Heucherella is a successful hybrid cross between two North American natives: Heuchera (Coral Bells) and Tiarella (Foamflower). This hybridization combines the vibrant, multi-hued foliage of Heuchera with the increased hardiness and vigor of Tiarella. The result is a resilient perennial, and ‘Stoplight’ is a highly regarded cultivar known for its dramatic, season-long color display. It is valued primarily as a mounding foliage plant, bringing a bright, consistent presence to shaded garden spaces.
The Distinctive ‘Stoplight’ Foliage
The cultivar ‘Stoplight’ earns its name from its striking, two-toned color pattern. In spring, newly emerging leaves display a bright chartreuse to shocking-yellow base color, sharply contrasted by a prominent, dark red or burgundy pattern centered along the main veins. This creates a vibrant, eye-catching effect, with the intense yellow-green acting as a luminous backdrop for the dark central markings.
As the season progresses and temperatures increase, the leaf color matures and softens. The shocking-yellow base transitions to a lime green or straw-yellow hue, though the central red veining remains distinct. This seasonal shift ensures continuous interest throughout the year. The plant establishes a compact, mounding habit, typically reaching 6 inches high and 14 inches wide. While the foliage is the primary attraction, it produces airy sprays of tiny white, bell-shaped flowers in late spring to early summer, rising up to 16 inches above the foliage.
Optimal Planting Conditions
‘Stoplight’ performs best in partial shade, receiving bright, indirect light, such as morning sun followed by afternoon shade or all-day dappled sunlight. Too much direct, intense afternoon sun, especially in warmer climates, can cause the foliage to wilt, fade, or scorch. Conversely, planting in deep shade reduces the intensity of the yellow and lime colors, resulting in a less vibrant display.
The soil must be rich in organic matter and consistently well-draining. While these plants require average, consistent moisture, they are extremely susceptible to crown rot if the soil remains waterlogged. To prevent this issue, avoid burying the plant’s crown—the point where the stems meet the roots—when planting. ‘Stoplight’ is reliably hardy, thriving in USDA Hardiness Zones 4 through 9.
Routine Care and Longevity
Once established, ‘Stoplight’ requires consistent moisture, especially during dry periods, but the soil must never become saturated. A layer of organic mulch helps retain soil moisture and regulate temperature. Fertilization should be minimal; incorporating organic material into the soil at planting is usually sufficient. Excessive feeding can lead to weak, overly lush growth susceptible to fungal issues.
A yearly spring clean-up is recommended to remove any dead or damaged semi-evergreen foliage before new growth begins. This species is prone to “heaving,” where winter freeze-thaw cycles push the plant’s crown out of the soil. If heaving occurs, gently push the crown back into the soil and mulch to protect the exposed roots. To maintain vigor and prevent the center from becoming woody, division is necessary every three to five years. Division is best done in early spring by cutting the clump into smaller sections, ensuring each piece has a healthy root mass and several shoots.