Epidendrum radicans is a terrestrial orchid species, popularly called the "Rainbow Orchid" or "Fire Star Orchid." A special characteristic of this genus is the tendency to extend its roots along the entire length of the stem. It is found in Puerto Rico, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, Panama, Venezuela, and Colombia.
Like other members of the subgenus Amphioglottium, Epidendrum radicans is a sympodial species that has stems which do not develop thickened pseudobulbs, but are covered by overlapping sheaths extending to the basal area of the apically inserted inflorescence. A particular feature of the subgenus is the presence of a labellum adnate (fused) to the column—towards its apex—being trilobed, as in other members of the Schistochila section (with the typical lacerated lobes of the Carinata and Tuberculata subsections).
The chromosome number of an individual collected in Ecuador was determined to be 2n = 60. However, other data indicate values such as 2n = 40, 2n = 57, 2n = 62, and 2n = 64 for this species.
A common ruderal species in its native regions, Epidendrum radicans is frequently found as a weed along roads and railway embankments in Central America, where it forms, along with many other members of the Schistochila section, species complexes often confused with each other, including Epidendrum calanthe, Epidendrum cinnabarinum, Epidendrum denticulatum, Epidendrum erectum, Epidendrum fulgens, Epidendrum ibaguense, Epidendrum imatophyllum, Epidendrum incisum, Epidendrum schomburgkii, Epidendrum secundum, and Epidendrum xanthinum.
Another species, outside the genus, with which it is sometimes confused due to the flowers, is Prosthechea vitelina, but careful observation of the pseudobulbs of the aforementioned taxon is relevant for correct diagnosis. The diagnostic criterion for Epidendrum radicans is the tendency of the species' specimens to develop roots along the entire length of the stem—other members of the group it can be confused with develop roots only in the basal area. As an additional factor, radicans flowers are always resupinate (upside down), compared to members of the Epidendrum secundum complex, or Epidendrum fulgens and other species, where this aspect is not present. Also, Epidendrum radicans flowers do not contain nectar.
The resemblance to other species is not accidental, as radicans belongs to a complex of ruderal weeds that includes a number of taxonomically distinct species, both segetal and ruderal, unrelated but ecologically similar; they are also pollinated by the same insect species, live in the same habitat, and are easily confused—representing a good example of convergent evolution, where several different species, through environmental adaptations, come to exhibit the same physical characteristics under adaptive pressure.
Epidendrum radicans blooms most frequently between spring and autumn, producing terminal inflorescences ranging from 25 to 100 cm in length. The seeds of this plant are quite small, about 320 seeds per milligram. It is a native plant from the cooler regions of Central America, growing at altitudes between 500 - 2500 m, in pine and beech forests.
Unlike many other orchids, it needs direct sunlight if possible. Ideal are temperatures between 15 and 32 °C during the day, and 10 - 21 °C at night. If the plant is kept outside, it will need to be moved indoors when the freezing period comes.
It tolerates various soil types and can be grown in plastic or clay pots, in a mix of moss, perlite, sand, or gravel. The pot must have drainage holes, and the soil mix must also ensure good water drainage. If kept in a clay pot, it will need more frequent watering. Generally, it does not require repotting, but soil should be added at the base as it decomposes or washes away during watering.
Humidity is very important; it should be watered abundantly but never allowed to pool.
It produces denser flower spikes and greener leaves if regularly fertilized with a balanced fertilizer containing nitrogen, phosphorus, and potassium. Indoor-grown plants become very bushy if fertilized with too much nitrogen.
Epidendrum radicans orchid is amphitolerant (able to withstand wide pH variations without affecting its growth, development, and reproduction) in terms of temperature, and can be successfully grown across a wide range of temperatures, almost down to the freezing point. It requires abundant light, frequent fertilization with a balanced fertilizer, ample watering without allowing water to stagnate, making it an easy species to grow for beginner enthusiasts who lack experience or the ability to provide special conditions.
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