Generally orchids require less fertilizer than most other plants. It is far more harmful to give an orchid too much orchid fertilizer than too little. In fact, orchids can go on living happily without any added nutrients. But feeding them the right amount of orchid fertilizer at the right time can lead to more brilliant flowers and stronger growth.
Personally, I don’t like to lose sleep over fertilizing my orchids, so I follow the simple “weakly weekly” routine, which means I supply half or even a quarter of the amount prescribed on the label on a weekly basis. And at least once a month, I water without any fertilizer to flush out any mineral build-ups in the pots. In the winter, or when the plants are not actively growing, don’t fertilize the orchids at all. Your plants have no need for extra nutrients during that period.
Most orchids are epiphytes. That means they live on trees with their roots clinging on branches and hanging in the air. They only receive nutrients from rotten leaves, bird droppings and dust that are washed down by rain. As you can imagine, the minerals pass by very quickly and in small quantity. To be the super survivors orchids are, they learn to live and flower with very little feeding. Lithophyte orchids (live on rocks) also live under similar environment and are equally efficient in their nutrient use.
Terrestrial orchids, on the other hand, have roots that live in the more mineral-rich ground. As a result, they are used to absorbing more nutrients. Therefore, you should apply little more fertilizer than their epiphyte counterparts.
In serious cases, overfeeding your orchids can lead to their tragic deaths. But even short of dying, overfeeding negatively impacts your plants. Your orchids may not flower, produce fragile growths and generate many leads without any maturing normally. The roots of the orchids can also be burned and die. Orchids with no viable roots cannot absorb water, so they become dehydrated. Thin-leaf orchids such as Cymbidium and Miltonia will have leaves with burned tips. To remedy this situation, flush the pots with plain water to get the fertilizer out. In serious cases, you should re-pot your plants. If the orchid is in very sorry condition, you are better off chucking it in the dumpster and getting a new one (and not over fertilize anymore)!
Orchids need 16 nutrients—nine macronutrients and seven micronutrients. Macronutrients are so called because they are needed in larger quantity. On the other hand, micronutrients, though equally critical to the health of orchid, are need in very small amount. These nutrients are:
- Hydrogen (H) – food production
- Carbon (C) – food production
- Oxygen (O) – food production
- Nitrogen (N) – leave and stem growth
- Phosphorus (P) – flower production
- Potassium (K) – general good health and orchid issue building
- Calcium (Ca) – cell wall formation and cell activity regulation
- Sulfur (S) – combined with nitrogen and phosphorus to produce proteins
- Magnesium (Mg) – part of chlorophyll molecule and thus for producing food
Micronutrients – catalysts in vital chemical reactions
- Iron (Fe)
- Manganese (Mn)
- Zinc (Zn)
- Copper (Cu)
- Boron (B)
- Molybdenum (Mo)
- Chlorine (Cl)
Hydrogen, carbon and oxygen are available from air and water, so you don’t need a fertilizer that includes these elements. Most fertilizers also do not include any of the micronutrients because the trace amount can be found in the tap water and potting material. So that means most plant food only includes nitrogen, phosphorus, potassium, calcium, sulfur and magnesium.
If you are using rain or reverse osmosis water, you need to find a fertilizer that contains all of the macronutrients and micronutrients, since rain and reverse osmosis water don’t come with them. But the “complete fertilizer” in the market only means that it contains nitrogen, phosphorus and potassium. It’s really not that complete, so read the fine print on the label.
All fertilizers have 3 numbers printed on their labels. For example, you might see 20-10-10 or 20-20-20. The numbers represent the percentages of nitrogen, phosphorus and potassium respectively. These three nutrients are the most prominent on the label because they are needed in larger quantity by your plants.
Different growers have their own preference of fertilizer with different ratios of these nutrients. One consensus is that if your potting material has bark or tree fern, you should use a fertilizer with slightly higher nitrogen content, such as 20-10-10, because the break-down process of bark requires nitrogen, and hence you need to supply more of it. However, fertilizer with too much nitrogen could promote growth at the expense of flowers, so don’t go overboard with your nitrogen. For other growing media, use a balanced formula, such as 20-20-20.
Orchid Fertilizer vs. Other Plant Fertilizer
What is the different between orchid fertilizer and regular plant fertilizer? The simple answer is nothing. Regular plant fertilizers also have different nutrient contents just like orchid fertilizers. What you need to look at is the actual nutrient contents and percentages. However, the instructions on the regular fertilizer label tell you to use a higher concentration; therefore, when feeding orchids with these fertilizers, you should only use half or a quarter of the amount prescribed on the label.
It’s common for orchid growers to periodically add some supplements to their fertilizing routine. One of the most highly recommended supplements is Superthrive. Many hobbyists swear by the success it brings. The “secret sauce” ingredient is not revealed, but it is reported to be vitamins and hormones. Many orchidists also use it to ease the “traumatic” experience of repotting. They just dissolve a couple of drops of Superthrive in a gallon (3.78 liter) of water. However, some people did report that too much Superthrive can potentially lead to deformed plants and flowers.
Another additive is epsom salt, which provides magnesium to your orchids. Magnesium has a reputation as a “bloom booster.” Some people believe their ever-so-reluctant-to-bloom orchids give them flowers after applying epsom salt. Magnesium is supposed to already exist in your municipal water, but perhaps the concentration is lower in some locales than others. If you water once a week, just add one tablespoon of epson salt to one gallon (3.78 liter) of water.
Inorganic vs. Organic
Inorganic fertilizer has minerals that are highly soluble and are readily available for absorption. Usually the fertilizer can be detected in the plants’ system one hour after feeding. On the other hand, organic fertilizer requires a break-down process to release the nutrients to the plants. Because of this process, the nutrients provide slower releases and the potting material breaks down quickly, which requires repotting more frequently. Organic fertilizers are also more expensive and get washed away because orchid potting material is quite open. But the health benefits of organic fertilizer trumps the disadvantages. Plants are usually more vigorous and can withstand trauma more gracefully.
Fish emulsion, bone meal, blood meal, cottonseed meal, cow manure and chicken manure are organic fertilizers. But you need to use larger quantities compared to inorganic fertilizer to compensate for the lower concentration. Put the organic fertilizers in water and shake it vigorously. Let it sit for a day and use the liquid to fertilize. But please promise me that you will only use cow and chicken manure on orchids that grown outside of your house as I imagine they would not provide the freshest fragrance.
Time-released fertilizers are usually to be avoided on epiphyte orchids because of their high concentrations. But I’ve seen people use them on Cymbidium and Miltonia with excellent results. Just to be safe, apply sparingly in the spring only, when the plants are starting to grow. You can always increase the amount in the following year if your plants seem to like it. A popular brand of time-release fertilizer is Dynamite (red label).