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Fertilising geraniums with homemade preparations? Why experts advise against it

Fertilizing geraniums with home remedies sounds easy, but it's risky. In this article, we reveal why experts advise against home remedies and how to fertilize your geraniums optimally.

Fertilise your geraniums with homemade fertilisers!” Have you ever heard this advice in a gardening forum? In this article, we explain why the experts at meine-geranien.de advise against this practice and which methods really lead to healthy geraniums that bloom all summer long. 

Overview: Why homemade fertilisers are not recommended for fertilising geraniums

  • Geraniums are hungry eaters. They need a lot of nutrients to grow healthy leaves and bloom profusely.   
  • Homemade fertilisers don’t necessarily contain the right amount of the necessary nutrients.  
  • Using them can lead to malnutrition and problems with the soil. It can also encourage pests and fungal diseases.  

What experts advise instead:

  • Special geranium or flowering plant fertiliser contains all the nutrients geraniums need in optimal proportions.  
  • It promotes healthy growth and abundant flowering and ensures healthy and beautiful balcony planting.  
  • Liquid fertilisers are simple to use and easy to dose. Membrane-coated slow-release fertilisers provide the plants with nutrients throughout the summer. 

 

The fact is, homemade fertilisers don't deliver what they promise

When it comes to fertilising geraniums, advice books often suggest using simple homemade fertilisers such as milk, egg or banana peel. Even clipped toenails and urine are sometimes recommended as fertilisers. What a colourful mixture!  

  

We’ll see what’s behind it in a moment. First of all, we don’t know of a single common homemade fertilisers we can recommend with a clear conscience if your goal is to see your geraniums grow vigorously and enjoy the sight of lush flowers on your balcony all summer long. Well meant is not always well done. Here we go. 

If you fertilise geraniums with liquid fertiliser using homemade preparations from your kitchen, you risk infections from fungi and bacteria. It's better to drink milk, beer and cola yourself.

Milk brings nutrients into your window box, but also carbohydrates and fats. Both are substances that can cause plant-damaging fungi and bacteria to proliferate. So instead of lush flowers, you risk diseases if you fertilise your geraniums with milk. What’s more, it will never meet the needs of your nutrient-hungry geraniums. Let’s tell it like it is: geraniums are not calves.  

Even stale beer and the water you cooked your food in don’t provide enough power to enrich the small volume of soil in boxes and containers with enough plant food. Worse still, the by-products carried along feed the bad fungi and bacteria.   

Even cola is not suitable as a phosphorus fertiliser, despite the phosphoric acid it contains. Using cola as a fertiliser will turn the soil so acidic over time that the geraniums will no longer grow properly.   

We also believe that it is ethically unsound to use food as a fertiliser. 

Vegetable waste from the kitchen is better placed on the compost heap or in a wormery, as geraniums cannot directly utilise the nutrients it contains.

Banana peels provide potassium, phosphorus and magnesium, all substances geraniums would lick their lips for if they had any! There’s just one problem: it’s not as if you can put the peel – fresh, dried or cut into small pieces – onto the soil and the geraniums will just help themselves to it. If you put banana peel between your geraniums, you’ll attract pests at best. 

A banana peel still needs to be turned into natural fertiliser.

In fact, it works like this: firstly, worms, insects and micro-organisms have to get to work and break down the banana peel in countless steps into such small particles that the geranium roots can absorb them.  

  

This process is called mineralisation and it is exactly what it sounds like: a lot of work. An army of creatures has to work for weeks to turn the organic substance “banana peel” back into plant-available minerals and nutrient salts. 

Geranium roots have no teeth.

It makes even less sense to scatter crushed eggshells over the soil in a window box. Even in a bioactive compost, it takes years for them to be broken down by soil organisms so the plants can benefit. Not to mention the fact that eggshells consist almost entirely of calcium.  

Yes, calcium is one of the vital plant nutrients, but in excess it shifts the pH value of the soil into an unfavourable range for geraniums. That would be the end of colourful flowers and vibrant green foliage. 

Pet waste as a fertiliser is not suitable for balconies and patios.

Without processing, even small animal manure is not suitable as fertiliser. Animal faeces such as rabbit droppings or chicken manure stink. They can contain salmonella and pathogenic bacteria and attract flies, maggots and other creatures. Not to mention that it’s impossible to mix the manure into the soil of a densely covered balcony box without damaging your geraniums. 

Aquarium owners might have a better chance if it weren't for...

Things might work a little better with water from a freshwater aquarium. Guppies, catfish and the like do indeed produce a liquid solution with their faeces that contains plenty of nutrients. However, the exact amount is only known after a laboratory analysis.  

If you are interested in systems that use waste water from fish farms as fertiliser for crops, take a look at the Rennsteig Tropical House, in Upper Franconia, Germany. There, piranhas fertilise certified organic tropical fruits such as papayas, passion fruit and guavas! The operators have set up an under-glass polyculture system with an almost closed cycle in which water, energy and biomass are utilised multiple times. The fruits produced are of such high quality that they regularly end up on the plates of two-Michelin-star German chef Tobias Bätz. The effort required to optimally feed plants with water from the aquarium is immense. We believe that you have other hobbies than fertilising geraniums. That’s why we don’t recommend this method. 

