Helianthemum ‘Hartswood Ruby’, commonly known as rock rose or sun rose, is a charming, low-growing evergreen subshrub valued for its vibrant floral display. This mounded perennial features striking ruby-red, saucer-shaped flowers, often with a golden center, that emerge from mid-spring through mid-summer. Its narrow, light green foliage provides a consistent backdrop throughout the year, contributing to its appeal as a garden plant. This particular cultivar is also recognized for its drought tolerance, making it a suitable choice for sunny, arid garden locations.
Growing Conditions
This plant thrives in full sunlight, requiring at least six hours of direct sun exposure daily to produce its abundant blooms. Placing it in a brightly lit area also helps maintain its compact form and prevents leggy growth.
The plant requires well-drained soil and will not tolerate standing water. While it is adaptable to various soil types, including sandy or rocky conditions, it generally performs best in poor to moderately fertile soils. The ideal soil pH for ‘Hartswood Ruby’ ranges from neutral to alkaline, though it can tolerate slightly acidic conditions.
Helianthemum ‘Hartswood Ruby’ needs consistent moisture during its establishment period after planting. Once established, it becomes highly drought-tolerant, necessitating infrequent watering. Overwatering should be strictly avoided, as excess moisture can be detrimental to its health. This sun rose is hardy across USDA Zones 5b through 9b. In colder regions, providing some winter protection may be beneficial.
Care and Maintenance
Pruning is best performed lightly after the main flowering period, typically in mid to late summer. This encourages a tidier plant shape and can promote a second flush of blooms later in the season. When pruning, it is advised to shear back no more than half of the plant’s growth to avoid stressing it.
The plant has low fertilization needs and generally does not require rich soils. If supplemental feeding is deemed necessary, a balanced, slow-release fertilizer can be applied sparingly in the spring. Over-fertilization should be avoided, as it can lead to excessive foliage growth at the expense of flowers.
‘Hartswood Ruby’ exhibits good resistance to most common garden pests and diseases. This inherent hardiness further reduces the need for chemical interventions.
Garden Applications
The versatility of Helianthemum ‘Hartswood Ruby’ makes it suitable for numerous garden designs. Its low, mounding habit and spreading growth make it an excellent choice for rock gardens, alpine troughs, and gravel gardens. It performs well as a ground cover on slopes or along pathways, where its evergreen foliage provides year-round interest.
This sun rose is also effective when mass planted or used as border edging in sunny beds. It can be successfully grown in containers. The vibrant ruby-red flowers attract pollinators such as bees and butterflies. Compatible plants that thrive in similar well-drained, sunny conditions include peonies, digitalis, scabiosa, and hardy geraniums, creating harmonious plant combinations.