Pachystachys coccinea aka Cardinal's Guard

Pachystachys coccinea, known as cardinal's guard, belongs to the Acanthaceae family. It is an upright evergreen shrub or sub-shrub from tropical America. Kew gives its native range as Trinidad to Peru. Missouri Botanical Garden describes the West Indies and tropical South America. It grows in a wet tropical climate. The RHS lists Jacobinia coccinea as a synonym.

In its native habitat, this shrub reaches 2–6 feet [0.61–1.83 metres] tall. Container plants stay much shorter in the St. Louis area. The garden listing gives a height of 2 feet [0.61 metres]. It gives a spread of about 3 feet [0.91 metres]. Dark green leaves have an oval to elliptic shape. Each leaf can reach 0.5 feet [0.15 metres] long. The plant keeps its leaves through the year.

Bright scarlet flowers form spikes at the ends of stems. Each narrow, tube-shaped flower has two lips. Green bracts surround the flowers along each spike. The red blooms provide the plant's main garden display. In its native climate, flowering can continue through the year. In St. Louis, most blooms appear during summer. Its flowering season therefore depends on where it grows.

Grow it in full sun for the stated preferred conditions. It also accepts a site with some shade. Give it rich soil that holds moisture but drains well. Keep soil evenly moist, and do not let it dry out. Warm, humid summers suit its growth. Missouri Botanical Garden rates its water needs as medium. Reduce watering during winter rather than following the summer routine. Its listed winter hardiness covers USDA zones 10–11.

Outside those zones, gardeners can use it as a summer annual. It also suits containers, greenhouses, and year-round indoor growing. Pots allow gardeners to move plants indoors for winter. Indoors, give it a warm, humid spot with plenty of sun. For winter care, place it near a sunny window. Keep the temperature at or above 65°F [18°C]. Its evergreen leaves and scarlet flowers offer interest in these settings. Watch for aphids, whiteflies, and spider mites. Indoor plants need close checks for these pests.