The name scarlet sage could actually refer to either Salvia splendens or Salvia coccinea, two different but equally impressive plants when the gardener knows how to grow them. Both plants are widely known as scarlet sage and both plants are named after their lovely red blooms. Neither plant, unlike the sage in your kitchen, is edible unfortunately. Either can make a bright addition to your backyard garden, though.
Salvia splendens is a tender perennial that grows in United States zones 8, 9 and 10. This type of scarlet sage can grow to one and a half feet tall with a one foot spread. The 'Red Blazer' variety has long spikes of tubular deep scarlet flowers above toothed lance-shaped leaves that come in pale to dark green. This plant kind of looks like the herb sage, only dark red instead of green. It's an ornamental that performs well in the summer. Salvia splendens likes to be planted in full sun. It will bloom in late summer and early autumn. You should plant your Salvia splendens in spring in a sunny, well-drained spot that you amend with compost or well-rotted manure. You can sow the seeds directly into your garden once you are certain that the last frost of the winter has passed. Begin by soaking your seeds in tepid water for two days since Salvia spendens can be slow to germinate. Plant the seeds about one foot apart from one another and keep the soil uniformly moist. You can cover the ground with mulch to help you conserve water. Feed your scarlet sage every other week with a balanced, water soluble fertilizer according to the instructions on your fertilizer. If your scarlet sage attracts insects such as whiteflies, aphids mealybugs or spiders, apply some insecticidal soap or introduce a natural predator like ladybugs into your garden. Pinch your sage's growing tips to encourage bushy habits and don't forget to remove dead or discolored leaves.
Unlike the ground cover Salvia splendens, Salvia coccinea—a subshrub perennial in warmer climates and and annual where winter temperatures regularly dip below freezing—is quite hardy. This scarlet sage reaches two to three feet in height and has two inch triangular leaves on long stems opposing one another on a square stem. Salvia coccinea is an American mint with big, trumpet shaped, showy flowers bright red in color and about one inch long. They are arranged around the upright stem higher up than the leaves. These flowers appear continuously from early summer until the first frost of winter. Salvia coccinea likes full sun and dry soil; it even tolerates drought with no supplemental watering. It can be planted from seed directly into your garden. Once you establish your Salvia coccinea in warmer climates your plants should persist through reseeding. This scarlet sage persists in natural area gardens without becoming either invasive or dominating. One of the most desirable traits of Salvia coccinea for most gardeners is the plant's ability to attract hummingbirds and butterflies. This scarlet sage's sweet nectar should fill your garden with hummingbirds throughout the summer.