Basic Fertilization Questions

[HiOrcDen]

I bought some Miracle Gro Orchid Food, recommended by a seller, and also something I had to pick up on short notice.
I want to be sure to follow the instructions correctly. It says 'For Orchids and other indoor acid loving plants' apply 1/4 teaspoon per gallon, and apply. While it says for outdoor plants, a 1 tablespoon over soil, on the same schedule. So would an orchid kept outside, still in a typical mix such as orchid bark, receive any more than the 1/4 teaspoon? Are there different guidelines for Orchids kept in moss, or fiber?

In the long run, am I right to think I'd be better off with a strong organic mix? And one of my sellers suggests they found a great slow release mix that's better than the Miracle Gro they had been using. Are there advantages/disadvantages to slow release?

Finally, this seems tricky, how to know you have watered enough preceding the fertilizer, and not too much so that fertilizer is not absorbed, and then how to know you have thoroughly fertilized your plant, without burning? (especially with inorganic)

[estación seca]

In agriculture people measure how much fertilizer is in a solution by the concentration of nitrogen, in parts per million (ppm.)

A lot of people think orchids do better with more frequent fertilization at a lower concentration. But not everybody has the time to mix fertilizer every time they water, so many people fertilize only once a week, or once every two weeks, or once a month. Some people like to fertilize with a low concentration at every watering (10-50 ppm N.) Others like to fertilize only once a week (50-125 ppm N), or once a month (more), with a higher concentration.

Most (not all) orchids need a lot less fertilizer than most other plants. And few orchids need much fertilizer during the cooler winter period. Some do because they grow all year.

You can learn everything you need to know on the First Rays Web site. Look at the top for Free Information, then the section on fertilizer. Ray provides a nitrogen calculator. You input the nitrogen number from your fertilizer and the desired PPM of N. The calculator tells you how much to add to water to get that number. I don't know off the top of my head what the nitrogen number is in your fertilizer.

Orchids are orchids. Inside or out doesn't matter. I use the same concentration in or out.

Bark, moss, LECA doesn't really make much difference.

So long as the fertilizer provides all the minerals and nutrients, the difference between fertilizers in how your orchids grow is minuscule compared to whether you provide the proper growing conditions. The fertilizer you bought is fine. Pay attention to learning how to provide proper temperatures, light, watering and humidity before worrying about which fertilizer to use. Note many fertilizers don't have any calcium nor magnesium. If the fertilizer lacks calcium or magnesium and the water lacks these you need to use a calcium/magnesium supplement.

Don't water with plain water first. That idea was debunked in commercial agriculture over 75 years ago. You want your plants to take up as much fertilizer as possible. Water dry orchids with your dilute liquid fertilizer. If you water with plain water the roots will soak up plain water and have little capacity for absorbing the fertilizer solution. Your fertilizer solution should be dilute enough not to harm roots, and you shouldn't rely on tricks so you can use a solution that is too concentrated. This is the big reason why people like to use a lower fertilizer concentration but more often.

Most of the larger epiphytes don't have any trouble with fertilizer concentrations of nitrogen around 150ppm. Cloud forest orchids and slipper orchids prefer much less than this. If you go to the Sunset Valley Orchids cultural information page, Fred Clarke tells you how he applies MSU fertilizer to his plants. If your Miracle Gro has a different nitrogen number, you can use Ray's calculator to determine how to mix your fertilizer to get numbers similar to what Fred uses.

[RoseSD]

Could you clarify where Ray's calculator is?

[Dusty Ol' Man]

Originally Posted by RoseSD

Could you clarify where Ray's calculator is?

First Rays LLC › Using Science & Logic to Advance Orchid Growing

[Ray]

Fertilizer PPM Calculator

Or, if you just want to be in the ballpark, use the flowing estimates:

For 25 ppm N, 2/%N = teaspoons/gal, or 2.3/%N = ml/L

So if I want a 100 ppm N solution of MSU RO @ 13.2% N, that would be 2/13.2=0.1515. Multiplied by 4 = 0.6 teaspoon (I’d just round down to 1/2), or if you want metric measures, 2.3/13.2=0.1742 x 4 = 0.7 ml/L

[RoseSD]

Originally Posted by Ray

Fertilizer PPM Calculator

Or, if you just want to be in the ballpark, use the flowing estimates:

For 25 ppm N, 2/%N = teaspoons/gal, or 2.3/%N = ml/L

So if I want a 100 ppm N solution of MSU RO @ 13.2% N, that would be 2/13.2=0.1515. Multiplied by 4 = 0.6 teaspoon (I’d just round down to 1/2), or if you want metric measures, 2.3/13.2=0.1742 x 4 = 0.7 ml/L

What about the amount of application? Using the solution instead of water in that watering including soaking method, or just add enough by spraying to wet the top of the soil?

[Ray]

Originally Posted by RoseSD

What about the amount of application? Using the solution instead of water in that watering including soaking method, or just add enough by spraying to wet the top of the soil?

I am a proponent of flooding the potting medium at each watering, as it flushes, saturates, and aerates all in one step. Over winter, when the plants are indoors, I mostly use a heavy spray on the media surface until drainage starts, which is admittedly less thorough.

