Fertilize them when they are growing.
Orchids need fertilizer to bloom. It’s better to under-fertilize than over-fertilize. A common routine is to fertilize every 2 weeks in spring and summer, and once a month in the fall and winter. Orchid experts are constantly debating how to best fertilize. In the wild, roots and leaves absorb nutrients when rainwater washes plant and animal debris over them. Orchids in pots receive some nutrients as their potting media slowly breaks down, but this may not give them all they need.