using a proportioner to fertilize an orchid collection

Asked June 23, 2015, 6:34 PM EDT

I am purchasing a Dosatron fertilizer proportioner to feed my greenhouse orchid collection. Can you tell me how much soluble orchid fertilizer to mix in a 5 gal. bucket so that at a 1:100 setting, my orchids will be getting the equivalent of 1/2 tsp. of diluted fertilizer per gallon of water

Curry County Oregon

1 Response

There are 768 teaspoons in a gallon and multiply that times 2 per teaspoon times 5 gallons and you would get 7680 1/2 teaspoons in 5 gallons of liquid fertilizer solution. I take it that you figured out the part about diluting the amount that you bought to 1:100, because that's what you really need to know, and as I don't have those numbers, I don't know how many gallons it would make(?) Does it tell you on the fertilizer bottle how much solution that it will make?

There appear to be several factors to consider in calculating fertilizer for orchids. we would need to ask you more questions to be definitive. I think, however, this information will point the client in the right direction.

Hopefully the Dosatron manufacturer will include detailed instructions. Their website is

The factors for consideration are:

1. Which Dosatron unit did you purchase? (D25F1-11GPM, D14MZ2-14GPM, etc.) There are dozens.

2. The alkalinity of your water source. See

3. What kind of nitrogen PPM you hopes to achieve. See

4. The manufacturer’s suggestion instructions. See

This information may be helpful in your calculations:

1 gallon = 768 teaspoons

5 gallons = 3840 teaspoons

1 gallon = 128 ounces

5 gallons = 640 ounces

I am going to forward this information to a Master Gardener who has done a lot of work raising orchids to confirm. Please feel free to contact me, Scott Thiemann, at OSU Extension in Curry County at 541-247-6672 if you have more questions or are curious to see if we got any further feedback.


Just wanted to be sure that you saw the additional info included: One of our orchid growers suggested that you add your fertilizer (of what they tell you on the bottle) at half strength each time you water, usually once a week, more in hot weather. Of course, this may not be necessary if your climate is much cooler than Brookings. She also suggested getting in touch with Mike Oliver (American Orchid Society) at: . Hope that helps you