rec.gardens.orchids #10345
From: ahicks@nmt.edu (Aaron Hicks)
Subject: Re: Fertilizing question
Date: Tue Sep 03 21:40:03 MDT 1996
Organization: New Mexico Institute of Mining and Technology
Lines: 105

        Kevin (kegriff@ix.netcom.com) shares a common thread regarding
terminal bewilderment with respect to fertilizer.
        This being an election year, fertilizer is once more in profusion
(please note this year they are making _promises_ regarding taxes, so
they must be serious); I have decided to enter the ensuing ruckus, capital
letters be damned in English and Latin alike, with the following obfusction:

>I am a bit confused as to which fertilizers to use and when.  I
>currently have a collection of about 15 phaelanopsis and 15 assorted
>other species of orchids; oncidium, vanda, vuyl, brassidium, dendrobium,
>angraecum, and others.  I used 20-20-20 on all those plants which were
>developing new growth and, approximately, a 18-36-24, for those plants
>which are in the process of producing influorences.  Throughout the
>summer, I fed most of the orchid about a 1/4 to 1/2 concentration of
>fertilizer every two weeks.
>
>Could anyone tell me if this is how I should be feeding my plants or
>should I consider another method?  I have not observed any problems

        First off: you're not going to kill a plant from an element
deficiency. Well, it's _possible_, but unlikely. If you bump the pH up
too high, you might get chlorosis from the iron getting locked up, but
unless you're hosing your plants down with triple distilled water, it's
not likely to happen (hate mail with respect to these comments to:
ahicks@nmt.edu  Thank you in advance).

        Second off: miracle fertilizers aren't. And, no, I am not directing
this towards Miracle Grow, as this is what I use. I once posted on the OLD
that I've never found anything that grows orchids fastern' crabgrass, or
that could grow redwoods on a bowling ball: I got a few accolades via
e-mail for that one, as many feel the same. Some people love certain
fertilizers or nutrient formulations; some just don't care, so long as it's
the same stuff every month. Some rotate fertilizers, so that it's not possible
to get a "true" deficiency.

        Third: number three has been recalled by the Consumer Product
Safety Commission.

        Four: Lather. Rinse. Repeat. Sound familiar? These are the three
finest words ever invented by marketers. How else could one develop a single
phrase that is comprised of only 5 syllables, yet doubles the use of your
product? WOW!
        Much is the same with orchid fertilizer. Orchids just don't _need_
gobs and gobs of nutrients, with the exception of a few VERY large species
when they are in full growth, like grammatophyllums, "standard" cymbidiums,
and so forth. I have to concede that if my diet was normally bird droppings
and tree bark (given the choice of these two, I'd probably go for the tree
bark), a change of pace to Really Fast Gro (R) brand fertilizer would
probably seem pretty keen.
        All the same, one certainly doesn't need to dose fertilizer as strong
as it says on the package. 1/4 to 1/2 strength sounds pretty good; my *very*
general rule sez that plants with smaller roots get weaker stuff, and
plants with larger roots can take higher concentrations. Plants with hairy
roots (Phrags, Paphs, etc.) should get even less. The reason is pretty simple:
surface area to mass ratios are larger in smaller roots; smaller values
means that the roots are easier to burn. Cinch: these plants need dilute
solutions relative to other plants.

        Five: A lot of it depends upon your water quality, how often you water,
clay versus plastic pots...
        Ye gods! Y'all never figured orchid nutrition would be that wacky,
did you? It all comes down to one factor: osmosis (see the last paragraph
of number 4). If your water is hard, it already has lots of dissolved salts.
If you add *more* with fertilizer, you're sucking more water out of the
plant as the media goes dry. Plus, as the media goes dry, it precipitates
out these salts (primarily calcium, magnesium, sodium and potassium cations,
combined with carbonate, sulphate, chloride and fluoride anions to form salts)
which complicate the problem each time you water.
        Lesson learned: the harder the water, the more you fertilize, the
more water you lose out of the media between waterings, the more often you
should flush your pots. What does flushing consist of? Water. HARD. Water
so hard that the water runs out of the bottom of the pot, dislodging mineral
crusts and washing out concentrated solutions left over from previous
waterings. If possible, do it a few days after you have watered so that
the media is still moist.
        One last tip: the best time to fertilize is a few days after the
last time you watered. In other words, you could water on a Monday, followed
by a fertilizer boost on Wednesday. This serves two purposes:
        1) The media is already moist, so it takes up the fertilizer solution
with no problems (the surface tension is already broken).
        2) Roots suffer less osmotic "shock" going from dry to surrounded
by a solution of fertilizer. And, well- this may be a crock, and I admit it;
I have nothing to back up this one. :-P Makes sense, but then again, so
did that whole "Earth as the Center of the Universe" thing several hundred
years ago.
        Also, you end up using less fertilizer; it soaks in fast, so less
drops out of the bottom of the pot before it starts to soak in.


        Summary:
        1) Doesn't matter what you use; take it easy on the fertilizers
that use urea as its nitrogen source.
        2) Don't fertilize sick plants, or plants that are not actively
growing.
        3) How MUCH you use depends upon what kind of plants you're growing,
the time of year, your growing conditions, the phase of the moon, how long
your hair is, and probably your brand of aftershave.


        Awaiting a visit from the Miracle Grow man (and the ensuing
controversy),

        -AJHicks
        Wonk
        Socorro, NM