Sometimes the best ideas come from the strangest thoughts.
So have you ever asked yourself ‘is urine good for hydrangeas?’.
Because that certainly is a strange thought.
But, let’s be honest, we each produce so much of the stuff, could it be used better than simply flushing it down the toilet?
Let’s find out…
Is Urine Good For Hydrangeas?
Human urine has been proven to be an excellent fertilizer for all kinds of vegetables and flowers, including hydrangeas. Urine is rich in nitrogen, potassium and phosphate, which are essential for the growth of any healthy plant. It must be diluted with around 10 to 15 parts water however otherwise it will burn any plant it comes into contact with.
It Contains the Same Ingredients as Fertilizer
Human urine contains almost exactly the same ingredients as a bag of fertilizer.
That in itself answers the question of whether urine is good for hydrangeas, or pretty much any other plant for that matter.
Next time you have a bag of fertilizer to hand, look at the list of ingredients.
You’ll see the word ‘urea’ for sure. Urine is 95% water, 2.5% urea and then a mixture of minerals, hormones, enzymes and salts.
It is also rich in nitrogen, phosphate and potassium, boasting an N-P-K ratio of 10:1:4.
In short, it is an excellent fertilizer for all kinds of plants.
It is Particularly Good for Plants That Suffer from Nitrogen Deficiency
One common issue with hydrangeas is the fact they can suffer from nitrogen deficiency.
Urine contains high levels of nitrogen and this makes it an excellent fertilizer for any nitrogen-loving plant.
Signs of nitrogen deficiency include leaves turning a yellow or pale green color.
It is also particularly effective for plants that consume a lot, so roses, tomatoes, potatoes and cucumbers all love it, as do hydrangeas, peonies, geraniums and petunias.
Another important substance that makes up urine is auxenotriolic acid or “auxin A”.
This is a growth regulating plant hormone, which promotes growth and root development.
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Studies Back Up Its Effectiveness
This isn’t just a new age fad, scientific studies have back up the effectiveness of urine as a fertilizer.
Dr. Philip Tierno, director of clinical microbiology and immunology at New York University Medical Center, New York City, said: “Urine is a good natural nitrogen-containing substance and probably could be easily utilized. There’s nothing wrong with using it.”
Håkan Jönsson, a researcher at the Swedish University of Agricultural Sciences, has been involved in the research of urine recycling for over two decades.
“The nutrients in urine are also in just the right form for plants to drink them up,” he said.
A group of environmental scientists at the University of Kuopio in Finland also put the substance to the test.
Surendra Pradhan and Helvi Heinonen-Tanski grew beets, cucumbers, tomatoes and cabbages as part of a study.
One plot was treated with mineral fertilizer, one with a mixture of urine and wood ash, one with just urine and one with no fertilizer.
After almost three months 280 beets were harvested.
The beetroots grown using urine and a mixture of urine and wood ash as fertilizer were found to be 10 percent and 27 percent larger by mass, respectively, than those grown in mineral fertilizer.
Full results of the study were published in the Journal of Agricultural and Food Chemistry, but the conclusion was clear: “Agricultural and health organizations should encourage people to use human urine as a fertilizer,” the paper said.
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It Has Additional Benefits
The phosphorous and potassium in urine is good at replenishing soil that has had such minerals depleted.
And apparently the scent of human urine (particularly male urine) might be useful in keeping animals away, due to the hormones it gives off.
You Must Dilute It
If you are going to use urine on your garden, it is extremely important you dilute it.
This is because undiluted urine is very high in nitrogen and, depending on the person, it can be very high in salts too.
Use it undiluted and it will most likely burn and kill any plant it comes into contact with.
It is recommended you dilute the urine with somewhere between 10 to 15 parts water.
Then simply sprinkle it onto the soil around your hydrangeas (or any other plant), not onto the plant itself.
If you plan on using it on potted plants, it needs to be weaker as they are more sensitive to fertilizer. Try a ratio of 30 to 50 parts water.
You shouldn’t use it every day either.
Even when diluted, applying excessive amounts of urine to your soil can lead to bushy, leafy plants and curled leaves.
But is it Safe?
Whilst it might sound slightly unpleasant, for the most part using urine to fertilize your plants is entirely safe.
The only times you should avoid it is if you are on medication or a smoker.
Let’s turn to Dr. Philip Tierno again to allay any fears you might have.
He has said there is little risk of contamination, as any pathogens in urine would be competing against microorganisms found in the soil.
They would “probably lose the battle. Urine is actually a relatively clean substance,” he said.
Does Urine Change The Color Of Hydrangeas?
In short, the answer is no.
The flower color of macrophyllas hydrangeas changes depending upon the soil pH:
- Soil pH of 5.5 or lower: blue flowers
- Soil pH of 5.5 to 6.5: purple flowers
- Soil pH of 6.5 or higher: pink flowers
It should be noted that white hydrangeas won’t change color based on soil pH.
But using urine as fertilizer, when diluted with water, will not have a substantial effect on the pH of soil.
The soil will buffer the effect the ammonia and urea content could have.
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Is Dog Pee Good For Hydrangeas?
The answer to this follows the same reasoning as the use of human urine.
However of course it is much harder to encourage a dog to pee in a container so you can dilute it with water!
If a dog pees on your hydrangea occasionally it won’t do it any harm.
But if a dog is going outside every morning and peeing in the same spot, the nitrogen content in its urine could likely result in the foliage getting burnt, turning brown and dying.
Furthermore, the root system could be damaged if the soil becomes saturated with nitrogen.
It is particularly likely to be a problem when a plant is young.
If this is a problem you really can’t stop, then watering the spot the dog pees will help dilute its urine.
Final Thoughts
So is urine good for hydrangeas?
Yes, it is more than good, it can be a fantastic fertilizer for them.
Its effectiveness as a fertilizer has been backed up by scientific studies as well.
It has a good balance of nitrogen, phosphate and potassium and will work wonders for any plant suffering from a nitrogen deficiency.
Just make sure you dilute it before sprinkling it on the soil.
On top of all of that, it is totally free.
The ABC News Technology and Science column estimated that in one year the average human could generate enough urine to fertilize 6,300 tomato plants.
That would be enough to produce 2.4 tons of tomatoes in one season.
Just think about that!