Fertilizing Orchids 

Fertilizing orchids is a relatively simple procedure, but different species may have different requirements. In nature orchids absorb most of their nutrients from animal droppings, leached minerals, and decaying leaves or other organic matter in their environment. Because most orchids are epiphytes and get their nutrients this way, we mimic this by giving our orchids low doses of fertilizer on a semi regular basis. We can stop fertilizing during the bloom period even though there are fertilizers on the market that promote fertilizer for the bloom stage, however it is not necessary, especially if we feed our orchids with a high nitrogen, low phosphorous, high potassium fertilizer especially made for orchids. Just as it is with watering, it is best to err on the side of slightly under fertilizing than overfertilizing. 

Types of fertilizer

When it comes to fertilizing orchids, we have two choices, chemical fertilizer or organic fertilizer. Which one is best for our orchids? Well both actually, and there is no harm in combining the two methods by altering every other month, or even every other feeding. This way our orchids can benefit from a wider variety of nutrients. And although organic fertilizer companies sometimes claim in their marketing materials that organic fertilizers are more natural than  chemical fertilizers, at the end of the day, all fertilizers are salts that are absorbed by plants to aid and promote growth. An extremely beneficial organic treatment is the application of compost tea to the roots and leaves twice per year. You can read more about how to make a compost tea here. 

Chemical Fertilizer

Chemical fertilizers come in crystal salt formation and in liquid applications. Most chemical fertilizers will have three numbers on them such as 20-20-20, denoting the amount of nitrogen, phosphorous, and potassium (NPK) as a percentage of the weight of the container it is in. For example if a bag of fertilizer weighs 10 lbs and the ratio of NPK is 20-20-20, that means that the bag contains 20% Nitrogen or 2 lbs (10lb x .20 = 2lbs), 20% Phosphorous (2lbs), and 20% Potassium (2lbs). The remainder of the fertilizer would contain macro nutrients such as Calcium, Magnesium and Sulphur as well as micronutrient trace minerals of Boron, Copper, Iron, Manganese, Molybdenum, and Zinc. 

Organic Fertilizer

Organic fertilizer is fertilizer than comes from living or biological sources (kelp, compost, worm castings, bat guano, animal manure) and including animal waste sources such as bloodmeal or bone meal. Some growers prefer to use only organic methods and organic fertilizers. Organic fertilizers are generally a little gentler and lower in NPK fertilizer content. Additionally, they are not as reliably balanced in NPK formulas and often using an organic method involves the use of different organic material sources to achieve good nutrient quotients. For this reason, fertilizing orchids with organic fertilizer in addition to chemical fertilizer is a great way to provide a wide variety of nutrients. My personal method is to alternate from chemical to organic fertilizer on a monthly basis, as well as providing a compost tea foliar and root application twice per year including Azomite A-Z minerals in the tea. 

Methods of fertilizing orchids

How you choose to fertilize your orchids is a matter of choice. You can choose to use a chemical only method, an organic only method, or a combination of the two methods, alternating on a weekly or a monthly basis. When choosing a chemical based formula, choose a brand that is made specifically for orchids. Orchid based formulas generally do not use Urea based fertilizer and a balanced 20-20-20 NPK formula works well for most orchid species. Most formulas will recommend fertilizing your orchids on at least a monthly basis, many orchid growers like to fertilize weekly. There is an adage in the world of orchid growing to water weakly weekly. Instead of using the normal recommended dosage on the instruction label of your fertilizer, use 1/4 of the amount on a weekly basis. Follow the same guidelines with organic fertilizers. If you choose to fertilize on a weekly basis make sure that you use 1/4 of the recommended monthly dosage. It is better to err on the side of slightly less than more. Personally, I like to alter between chemical fertilizer and organic fertilizer on a weekly basis using a quarter of the dosage that is recommended whether it be chemical or organic fertilizer. 

Application

If you have a relatively small amount of orchids, application can be as simple as mixing your fertilizer with water in a watering can. Follow the dosage recommendations mentioned above. If you have many orchids to fertilize and water, then a 5 gallon pressure sprayer works well. Again follow the dosage per gallon recommended on the instruction label of your fertilizer and use one quarter of that amount if fertilizing on a weekly basis.