Fertilizer is not "food" as we think of it because the plant's energy and its structure (cellulose, lignin) comes from atmospheric CO2. Fertilizer salts are needed mostly for physiological functions/chemical reactions associated with new leaves and root tips. Flowers and capsule growth are mostly structural additions (atmospheric CO2) so relatively low levels of nutrients are needed. These can be supplied, for the most part, by stored nutrients in the plant and left over nutrients in the medium. By fertilizing heavily (especially with high nitrogen) during the flowering season, the orchid may be convinced to reduce flowering and resume vegetative growth.

Plants with a high ratio of seed/fruit/flower to plant weight, like tomatoes, corn etc have a greater need for nutrients than orchids.

Young orchids tend to have a higher flower structure to plant structure ratio so can use more nutrition, but a big ol' orchid can usually flower its head off even if you stop fertilizing it.

To answer your question more simply. When you fertilize normally during flowering and low growth periods most of the fertilizer is wasted or builds up in the medium. And, if you are using a traditional orchid fertilizer high in nitrogen 30:10:10 the number of flowers may even be reduced. Bloom booster fertilizers are simply low nitrogen formulas.

Many of us with mixed collections and don't want to fool with any of this theory and just treat all of the plants the same all year round, but use a balanced fertilizer with moderate nitrogen levels.

I am also in the general fertilizing camp. As was mentioned, it is mostly because my collection is highly varied, but also because since orchids are slow growing, they need very little. Most of us give our orchids too much and the throw away what the can't use.

Fertilizer is more like vitamins than food.

LOL richardol - I like your description of fertilizer being a vitamin.

Brooke