Preferred fertilizer for orchids?

[notsogreenthumb]

I've seen lots of recommendations for a balanced fertilizer for organic media like bark chips, the theory being that you usually want a little extra Nitrogen, but the decomposing media creates that, so the balanced fertilizer results in something N heavy. Then I think during blooming, the most common is to switch to heavy phosphorous? Does that seem reasonable?

I have a Cattleya (Chyong Guu Swan 'Ruby Lip'), and a Oncidium Gilded Tower 'Mystic Maze' and a NoID Phal. Currently, the Phal is in sphagnum and the roots look decently happy through the pot, the Catt is in new bark chips and the Oncidium is unknown, but the top looks like a smooth coat of moss. It's the newest and still in bloom. I suspect the healthiest thing to do would be to cut the spike and repot, but I like the blooms, so I'll wait a bit to repot that one until the blooms are done.

I'm hoping that I can get one fertilizer to rule them all.

The guy that sold me the Catt last fall told me to use Osmocote slow release balanced, so I have that, but since I just changed out the media, I thought I'd get more opinions before I start fertilizing the new media.

Thanks in advance.

[notsogreenthumb]

During the wait for my thread to be approved, I found some posts about MSU fertilizer. That sounds like a winner.

[PaphMadMan]

MSU type formulas are a solid choice.

People can get almost politically irrational in orchid fertilizer discussions, not so much on this forum as in some others. You may hear some strong opinions. Here's what 42 years growing orchids plus a horticulture degree have taught me about fertilizing orchids. If you grow in organic media (based on bark, moss, coir, etc.) and you repot every couple years, and you aren't specializing in certain very salt-intolerant cloud forest orchids, and pick any decent water soluble fertilizer with micronutrients (it doesn't have to specifically for orchids), and use regularly but at no more than 1/4 the recommended strength/frequency on the container, it is extremely unlikely that fertilizer will ever be the thing that limits your success with orchids. And no fertilizer can make up for anything else that is lacking.

If you ever believe you have perfected every other aspect of orchid culture, then it may be time to take another look at fertilizer.

[ksriramkumar]

Sound advice from Kirk. I concur with his views. fertilizer discussions can be extremely flammable in other forums.

[notsogreenthumb]

Kirk and Sriram, great, thanks. Good info. I guess my concern is finding a "decent" fertilizer. I'm sure there are some fertilizers that advertise themselves as amazing fertilizers that are actually really poor.

I'm a member of an automotive forum. Advice that I'd give is to never go on to a serious auto forum and ask "what's the best oil for my car". I suspect it's similar to the fertilizer discussion.

[notsogreenthumb]

Wow, yeah, I found another thread with mentions of beer, ammonia, honey, worm tea, manure, etc....!

[PaphMadMan]

Kirk and Sriram, great, thanks. Good info. I guess my concern is finding a "decent" fertilizer. I'm sure there are some fertilizers that advertise themselves as amazing fertilizers that are actually really poor...

A few more specifics, as long as flame wars have not yet set in. It is best to avoid any fertilizer that must be hyped as "amazing" to get sales. As I said, the MSU type fertilizers are a solid decent choice, but there are many others. Note the difference between formulas for well water vs. rain water and be aware of your water quality. Calcium and magnesium can be the missing piece of the puzzle if you don't. Avoid urea as the primary nitrogen source. Make sure at least 4 or 5 micronutrients are listed.

For many years I used general purpose houseplant or African violet fertilizers that were cheap and locally available. Now I can afford fancy stuff and order from the internet. It all works. Ignore the hype. Read the fine print so you know what the fertilizer really contains. Alternate a couple formulas if you like, but avoid going down the bloom booster rabbit hole of seasonal this and that. Keep it simple and be consistent. Fertilizer is easy.

[notsogreenthumb]

Great, thanks again

[Traci]

I agree with everyone. I find a little goes a long way and I can't say that MSU was/is any better than the better gro that I use now. Because I use distilled water I supplement with CalMag but other than that I think any very dilute fertilizer is the best
Your analogy with the question about car oil is spot on

[raybark]

Being an engineer and bit of a nerd, I started delving into the nutritional needs of orchids, and it actually opened my eyes significantly. (Warning! Professorial mode: On)

If you look at the makeup of an orchid, it is 95% water. Of the remaining 5%, about 95% of that is carbon, oxygen, and nitrogen, with the first two coming from water and air; the N it gets from the fertilizer we apply. The remaining fraction of a percent is the rest of the stuff it gets from fertilizer.

Add to that some analyses of the water that drips down on orchids in the wild (their primary source of nutrition), and we see that it is almost devoid of any nutritional value - 15-25 ppm total dissolved solids (TDS) is typical, and that's only when it just starts raining - and we learn that most of that is nitrogen.

So my conclusion from that is that nitrogen is the most important nutrient, but it should be applied very sparingly, as 1) the plants have evolved to need very meager nutrition levels, and 2) excessive N can actually stifle flowering.

I won't go into details (look up "Rubisco" if you're a bit of an intellectual masochist), but in order for any plant to add about a pound of mass - a huge amount in orchids - it must absorb and process about 25 gallons (roughly 95 kg) of water, but only about 5 grams of nutrient elements.

So, about 7 or 8 years ago (I've been growing orchids for over 45 years now), all of that led me to this growing regimen:

• Use a VERY open potting medium, so the roots always have excellent air flow around them.
• Water the daylights out of them: Frequent & Flooding. Water is the driving force behind plant growth.
• Use a very small amount of fertilizer at every watering. I mean really little. Divide 2 by the %N on the labels to get the teaspoons per gallon to use.
• Make sure that "fertigation" solution contains nitrogen, calcium, and magnesium; the other stuff can "tag along". (Your water supply may have enough calcium and magnesium in it, but as a user of RO water, I add it.). I prefer K-Lite, a 12-1-1-10Ca-3Mg derivative of the MSU RO formula.

All of my plants seem very happy with that, and are growing and blooming better than I've ever seen - figures it would take me almost 40 years to figure that out....