Glandora prostrata is a popular choice for gardens, known for its vibrant blue flowers and prostrate, spreading growth habit. It forms a lush carpet of foliage, adding both color and texture to various garden designs.
Glandora Prostrata Overview
Glandora prostrata, also known as Creeping Glandora, Shrubby Gromwell, or Purple Gromwell, is a subshrub in the Boraginaceae family. Native to temperate southwestern Europe (Portugal, Spain, and France), it forms a dense, evergreen groundcover.
Its foliage features small, lance-shaped leaves, typically mid- to dark green and slightly hairy. From late spring to early summer, it produces abundant, vivid deep blue flowers, which are star-shaped or funnel-shaped with five lobes, measuring 12 to 15 millimeters wide. Mature plants reach 15 to 20 centimeters tall and spread up to 60 centimeters.
Optimal Growing Environment
Glandora prostrata prefers full sun for abundant flowering, though it tolerates partial shade. A south or west-facing aspect maximizes light. Good air circulation helps prevent fungal issues.
The plant thrives in well-drained, acidic to neutral soil (pH 5.0-6.5). Loamy or sandy soil is well-suited, facilitating quick drainage and preventing waterlogging. Incorporating humus enhances soil structure and fertility.
It performs best in temperate regions, hardy to USDA Zone 7, with some varieties tolerating down to Zone 5-6 (-15 to -10 degrees Celsius). Protection from extreme cold and harsh winds benefits young or newly established plants.
Planting and Maintenance
Plant Glandora prostrata during its active growing season for proper establishment. Prepare the site by loosening the soil and amending it with organic compost or grit if drainage needs improvement. Ensure the planting hole is twice as wide as the root ball and slightly shallower, with the root ball’s top marginally above ground level. After placing the plant, backfill, gently firm, and water thoroughly to settle the soil.
Keep the soil consistently moist but not saturated from mid-spring through mid-autumn. Allow the soil surface to dry out slightly between waterings to prevent root issues. Once established, the plant exhibits some drought tolerance, but regular watering during prolonged dry periods supports its health and flowering. During winter, especially for container-grown plants, reduce watering significantly.
Glandora prostrata has low nutrient requirements, but a light fertilizer application can enhance performance. If needed, use a balanced fertilizer (e.g., 5-10-10) or one for acid-loving plants. Apply during the growing season, every four to six weeks, at a 50% diluted strength for liquid feeds.
Pruning is minimal but beneficial for maintaining shape and promoting denser growth. A light trim after the main flowering period (late spring to early summer) removes spent blossoms and encourages bushiness. In temperate zones, early spring pruning before new growth is suitable; avoid late fall pruning to preserve winter hardiness. Remove any dead or damaged stems as observed.
Garden Applications
Glandora prostrata excels as a vibrant groundcover, forming a dense, mat-like carpet of evergreen foliage and brilliant blue flowers. Its low-growing, spreading habit effectively covers large areas, suppresses weeds, and provides continuous color.
Its preference for well-drained conditions and prostrate nature makes it an excellent choice for rock gardens, where it cascades over stones and fills crevices. Its trailing stems create a striking visual when spilling over retaining walls, raised beds, or container edges. This cascading effect adds dynamic movement and softens hard landscape elements.
It can also be used as a border plant or for edging pathways, providing a defined line of intense blue. Suitable companion plants include species thriving in acidic, well-drained soil that complement its blue hues, such as heather, Alchemilla, Dianthus, or Veronica.
Addressing Common Issues
Yellowing leaves (chlorosis) often indicate high soil pH and iron deficiency. Acidifying the soil with appropriate amendments can help correct this problem.
Poor flowering might result from insufficient sunlight exposure or an imbalance of nutrients in the soil.
Root rot is a significant concern, almost always caused by inadequate drainage or consistent overwatering. Ensuring the plant is in well-drained soil and avoiding waterlogged conditions are the primary preventative measures.
If the plant exhibits leggy growth, it may be reaching for more light, suggesting a need for increased sun exposure or light pruning to encourage denser branching. Glandora prostrata is generally resistant to most common pests and diseases. However, it can occasionally be susceptible to general garden pests or fungal issues in overly humid or poorly ventilated environments.