We really don't know how much of what we apply is actually absorbed, because we don't know the retention of all potting media, we don't know how well solutions are spread around the pot as the water evaporates, and we don't know the contact area of the root system in relation to those. My recommendations are just the culmination of years of growing and observation, using the techniques I employ.

I did a calculation (AKA - "sheer folly") based upon the chemical reactions that fix carbon and the resulting nitrogen and water requirements, based upon an assumption that a plant gains one pound of mass in four years (Phals, maybe?), and if it was 100% absorbed, we could water 1 pint (16 fluid ounces, or about 570 ml) a week using a 55 ppm solution (assuming about 50 of that was N).

[HiOrcDen]

Originally Posted by Ray

I am a proponent of flooding the potting medium at each watering, as it flushes, saturates, and aerates all in one step. Over winter, when the plants are indoors, I mostly use a heavy spray on the media surface until drainage starts, which is admittedly less thorough.

We really don't know how much of what we apply is actually absorbed, because we don't know the retention of all potting media, we don't know how well solutions are spread around the pot as the water evaporates, and we don't know the contact area of the root system in relation to those. My recommendations are just the culmination of years of growing and observation, using the techniques I employ.

I did a calculation (AKA - "sheer folly") based upon the chemical reactions that fix carbon and the resulting nitrogen and water requirements, based upon an assumption that a plant gains one pound of mass in four years (Phals, maybe?), and if it was 100% absorbed, we could water 1 pint (16 fluid ounces, or about 570 ml) a week using a 55 ppm solution (assuming about 50 of that was N).

Thanks to all for your advice! So in this case, how do you flood the medium? Do you soak the whole pot in a plastic tub, or something along those lines, with the less concentrated solution for fertilizing with every watering? If not, what constitutes flooding?

I would think that at a certain point wood chips, for example, would be totally saturated with the fertilizer solution, which I would think wouldn't harm the plant. I would also imagine, when flooding, then the roots can also become saturated, which would be safer at lower concentration. If I am correct, then would this not make a very thorough flooding with lower strength fertilizer with each watering, more efficient for growth as well as safer for the plant? Just speculating!

[Ray]

Originally Posted by HiOrcDen

Thanks to all for your advice! So in this case, how do you flood the medium? Do you soak the whole pot in a plastic tub, or something along those lines, with the less concentrated solution for fertilizing with every watering? If not, what constitutes flooding?

I would think that at a certain point wood chips, for example, would be totally saturated with the fertilizer solution, which I would think wouldn't harm the plant. I would also imagine, when flooding, then the roots can also become saturated, which would be safer at lower concentration. If I am correct, then would this not make a very thorough flooding with lower strength fertilizer with each watering, more efficient for growth as well as safer for the plant? Just speculating!

I don’t “soak” my plants by submerging the pots, I use a hose with a “water breaker” or “rain head” on the end, so the flow resembles heavy, air-entraining rainfall, and let it get fully flowing through the medium. I think that is probably the best way to do so.

Water is, by far, the most important factor to growth, so I think you are correct that the best thing you can do is find a way, through selection of potting medium and container, to be able to water heavily and often, and yes, with a tiny bit of fertilizer.

Adequate water at the root system is a trigger for the plant to open its stomata for gas exchange, allowing more carbon dioxide intake, which leads to faster carbon fixation - growth. If you grow in a medium that must dry out to avoid suffocating the roots, you are forcing the cycling of that process on and off, which must slow things down.

Granted, this is a very generalized and simplistic description of the “base process”, as plants handle such activity differently, but the concepts are still applicable.

[HiOrcDen]

Apologies, I mistakenly added an unnecessary post, and not sure how to delete it!

---------- Post added at 01:24 AM ---------- Previous post was at 01:00 AM ----------

Originally Posted by Ray

I don’t “soak” my plants by submerging the pots, I use a hose with a “water breaker” or “rain head” on the end, so the flow resembles heavy, air-entraining rainfall, and let it get fully flowing through the medium. I think that is probably the best way to do so.

Water is, by far, the most important factor to growth, so I think you are correct that the best thing you can do is find a way, through selection of potting medium and container, to be able to water heavily and often, and yes, with a tiny bit of fertilizer.

Adequate water at the root system is a trigger for the plant to open its stomata for gas exchange, allowing more carbon dioxide intake, which leads to faster carbon fixation - growth. If you grow in a medium that must dry out to avoid suffocating the roots, you are forcing the cycling of that process on and off, which must slow things down.

Granted, this is a very generalized and simplistic description of the “base process”, as plants handle such activity differently, but the concepts are still applicable.

Thank you for the enlightenment! How do you apply fertilizer when watering with a hose? Do you use the hose attachment that holds and dispenses fertilizer automatically as you water, along with the rain head you mentioned? (maybe both features in one attachment?) and if so what concentration do you place in the attachment? (If it's not too much trouble could you tell me the name of the attachment you use?)

How do you water very small plants, like in 2-3" pots, just shower over them? Also, when you say tiny amounts of fertilizer, is that the 25-50ppm that Estación Seca described?

Again, I truly appreciate all the tips. And sorry for the barrage of questions, I really want to get the right practices down! And you seem to have the right answers lol

btw will check your website for answers too!