Super-Simple Orchid Feeding

[raybark]

On Facebook and in orchid forums like this, one of the most common questions is "What's the best fertilizer?".

While there are as many opinions on that as there are growers, and the subject area is certainly ripe for speculation and experimentation, what if you don't want to go into such detail, and just want to do what you can to grow them? This list of bullet-points will show a simple yet adequate approach.

►Fertilizer formula, in general, is not critical.

►If you use a pure water source - rain, RO, distilled, etc. - you must supplement Mg and Ca. You can use an ordinary fertilizer and use supplement additives, but I find it easier to use a formula already containing them. In order of amount contained, K-Lite has the most, followed by MSU RO and Jack's Cal-Mag.

►There is no need to switch formulas if the one you're using is nutritionally complete.
Nitrogen is, by far, the most important nutrient. I strongly urge growers to use nitrogen content as the feeding control factor - analogous to calorie counting for people.

►Since we have no idea of the mass uptake by the plant, we can use fertilizer concentration and frequency of application as a control mechanism.

►A good, general feeding regimen should supply between 75 and 125 ppm N per week. Don't let that scare you - it's easy to translate that to easy to use measurements:

◙Divide 8 by the %N in the formula. The result is teaspoons/gallon to mix for the middle of that range, giving you room to round up or down for measuring convenience. Here are a few examples:

•K-Lite Orchid/Epiphyte Fertilizer contains 12.9% nitrogen. 8/12.9=0.62. Anywhere between 1/2- and 3/4 teaspoons per gallon keeps you in the recommended range.

•MSU Fertilizer for Well Water contains 19% nitrogen. 8/19=0.42, so use 1/3 to 1/2 teaspoon per gallon.

•Miracle-Gro Orchid Food is a 30% N formula. 8/30=0.267, so 1/4 teaspoon/gallon is appropriate.

◙If you work with metric measures, dividing 9.2 by the %N gives the result in ml/L.

◙If you feed every two weeks (that's the longest interval I recommend), double the numerator in that simple math.

►If you decide to change fertilizer formula, use the same nitrogen concentration, but do not expect to see a change in your plants' growth and flowering. If that's your goal, maintain a steady course with your feeding and look instead at other aspects of your overall culture.

[Arne]

Great information Ray.

I weigh everything simply because I'm used to that and have some good balances. So my only question is, what is the conversion weight to volume? One teaspoon is 5 mL if I'm not mistaken.

[raybark]

Thanks, Arne.

Yeah, that's a reasonable mass-to-volume ratio, but I still think it's easier to control by ppm N.

[Brutal_Dreamer]

Thank you, Ray!

Cheers,
BD

[Sheryl]

Thanks Ray!!