I started writing this article in response to the questions I get from newer growers when they go to buy supplies and see fertilizers touted as great for orchids. They find bloom boosters and specialized “formulas” for each type of orchid with specific months to be fertilizing. How could you possibly grow orchids without a basket of all these products?
The answer? Quite easily and without them. When you ask other growers about how or if they fertilize, it’s almost like bringing up religion or politics at a mixed gathering of people. There are lots of opinions and stories, but not so many facts or data.
So how do you sort out what is really going on and what you need to do in terms of fertilizing?
Epiphyte Roots and Nutrients
To start, orchids evolved over millions of years for a very small niche in the ecosystem that has very little outside nutrients available. They don’t grow in nutrient-rich soils with a steady source of food. To compensate, they developed ways to recycle much of what they obtain as they grow. The leaves that fall off the plant are stripped of their nutrients as they deteriorate, keeping them with the plant. In their natural habitat, they can’t afford to throw any away.
Secondly, they can only absorb so much at a time. Contact with nutrients is brief with epiphytes that grow on other plants or rocks, which are drawn from water that flows over them and their roots exposed to the air. Some orchids do grow in the ground, but those are typically in loose leaf litter and not in dense, rich soil. Epiphytic orchids have roots that are very different from your standard house plants, and their roots are well adapted to absorbing moisture from the air. They will rot if totally surrounded by soil.
Now that we know orchids don’t require a nutrient-heavy diet, we can see that they can survive well with lighter and even infrequent feedings. One of the most experienced growers at NWOS who has a large greenhouse, an extensive collection of plants. and has won many awards with his plants, infrequently fertilizes. He fertilizes occasionally, but not on a regular schedule, and yet he has thriving plants.
So why fertilize? If you have heard commercial growers speak and give their regimen of fertilizing, you need to put their practices in the perspective of their entire orchid growing culture. Often they are growing a more limited selection of genera, and sometimes specializing in just one culture of plants. They have honed their skills using light, temperature, humidity, and water, optimizing each for their plants. To fine tune the system, they work out the right mix of nutrients for their specific growing conditions, including the type of media they prefer to grow in. Without all the underlying factors in place and in balance, fertilizers would not have a great effect.
As hobbyist growers, we aren’t concerned about getting our plants to market as soon as possible. We want to enjoy as many blooms as possible and have healthy plants. Everybody grows a little differently, thus the plethora of stories, methods, and results.
Part of the art of growing orchids is observing your results and adjusting factors like light, water, temperature, and medium. Most of us have a mix of plant genera with varied needs and different media all in one environment. If we all grew only one kind of orchid, it would be easier to say how to grow it. But that is far from what we do. With so many orchid types, we just can’t resist trying several. This means different needs for several plants.
What to do? Nutrients are important, but as I said, we must first dial in the basics of culture. No fertilizer will magically make our plants grow or bloom perfectly. Olympic athletes aren’t at the tops of their games because they all eat the same diet alone. Diet is certainly important to the health and vigor of our plants, but it isn’t the only—or even most important—factor. A sick plant will just get sicker if you only focus on fertilizer.
To evaluate what makes fertilizer a good tool for your plants requires some explanation of chemistry, and how it relates to other factors like your growing medium and how you water.
Growing in the Seattle Area
We are fortunate to have good water quality in Seattle, so I would advise staying away from fertilizer with urea. Urea is inexpensive to produce, but has some negative effects because of unpredictable amounts of acidity and nitrogen it can deliver to our plants.
There is no bloom boosting fertilizer. It sounds great, but there is an overwhelming abundance of data which shows that high phosphorous fertilizers don’t stimulate blooming in plants. If your plants aren’t blooming, it probably has more to do with the amount of light they are receiving. You only need one type of fertilizer, not three or more for different types at different times of the year.
Timing of application does matter. Some plants grow all year, and some have a period of rest during which they don’t need or use the extra nutrients. I would suggest researching your specific plant’s culture and characteristics to find out if it has particular needs like rest periods.
Applying more fertilizer than your plant needs doesn’t help, and it can actually damage the plant. Fertilizer burn can cause leaf tips to darken or turn brown, an indicator that the plant has received too much. Also, extra fertilizer will accumulate at the bottom of a pot causing a build of salt which can burn the roots. More is not better.
You have probably read that you should fertilize “weakly weekly” and use ¼ of a teaspoon as the right amount. Those are good guidelines, but they lack specific details that matter.
The three numbers on the fertilizer packaging represent the percentages of nitrogen, phosphorous, and potassium, such as 13-5-15. I would recommend not using a fertilizer with a number higher than 20 for the first number, nitrogen (and remember to avoid urea in the fertilizer). You will probably be fine using ¼ teaspoon of fertilizer in a gallon of water per week.
If you forget to fertilize or haven’t been fertilizing? Kick back and relax. Your plants will be just fine. In the big picture, it is the last thing you need to be worrying about. Master the basics—light, water, temperature, choice of medium—and then learn to fine tune nutrients you provide.
For those who don’t mind getting into the weeds or are ready to delve into the details, I will be writing about that in the next article on how to fertilize