Urea

[Dess]

Hello again,

I think I'm addicted to this forum, hihihihi

I keep reading everywhere that you have to make sure that your fertilizer does not contain urea, because orchids hate that.
I just discovered that my high nitrogen fertilizer (30-10-10) does contain urea, and now I'm kind of scared because I used it a couple of times. Will it do considerable damage to the orchids? What are the consequences, what will it do to the orchids?

Dess

[Halloamey]

Hi Dess, what you read is right. Urea is potentially a very dangerous chemical for orchids only when you consider conventional growing. I fertilize my orchids with urea but only as a foliar spray at the rate of 75 ppm (75 mg/litre). Urea is bad when used at high doses (^200 ppm). Urea at 75 to 100 ppm is beneficial for orchids and most plants. One of my friends in the orchid industry tells me that it is a ingredient of the foilar spray they use on Phalaenopsis, which makes the plants grow and flower about 30% faster. Just avoid using it as the sole source of nitrogen.
If from the 300 mg nitrogen supplied by 1 gm of your fertilizer, 100 mg is (~30%) is from Urea then it should be just fine.
But urea is a strict NO if you are growing your orchids in Semi hydroponics or in a completely inorganic media.

[clintdawley]

I agree.

I've used plain old Urea-containing Miracle grow on my orchids at low concentrations with no detriment. Just mix it at half strength and you should be fine.

[Brutal_Dreamer]

I agree.

I've used plain old Urea-containing Miracle grow on my orchids at low concentrations with no detriment. Just mix it at half strength and you should be fine.

I also agree!!

Cheers,
BD

[BearWithMe]

This is so helpful! I have read many reports not to give urea. The rationale that I read states that urea requires the activity of soil bacteria to break down into a form that plants can use, and as epiphytes growing in nonsoil medium the orchids don't have the benefit of soil bacteria. On the other hand, most of the grow-type orchid foods that I have located contain urea. I suspected it wasn't that simple, and that the bacteria may be present in bark medium, but who knows? :-)

Anyway, it's good to see that others use the urea-containing fertilizers without harm and probably with benefit. I'll feel better about using it this year. I think I'll bet faster and better growth this way.

Thanks for this discussion even though it is old. It's very helpful!

[FrankP999]

Urea is cheaper to manufacture than other sources of nitrogen. That's one reason it is used in the large box "blue" powder ferts. Also, the type of nitrogen needed varies with the water hardness. From the Atlanta Orchid Society page at Resources

Because Atlanta’s water has low alkalinity, we should use a fertilizer that is high in nitrate as the nitrogen source and very low in ammonium and urea as the nitrogen source. But why? In water with low alkalinity, ammonium (NH4) and urea both drive the pH of the orchid mix down over time eventually to the point that low pH increases uptake of toxic metals, which lead to plant disease and eventually death if not corrected. Nitrate-based fertilizers add hydroxyl ions (OH-) and carbonate ions (HCO3) to the orchid mix. When used with water that has low alkalinity, the pH is not lowered over time.