Don't change your personal hygiene routine. Please continue to throw hair and fingernail and toenail clippings in the organic waste, not in the geranium box.

The idea of using hair and nails as fertiliser for geraniums is actually a clever one. In principle, the horn shavings you can buy as organic slow-release fertiliser are no different. Horn shavings are the crushed horns and hooves of animals.   

Like horns and hooves, your hair and nails are rich in keratin, a fibrous protein found in the outer layer of mammalian skin. Keratin consists of long chains of amino acids and nitrogen is the key element in its structure. This is why horn shavings work as a fertiliser.   

But just as with kitchen waste, soil organisms first have to work to turn the nitrogen in keratin into nitrogen that plants can use. This takes time, because the microbes have a long time to nibble on horns, hooves, hair and nails.   

This is why horn shavings are almost exclusively used to fertilise garden beds, where you can keep an eye on the nutrient supply in the long term. In contrast, a balcony summer with geraniums is a real sprint!  

Soup bones contain a lot of collagen. This is also a protein. And plants cannot absorb this protein directly either. Not even if the bones are ground into a fine powder. 

Urine as a fertiliser? Geraniums can do without human urea applications.

Fertilising geraniums or other plants with your own urine seems interesting at first glance because urine contains nitrogen, which is an important nutrient for plants. But let’s be honest: who wants to do their business in the geraniums?  

Apart from such cultural reasons, there are other reasons why it’s not advisable to fertilise geraniums with urine: In addition to nitrogen, human pee also contains salts. These can accumulate in the container and damage the plants. Urine also lacks the other nutrients that flowering plants, such as geraniums, also need to grow. Nitrogenous faeces alone will certainly not produce a magnificent sea of flowers.  

And this is where the microbes come into play again: the nitrogen in urine is mainly present as urea. Before your geraniums can utilise it, it must be converted into nitrate. This happens in three steps. 

Urine as a fertiliser? Geraniums can do without human urea applications.

Fertilising geraniums or other plants with your own urine seems interesting at first glance because urine contains nitrogen, which is an important nutrient for plants. But let’s be honest: who wants to do their business in the geraniums?  

Apart from such cultural reasons, there are other reasons why it’s not advisable to fertilise geraniums with urine: In addition to nitrogen, human pee also contains salts. These can accumulate in the container and damage the plants. Urine also lacks the other nutrients that flowering plants, such as geraniums, also need to grow. Nitrogenous faeces alone will certainly not produce a magnificent sea of flowers.  

And this is where the microbes come into play again: the nitrogen in urine is mainly present as urea. Before your geraniums can utilise it, it must be converted into nitrate. This happens in three steps. 

An excursion into biochemistry: nitrification

First, bacteria in the soil that possess the enzyme urease convert the urea to ammonium. Then new little helpers come into play. They are called nitrosomonas and use the enzymes ammonium mono-oxygenase (AMO) and hydroxylamine oxidoreductase (HAO) to oxidise ammonium to nitrite. Only in the third step does urea become nitrate, namely when nitrobacter oxidise nitrite to nitrate with the enzyme nitro-oxidoreductase (NOR).  

All this magic works best at a pH value of 7 to 8, which is sub-optimal for geraniums. The best pH for them is around pH 6.  

Urine alone as a fertiliser is not enough. And if things go badly, the urea is washed out of the soil before the plants can use it. That’s just daft! 

Knowledge at a glance:

6 reasons why experts advise against fertilising geraniums with homemade fertiliser

  1. Risk of pests and diseases 

Organic materials such as banana peels can attract pests and promote diseases.   

 

  1. Imbalances in the nutrient content 

Although homemade fertilisers such as milk, eggshells or urine contain important nutrients, they do not contain the right amount and mixture that geraniums need.  

 

  1. Unpredictable effect 

The effect of homemade fertilisers is often unpredictable and can depend on the quality of the raw materials used and the environmental conditions.  

 

  1. Deterioration of the soil 

Many homemade fetilisers can deteriorate the soil, which can damage the roots.  

 

  1. Odour nuisance 

Homemade fertilisers, such as fish water or rabbit manure, can cause unpleasant odours.  

 

  1. Effort 

The preparation and application of homemade fertilisers is considerably more time-consuming than the use of commercial products, and with poorer results. 

What geraniums really need: Tips for proper care

Geraniums are hardy and easy to care for. They need lots of nutrients to produce plenty of flowers.  

  

Professional gardeners swear by a ratio of the most important nutrients nitrogen, phosphorus, potassium and magnesium of 4:2:6:3. The pH value of the soil in which you plant these balcony plants should ideally be around 6.0.  

Geraniums grow best in a location in full sun or light, partial shade. They should be watered regularly without waterlogging. Wilted flowers should be removed regularly. 

How to easily fertilise geraniums as required

You can get the nutrient supply under control with quality fertiliser from specialist garden retailers. Geranium or flowering plant fertilisers contain everything your geraniums need in an optimal ratio.   

  

Liquid fertilisers are easy to dose. With membrane-coated slow-release fertilisers, you can add a nutrient store to the soil as soon as you plant. This ensures your plants are ideally nourished for almost the entire summer.  

  

Do you want to fertilise sustainably and not use artificial products? Then ask a trusted gardener about natural flowering plant fertilisers that will safely feed your balcony plants. Experts also call this organic or biological fertiliser. 

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