ORCHID FEEDING CONTROVERSY! Oh my!! - Page 3 - Orchid Board

Ray · #21 06-03-2009, 11:11 AM

There are several issues to be addressed in Jonny's original post: The great growth/no flowers with Miracle-Gro is very likely simply due to the excessive nitrogen, but I'd bet that the insufficient growth with the Schultz stuff was not an issue with the formula at all.

I'll echo Steve's feeling that while you may be irrigating with lots of excess fertilizer, the retention is minimal - especially with the follow-up flushing - so what you have done is go from inadequate- to adequate feeding.

As to the "what concentration works or doesn't" part, we have to keep in mind that feeding needs to be looked at in terms of mass of nutrients absorbed, not in concentration applied (although that is one of the controls on that).

I don't think there is any such data for orchids (and they will vary all over the map, of course), but it is a very well established that takes 0.5g of nitrogen for a poinsettia cutting to mature to blooming over the chosen growing period. That is controlled by knowing:

how often the plants will be fed,
how much food they will get with that watering (i.e., the concentration), and
how much is retained in the medium and remains available.

There is a lot of science that goes into being a commercial nursery, so they design their media so that they know pretty exactly (through testing) what the nutrient retention is, and multiply that by the pot volumes to know the mass of the retained nitrogen in that pot. Then, by knowing that the plants will get watered "X" times a week for "Y" weeks, they can back-calculate from the target half a gram to determine the concentration of the fertilizer solution to be used.

Using my own situation as a comparative example, I feed at 125 ppm N at every watering, and water several times a week, and plants in S/H culture are constantly exposed to nutrients. On a very oversimplified "macro" level, if my pot retains 100g of solution, there is 12.5mg of N available to the plant. Compare that to a mounted plant, whose only "retention" is that absorbed in the velamen on the roots - maybe a milliliter total - so it's 100x less.

DelawareJim · #22 06-03-2009, 11:35 AM

Great description of commercial growing Ray. The trick is to get as much nutrient to the plant without reaching what the trade used to call "Luxury consumption". The point of diminishing returns where the growth and improved quality of the plant is less than the cost/value of the fertilizer being applied.

From a commercial grower perspective, I see wasted money. As a hobbyist, if it gives the result he wants and he's happy..... although I personally still see waste.

Cheers.
Jim

JonnyBravo · #23 06-03-2009, 12:42 PM

AHA! see, these are the kinds of replies i was looking for. i knew that it was probably the flushing away of the residue that was keeping my kids safe from burning, but i didn't think about the environmental dangers of all that fertilizer runoff. to that end, i will start cutting back my concentration as long as i'm getting the same results. but i do agree with the general consensus- it ain't broke, so i won't try to monkey with it too much. and i'm not growing tons of plants for commercial purposes, so i don't have to be too concerned about maximizing cost-efficiency while balancing perfect fertilizer retention in my media. buying a new little box of schultz or miracle-gro every 18 months or so is not a major concern to me. but i now understand waaayyy more than i did before. thanks guys! (any additional replies will still be welcomed, of course!)

shadytrake · #24 06-03-2009, 04:35 PM

I'm just getting my fertilizer "routine" going since building the SH/GH. I have found that early Saturday morning is the best time for me to get everyone watered then fed.

Of course the misting system and fans apply several times a day since it is now HOT here.

I have entered each plant into my computer journal with the suggested growing conditions (researched online) and have been tweeking their locations in the GH along with the specific blend of fertilizer.

For example I have read that the Epis require low N to avoid a retarded bloom development. So I have several different fertilizers depending on which group of chids gets each formulation.

Since I am building what I consider a hefty personal collection, I really don't want to waste $$ on over fertilizing. I would rather spend that money on another chid.

85% of my collection is in s/h so I found Ray's information very helpful. I was wondering if it was okay to leave the 1" reservoir with the fertilizer water or if I should flush it out. I guess it is okay then.

I am finding that I do measure out the fertilizer application based on the s/h pot size so I don't have too much waste run off.

I have heard from several people that you don't want to re-use the runoff fertilizer for your other chids, but I am thinking that I will let the runoff gather in a bucket and use it to fertilize my landscape plants. They should love it! They are hardy natives to this region so some weak orchid fertilizer will be dessert to them.

Becky15349 · #25 06-03-2009, 04:40 PM

Melissa, just a thought, usually people say its better to just water and fertilize at the same time, bc the roots can't take up fert if they are already full of water...I think I heard this from Gin, and it makes sense to me

shadytrake · #26 06-03-2009, 05:07 PM

Quote:

Originally Posted by Becky15349

Melissa, just a thought, usually people say its better to just water and fertilize at the same time, bc the roots can't take up fert if they are already full of water...I think I heard this from Gin, and it makes sense to me

So you don't flush first before you give the fertilizer?

isurus79 · #27 06-03-2009, 06:19 PM

Quote:

Originally Posted by shadytrake

So you don't flush first before you give the fertilizer?

I never do!

Ray · #28 06-03-2009, 10:00 PM

Shady,

If you are watering properly for semi-hydro culture - filling the pots rapidly to the top and letting it drain - then you are flushing at every watering.

As to the "wasting money on fertilizer" comment above, do a little math: Let's say you buy a quart of Dyna-Gro "Grow" formula (a good fertilizer) at today's list price of $19.00. At 7% N, if you feed at 125 ppm N, that quart will make up over 134 gallons of fertilizer, making each gallon cost a shade over $0.14.

Another example - the MSU Well Water formula I also carry - for the same concentration a $20 5# tub will make up 908 gallons at a mere $0.022 each - two cents!!!.

Your plants are relying on you. Don't be a cheap skate!

Jerry Delaney · #29 06-04-2009, 01:23 AM

Quote:

Your plants are relying on you. Don't be a cheap skate

I'm not cheap; I'm frugal!!! Cheap bad, frugal good!!! In our hot and dry Bakersfield, CA climate, I go through approximately 200 gallons of water every week in my greenhouses. If I punched the correct buttons on the calculator, that is 10,400 gallons each year and at $0.022/gallon. That adds up to ~$228.80 each year of which ~90% goes on the greenhouse floor. And, while I agree that is not necessarily a phenomenal amount of money, it's not exactly chicken feed either. That's the reason I currently am using a fertilizer that I can get for ~$1.00/lb delivered and am looking at some of the sustained release products currently on the market. I certainly agree with the rest of your statements though, Ray!

shadytrake · #30 06-04-2009, 02:42 AM

Quote:

Originally Posted by Ray

Shady,
Your plants are relying on you. Don't be a cheap skate!

I didn't say wasting money on fertilizer, I said wasting money on OVER fertilizing.

In other words, I was saying that I am carefully measuring so that I am using the right amounts of fertilizer and not just throwing extra on the floor.