How do bromeliads grow on trees or rocks without being parasites?

Bromeliads that grow on trees or rocks are classified as epiphytes, not parasites. They use these surfaces solely for physical support to reach better light in dense environments, rather than drawing water or nutrients from the host plant.1234

Unlike parasitic plants, which utilize a specialized organ called a haustorium to penetrate a host and extract resources, bromeliads remain independent. They obtain their necessary moisture and nutrients through other means:3

• Water Absorption: Many bromeliads absorb water directly from rain and atmospheric humidity using specialized hairs on their leaves.15
• Nutrient Collection: Tank bromeliads feature a rosette of leaves that forms a hollow reservoir, collecting water, windblown dust, and organic debris. The decomposition of this material provides the plant with essential nutrients.261

Because they do not harm the plants they grow upon, they are considered non-parasitic, using the host merely as a structural platform.34