Big red sage occurs in the Edwards Plateau, a geographic region with hot, dry summers and mild winters, significant annual variation in rainfall, and frequent, prolonged droughts. The amount and frequency of rainfall are greatest in May, September and October. Wide extremes in rainfall, from torrents to extended droughts, create harsh conditions that restrict plant growth over much of the Edwards Plateau. 

The plant grows on shallow, rocky soils found on vertical bluffs, ledges, and steep slopes along streams and ravines. These narrow canyons create shaded, moderately moist habitats, particularly along north-facing slopes. Most big red sage plants are found in light to heavily shaded areas, but some grow in full sunlight on north-facing slopes of narrow canyons. Because of where it grows, streamside populations of big red sage are particularly vulnerable to flash floods. 

Populations of big red sage are sustained where rainwater infiltrates through porous limestone strata of the vadose hydrological zone (the portion that is above the water table) and seeps to the surface. Although small portions of some populations may also be sustained by seepage from the Edwards-Trinity or Trinity aquifers, most populations are not dependent on aquifer levels.

When flowering, the aptly named big red sage has impressive 5-foot-tall (1.5 meters) stalks covered with reddish-purple flowers.

Big red sage's stalks emerge from a basal rosette of smooth, thick, dark green leaves, which can grow up to 5 inches (12 centimeters) long. Individual rootstocks produce one to several four-sided flower stalks, which can reach a height of 5 feet (1.5 meters). The flower stalks may be simple or have one to several primary branches. The overall tubular flowers are about 1.5 inches (4 centimeters) long. 

Big red sage’s crimson flowers are tubular with a three-lobed upper lip and a 2-lobed lower lip. The base of the flower (calyx) is green and becomes purple with age. 

Big red sage is a perennial species that reaches maturity, from seed germination to the development of mature seeds, in as little as 16 months. The plant remains in a vegetative state as its root systems develop, and it is likely that carbohydrates are stored in the roots. Its leaves die back during drought or cold weather, and new leaves emerge when moisture and warmth return. 

Big red sage flowers opportunistically from May through November in response to rainfall and the persistence of soil moisture. Hummingbirds pollinate the species, acting as important vectors for the plant’s gene flow because individuals of big red sage may be separated by over half a mile (0.5 to 1.0 km). 

Individual plants of big red sage have been documented to live at least 10 years. Like many perennial plant species, this species has an indeterminate lifespan with no upper limit. New rosettes often branch from established rootstocks and may outlive the original plant (and others in succession), so it is possible that individuals present today may have originated from a seed that germinated many decades ago. 

Known causes of mortality of big red sage include herbivory from white-tailed deer and introduced ungulates, flooding, and collection from the wild. Additionally, severe or extended drought is also assumed to cause mortality.

The perennial big red sage can reproduce both vegetatively and sexually. Big red sage’s flower shape facilitates pollination by hummingbirds. Black-chinned hummingbirds (Archilochus alexandri) are the most abundant species throughout the plant’s range and flowering period and are known pollinators of big red sage. However, other hummingbird species may also pollinate big red sage. A unique structure structure
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In addition to sexual reproduction, big red sage reproduces vegetatively, although to a limited extent, by means of multiple rosettes (ramets) arising from a single rootstock. The underground connections between rosettes may not be evident without disturbing the soil, and it is possible that multiple rosettes that originated from a single individual could develop independent root systems and eventually become separated from each other.

Big red sage might be mistaken for other red-flowered Salvia species of the Edwards Plateau, such as cedar sage and tropical sage (S. roemeriana and coccinea, respectively), as well as cardinal flower (Lobelia cardinalis) and red-flowered penstemons.