Usually, it is the fertilizer that makes a difference between just a good orchid and an eye-catching specimen plant. In order to thrive, orchids like any other plant need fertilizer. Well-fertilized orchids are healthier, i.e. they bear more flowers and hold their leaves for a long time. However, over the counter fertilizers contain chemicals as well as other unnatural ingredients that are not always the most ideal way of fertilizing orchid plants. Fortunately, unique versions of natural fertilizer secrets have been concocted by many gardeners and the results after using these fertilizers have been amazing. Moreover, since most orchid plants are grown in pots with tree bark, the bark absorbs much of the important nutrients instead of the roots of the orchid. This can be overcome with the help of the following alternatives.
It is true that orchids require less fertilizer than most other plants. However, since orchids grow best in low-bark, low-nutrient mixes, administer some of the following natural fertilizers can be beneficial.
Please Note: I have incorporated some additional commentary in this article and to distinguish commentary from original text, I am using an italicised font.
Eggshells
Eggshells are a great source of calcium and potassium, which are nutrients orchids thrive on. A mortar can be used to crush eggshells, which can be sprinkled on orchid bark. This way, the crushed eggshells will not wash away during water. Instead of directly sprinkling the crushed eggshells, the crushed eggshells can also be boiled up in a large pot of water. The heat should be turned off after the water has reached watering[sic] (boiling) point and the eggshells should be allowed to steep for at least eight hours. The shells can then be discarded, and the water can be poured into a spray bottle for convenient use. This nutrient-rich natural orchid fertilizer can be spray around the orchids onto the bark.
If you have a modern food processor or blender, consider the idea of pulverizing eggshells to a powder. This poweder can be shaken onto bark like a salt shaker. Use caution, and apply sparingly. Too much of a good thing can be a bad thing.
The idea of boiling eggsells in water is also worth a try except the author makes no mention of how many cracked eggshells or how much water. If I was to try this, I would use a dozen eggs, and before using the water, cut it by a quarter. This water could be used as a mist on the orchids, or poured onto the medium as if watering. I would recommend watering the orchid first to prevent "shock and burn".
Epsom salt
Magnesium can be provided to orchids using Epsom salt. Healthier growth as well as stronger roots is promoted this way. One teaspoon of Epsom salt can be mixed with water and then be used as part of regular fertilizing.
This is from the AOS web site regarding Epsom salt (magnesium):
I have recently learned that Epsom salts work well for getting phalaenopsis to bloom. My questions are: Does this work for all orchids? If not, which ones should get it, which ones definitely should not get it? How often do I apply Epsom salts? I've read everything from monthly to twice a year. How much do I apply? What does the Epsom salts do? Is magnesium not sufficiently present in fertilizer? So why is the boost from salts particularly important? — Tania Self
You will not read much on this topic in regard to orchids for there has been little research done. As so often is the case, the myths and misinformation get spread widely, often by people selling something. However, this much is true: Magnesium is an essential element in orchid nutrition. In Europe, fertilizer formulas are often expressed as N-P-K-Mg, indicating that it is considered as a macroelement rather than a micronutrient. It can be made available to orchids in many forms. Potting mixes will often contain dolomitic lime for a slow-release source. Growers either top-dress with magnesium sulphate in the spring or they apply it dissolved in water in the autumn as a stand-alone application at 1tbs per gallon. Sophisticated growers will usually add magnesium in a chelated form to their liquid-fertilizer solutions. Plant need can be gauged by tissue analysis but this is probably more complex than most hobby growers can be bothered with.
Magnesium is critical to the flower-initiation process in orchids. Instances of disappointing flower production in Cymbidium, for example, have been linked to low levels of magnesium in plant tissue. The recent work with Phalaenopsis you have read supports previous studies on Cymbidium and it is reasonable to presume that magnesium is a macroelement for most orchid genera. — Andy Easton
Milk or Buttermilk
Both milk and buttermilk are rich sources of nitrogen due to their protein content. In addition, they are easy to find and use products since they are used in homes on a daily basis. Instead of actually using milk as a fertilizer, an empty milk carton should be filled with water and swished around, which will transfer the dregs of the milk to the water. The milky water can then be used to water the orchids.
Molasses
A teaspoon of molasses can be mixed with one to two cups of water, and then the mixture can be used to water the plant. Molasses happens to be rich in potassium.
Nitrogen
When making a natural orchid fertilizer, the key is to make sure the fertilizer provides the orchids with plenty of nitrogen since they are not potted in soil. Usually, tree bark is included in an orchid’s potting medium and most of the nitrogen in standard fertilizers is consumed by certain bacteria in the bark, so very little is left for the orchids.
Nutrients
Orchids obtain nutrients from the air, water and other elements in their native habitats. However, when growing orchids at home, these nutrients need to be provided to the plants flower[sic] (roots and leaves) optimally and grow to be healthy. Nitrogen, phosphorus and potassium in a proper balance, along with trace elements, are required when growing orchids. Healthy foliage and stems are promoted by nitrogen, the roots are strengthened by phosphorus and health(y) flowers are promoted by potassium. Boron, copper, iron and zinc are included among trace elements.
Potatoes
Potassium and a small quantity of phosphorus are provided by potatoes, both necessary for healthy orchid flowering and growth. Unpeeled potatoes can be cut into small pieces and boiled until well done. These should be cooled down and periodically added to the bark in the pot so that the orchids get the potassium and phosphorus. Alternatively, a mixture of very small diced chunks of unpeeled potatoes and small pieces of a banana can be boiled for several minutes, and the mixture can then be used once it has reached room temperature. For improved nutrient balance, magnesium can be added to the mixture by adding one teaspoon of Epsom salt. This mixture can be used to water orchids as usual.
Rice Water
Water used to boil rice is a rich source of vitamins, such as folic acid, niacin, riboflavin and thiamin, which are essential for health(y) orchid growth. The use of brown rice instead of white rice is recommended. Making this fertilizer is quite easy. The leftover water after rice is cooked should be cooled down, and then be used to water the orchid. Epsom salt can be dissolved in the rice water to balance this natural fertilizer.
Tea
Tea bags are high in nitrogen so they can also be used as a natural alternative to fertilize orchids. Nontoxic organic matter is contained in tea bags and they do not smell bad. Tea bags can be used be[sic] (by) opening them and emptying the contents into an orchid pod. The contents of tea bags can be applied once monthly in summer and spring months.
Diluted Chemical Fertilizer
Although not exactly a natural alternative, when creating a homemade batch of natural fertilizer for newly purchased orchids, traditional store-bought fertilizer can be diluted by mixing it with water to help it along.
Orchids may not require too much fertilizer, but the fertilizer being used must be nutrient-rich and this can be accomplished by using one of the above natural orchid fertilizer options, which are free from chemicals as well as other unnatural ingredients.
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