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Slow-Release Fertilizer Use Calculator

There are a wide variety of “controlled-release” and “slow-release” fertilizers on the market, and the recommendations for their use on orchids is somewhat limited.

Using guidance from the manufacturers of Osmocote, we have put together the following calculator to help determine the amount to be used.

There are three pieces of information needed to use the calculator:

  • The nitrogen content of the formula.
  • The average diameter of a round container, or the average width of a square one – in inches.
  • The total depth of the potting medium – in inches.

I say “average” diameter or width, as most flower pots are somewhat tapered.

Measure at the top and bottom of the pot and average the two measurements.