what's the whole story too.

[Rence]

They key to is fertilize your orchids on a weak solution ( weaker than on what is on the label) .

Some orchid growers fertilize their orchid 2-3 times a week , especially during growing season and little or no fertilizer during dormant period .

Here is an interesting tip: You need to keep the plant moist or water your orchid before fertilizing (to minimize root burn) then the following day, try to water the plant heavily in order to flush the excess salts and fertilizer. ( It is good if it rains since you won't water it anymore)

As for fertilizing your orchids and plants most growers recommend to fertilize them when it is sunny and you may delay your fertilization when there is over cast sky since plants cannot fully utilize the fertilizer into foods without proper lights and photosynthesis.

[LJA]

You need to keep the plant moist or water your orchid before fertilizing (to minimize root burn) then the following day, try to water the plant heavily in order to flush the excess salts and fertilizer. ( It is good if it rains since you won't water it anymore)

Rence, this is the part that's being called into question. Here we water with a very dilute solution on every watering, and as long as you use enough solution and flush it through the pot so that plenty comes out the drain holes, you don't need to use plain water for flushing. Excess salts will be washed out each time you fertilize.

The part that's mystifying to me about what Jenn heard is the claim that the plants won't take up nutrients after the first 20 minutes of being watered, and that we should therefore not use plain water first to moisten the roots, because (if I'm understanding this correctly) the water will use up some of that 20 minute time period, and the plant will absorb just water instead of nutrients.

My immediate question is, what about those plants--Phrags and Paphs--that need to be kept constantly damp, at least? What "first twenty minutes" are we talking about? Or, since this claim was allegedly made at the International Phalaenopsis Alliance conference, are we only talking about Phals? But most Phals, for optimum growth, shouldn't be allowed to completely dry out either, so again, what twenty minutes? If the plants are potted in a mud mix that retains moisture for at least a week under typical conditions, where does the 20 minute window come up in that week-long time span?

Just doesn't make any sense--at least, not to me. And if you water, as many growers do--with just plain water most of the time and only fertilize once a week or twice a month with a stronger solution, you run an even greater risk of burning by applying strong fertilizer on roots that have dried off.

So the whole claim is just a little bit weird to me, because if it's true, the whole theory behind Semi-Hydroponics--which works--would be thrown right out the window. There, nutrients are made *constantly available* to the plants, so there is no "twenty minutes after you fertilize." You're *always* fertilizing.

Very strange.

[LJA]

This is what he said regarding this issue in his reply:

...Always water fully prior to fertilizing. Almost all nutritional uptake is completed within 20 minutes, so if you are growing a salt sensitive plant like Dendrobium cuthbertsonii or Aeangis luteo-alba, I recommend that you flush the pots or mounts with plain water after 20 minutes to do away with the fertilizer salts.

So anyways, there you go. Makes quite a bit more sense, specifies what plants he was refering to, and follows along with all of our experience.

[Diane]

Maybe I'm just dense - or ??? But I don't pre-water my plants. They get watered once or twice a week (depending on type of plant), and I fertilize every watering with a weak fertilizer solution. So some of the roots are dry - like the Catts, while the Phals and Phrags will still be slightly moist. But I haven't burned any of my Catts. Soooo??? Is it because my mixture is so dilute?