Urea vs. non-urea fertilizers?

Sarasota, FL(Zone 9b)

A question has been raised on another thread "Is this sunburn?" about the veracity of the popular belief that you "must" fertilize orchids only with non-urea based fertilizers.

Please weigh in with your opinions, how you fertilize and what you use. If you know anyone who might actually be an authority, or know of a documented study that has been done, is there a link to it/them?

Inquiring minds want to know if this is just a long- and widely-held belief or a scientifically documented fact.

Thanks Elaine

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Odessa, FL(Zone 9b)

All of the orchid classes I have taken, all of the lectures I have heard at society meetings and all of the reading I have done on the AOS web site call for non urea fertilizers. I didn't know that piece of knowledge was controversial. What I do that is controversial is mist with a weak fertilizer solution every day. I don't know many folks that would give me a thumbs up on that practice but my orchids seem to be happy. I think orchids want to live and are good at adapting to reasonable conditions. The bottom line is do what works for you and your plants.


Sarasota, FL(Zone 9b)

I know, I've taken it as common knowledge, too. I was surprised the culture sheets I read on the AOS site today did NOT specify non-urea fert. I read the fertilizing sections for 8 or 9 of the orchid varieties, and not one of them mentioned any specific type of fertilizer, other than various N-P-K ratios for each different type. The novice sheets for 3 varieties did specify "orchid fertilizer". Ted did a good search and found some references supporting non-urea fert on the AOS site. He's been growing his using regular fert for 5 years! That tells me it can't be all that bad.

My excellent book "Orchids to Know and Grow" doesn't say a word (that I've found so far) about non-urea based ferts either. This is what got my curiosity piqued today. I'm going to fall asleep over that book tonight, I can tell. The two authors both seem to have great creds.

Daily misting with weak fert WAS mentioned somewhere, I forget where I saw it now. This was a recommended practice for climates with high heat and humidity conditions. Here we are! I've been doing that too, in the warm weather at least. In winter I mist with plain water every second day. Just about every one of my orchids are showing nice healthy new growth, so it's working.

Brea, CA(Zone 10b)

Growmore products contain both types of Nitrogen, so I guess I'm safe. lol

SF Bay Area, CA(Zone 9b)

As a data point, I was at Lowe's today and noticed that Miracle-Gro 30-10-10 Orchid fertilizer has 26% urea nitrogen, 4% ammoniacal nitrogen.

Sarasota, FL(Zone 9b)

Wow, that is outrageous. Hope you didn't buy it! Just checked the regular Miracle Gro 24 - 8 - 16 package and it has 3.5% ammoniacal and 20.5% urea nitrate. Almost the same ratio as the Orchid formula.

My Better-Gro "Orchid Plus" 20-14-13 has no urea nitrogen. 11% nitrate nitrogen, and 9% ammoniacal nitrogen.

Brea, CA(Zone 10b)

Actually, the Gromore has no urea nitrogen. Just nitrate and ammoniacal

SF Bay Area, CA(Zone 9b)

Just so everyone's on the same page, the reason this came up is because I had read this thread on gardenweb: http://forums2.gardenweb.com/forums/load/orchids/msg032222191547.html

The bottom line of which eventually was: "The source of nitrogen I think is not of great importance compared to making sure the fertilizer you use has all the micronutrients plus calcium and magnesium. The purpose of my original post was that someone should not worry about whether the fertilizer they use has urea or not."

BTW, I looked at 3-4 different orchid fertilizers today and none of them had calcium.

This message was edited Jun 16, 2012 7:37 PM

Sarasota, FL(Zone 9b)

Geg, I think that article is highly suspect. The writer's references, including the "initial study" done in Germany are not related to orchids. He's no expert and he "thinks" that the research done on crop plants can be applied to orchids. They're epiphytes so they definitely take up nutrients in a different way to crop plants.

An article, and a section in a book I read today (both written by people with degrees in hort and botany), said "urea-based nitrogen requires the action of soil-borne bacteria to become available to plants". Neither gives a source study or data to support this claim, though. But if this is the case, and you're growing orchids without soil as most of us do, they can't get the nitrogen from the urea.

My orchids get a shot of calcium if I spray them down with the hose, as my irrigation water is untreated well water. I don't see any calcium on the labels of any of my fertilizers either. Here's an interesting article by a PhD. that might explain some of our questions:

This message was edited Jun 16, 2012 11:41 PM

SF Bay Area, CA(Zone 9b)

My tap water only has ~44 ppm calcium :(

Sarasota, FL(Zone 9b)

Don't feel bad, that SF tap water is the most wonderful drinking water I've ever tasted. There's a calcium product used to cure blossom-end rot on tomatoes that you could use to supplement a little calcium for your orchids. I forget the name.

Anyway, today's news is, I got a reply e-mail from Tom Sheehan, co-author of my "Orchids to Know and Grow" book, and professor emeritus in environmental Hort at UF. Since he says he's been growing orchids for 70+ years, he must be getting on, but still vastly experienced, and also somewhat qualified. Still he just muddied the water some more. Here's what he said:

"Elaine, Glad to hear that the orchid bug has bitten you and unfortunately there is no cure and one just continues to expand one’s collection ad- infinitum. Good luck with yours.

With regards to your orchid fertilizer question, I have seen the same information on urea printed in a number of orchid books, yet am not aware of any definitive work in this area. In all my 70+ years of growing orchids I have found that orchid fertilization is the most controversial part of orchid culture with each grower having his own special fertilizer or fertilizer program. Since orchids grow in a wide variety of media, it is difficult to come up with a specific fertilizer for all orchids. I have always been of the opinion that any balanced (NPK) fertilizer used as recommended on the container is usually adequate for the majority of the orchids grown today. As a matter of fact, my present fertilizer program in my greenhouse consists of bi-weekly application of Miracle Grow, using their proportioner. I always irrigate the next day to wash the excess nutrients off of the leaves to prevent green algae from growing on the foliage. Basically, I am folia fertilizing my orchids and they do very well."

