One of the things most of us know about plants is that they are green-- they photosynthesize using chlorophyll, sunlight, water, and nutrients they extract from the soil or air to produce their own food. However, some plants aren't green and thus can't produce their own food. How do they survive? They use two different strategies-- some are saprophytes and some are parasites.
Saprophytes are organisms that obtain nourishment from dead or decaying organic matter. Coral roots (Corallorhiza sp.) are ground-dwelling saprophytic members of the orchid family that grow in they park. They form a partnership with soil fungi (mycorrhizae) to obtain nutrients from the decaying matter in their environment. Their tiny, dust-like seeds contain almost no food for the embryo they encase, and they must come into contact with soil mycorrhizae almost immediately upon being shed from the parent plant to have any chance of survival. It is thought that coral roots form partnerships with a limited number of types of fungi, and thus their distribution may be determined by the presence of those specific fungi.
Parasitic plants tap into other living plants to obtain their nourishment. Some rely on underground fungal threads (hyphae) to tap into the roots of their host plants. Examples of these ground-dwelling parasitic plants found in Rocky Mountain National Park include pinesaps (Hypopitys monotropa), pinedrops (Pterospora andromedea), and broomrape (Aphyllon sp.).
Other parasitic plants, such as mistletoes, grow directly on their host plants. Mistletoes (Arceuthobium sp.) grow on the branches of their host trees, and can most easily be located by scanning the branches for irregular looking "wads" of growth. The "wads" can be the mistletoe plants themselves, or the mistletoe may also cause their hosts to grow into a misshapen mass called a "witches broom." (Witches brooms may also be caused by rusts or viruses.) Once located, mistletoes clearly are different from their plant hosts. This is especially true in the park, where their hosts are conifers, while mistletoes clearly do not have needles. They do, however, have explosive sticky seeds to aid in their spread, so be careful if you touch them!