So, our GreenEyedGuru, I take it back. Go ahead and finish using up your regular Miracle Gro if you haven't already bought orchid fert. As Jim pointed out, you've got to go with what works for you, and orchids are generally pretty tough so they will often adapt anyway.

Me, I might try Tom Sheehan's method for a couple of months and see what happens here. Now, where the heck is that hose-end proportioner I had . . . ?

Odessa, FL(Zone 9b)

Elaine, I think you are thinking of Dolomite.


Sarasota, FL(Zone 9b)

Dolomite would work to supply calcium, but it would be really messy and difficult to use, don't you think? The product I'm thinking of is a liquid with the calcium somehow in suspension or dissolved. You use it as a douse on plants that have blossom-end rot and it stops like magic.

I never have the problem any more because I grow my tomatoes in Earth Boxes and they supply Dolomite to mix in when you fill up the box. So it's been years since I last bought the stuff I'm thinking of.

Now it's going to bug me, just when my mind was slowing down off the buzz about urea . . . I'm going over to the Tomato Forum to ask some of those folks what it is.

Sarasota, FL(Zone 9b)

The calcium treatment I was thinking of is a spray called "Enz-Rot".

You could probably put a little bit in with your orchid fertilizer to supplement calcium.

I'd keep a good eye out for deposits if you use it. My well water leaves white droplet deposits on the orchid leaves. If I don't rinse regularly with rainwater, (or if it doesn't rain) they get pretty scruffy looking.

Sarasota, FL(Zone 9b)

To recap the fertilizer question, just for your interest:

I had two Lc. Jungle Eyes which is a mini, and two Pot. Toshie Aoki 'Pizazz' crosses. I separated one of each, and have been fertilizing them with regular old Miracle Gro for the last two months. Otherwise, they've all four had the same treatment, same water, same light. They've even been in the same candle holders.

Here are the pics I took in June of the four little lab rats

Thumbnail by dyzzypyxxy Thumbnail by dyzzypyxxy
Sarasota, FL(Zone 9b)

Here are the same four little plants, pictures taken just now. The two on the right have been getting Miracle Gro, the other two have had non-urea orchid fertilizer. I did my best to mix the formula so the N concentrations were about the same.

Three of the four have healthy new spikes coming along. The big difference I see is the color of the leaves, the Miracle Gro ones are darker green. The plants have been growing side by side in the same light situation.

Don't know about you all, but this satisfies me the theory that orchids need non-urea fertilizer might not hold water. Looks like the urea-based fert worked just fine.

Thumbnail by dyzzypyxxy
Odessa, FL(Zone 9b)

Interesting but I keep thinking of other factors that may come into play.


Sarasota, FL(Zone 9b)

So right, Jim. My orchids are all outdoors - exposed to more natural influences including bacteria, algae, fungus, bugs etc. than those growing indoors or in a greenhouse.

Plus, the plants may have grown the same way with no fertilizer at all, but what they get from the rain. Too bad I didn't have a third pair of these little guys to act as a "control" with no fert.

I'm going to continue the comparison, and will report again in October. It's not exactly a scientific study I'm conducting here, just trying to satisfy my own curiosity, really. I had the two pairs of orchids, and the two kinds of fert so when the question popped up, why not?

Brea, CA(Zone 10b)

Thanx for the update. Interesting to say the least

Ann Arbor, MI

Interesting stuff. Elaine, If you continue with your experiment, could you please let us know how things go? I've wondered about this one myself.

Sarasota, FL(Zone 9b)

No worries, the experiment continues as long as I have the continuing supply of materials . ... Miracle-Gro, the other orchid fert, and two pairs of little guinea pig orchids. As I said, not exactly scientific, but it's fun and will be nice if it satisfies my curiosity.

One of the little orchids lost a couple of leaves two days ago, but seems to be perking up again now. Heavy dose of cinnamon did the trick, I hope.

Sarasota, FL(Zone 9b)

UPdate on my fertilizer comparison test. One pair of my test subjects has gone, I gave away one plant of the Lc. Jungle Eyes and the other died . (don't worry Mj, I have another)

So my two little Pot. Fire Fantasy X Toshie Aoki 'Pizazz' are the remaining test subjects. Plant on the left has been fertilized with plain ol' Miracle Gro and the other with Better Gro Orchid formula (non-urea, all nitrogen from Nitrates). Both get sprayed every day or two (if it doesn't rain) with a weak solution of the fert, - about 1/4 strength recommended on the package, plus a few drops of Superthrive in each sprayer mixed in rain water from my rain barrels. They are always side by side in the same area of the garden, or in the pool cage. Both are in the same size pots and were re-potted at the same time. Bark mix in both the pots as medium.

An important factor here is that all my orchids are growing outdoors under or near the leaf canopy of a huge old oak tree. So the conditions are not as controlled as a greenhouse would be. They all get what might be termed "outside influences" which include natural rain water, dew that drips off the oak leaves, dirt that falls from the oak tree, insects, fungus and everything else that floats around in the air. My garden is mostly chemical-free - unless you count soapy water spray I use on my veggies and brugmansias to keep he spider mites at bay.

At this point, I honestly can't see a difference. Neither has put up a spike, but both have new leaves from the summer, and each has a new pb coming along. Leaves are relatively the same size and color. Your opinions welcome!

The experiment will continue, although I do change the routine a bit in winter. I reduce fertilizer application to every second misting during cool weather as the plants slow down their growth. Still, these two little plants will get equal treatment with the two different solutions and I will report back in another couple of months.


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