Let us delve into the world of Lithodora, focusing on the popular cultivar 'Grace Ward'. These plants are beloved for their intense blue flowers and low-growing habit.

What Makes Lithodora diffusa 'Grace Ward' So Special

• Intense Blue Flowers: The most striking feature of 'Grace Ward' is its profusion of small, star-shaped flowers in a vibrant, true blue color. This blue is exceptionally intense and eye-catching, making it a standout in the garden.
• Long Bloom Time: 'Grace Ward' blooms for an extended period, typically starting in late spring and continuing through summer, often with sporadic reblooming into fall.
• Low-Growing, Spreading Habit: It forms a low, spreading mat of evergreen foliage, making it an excellent ground cover or rock garden plant.
• Evergreen Foliage: The small, dark green, needle-like leaves provide year-round interest, even when the plant is not in bloom.
• Well-behaved: Unlike some other ground covers, 'Grace Ward' is not aggressively invasive. It spreads slowly and is relatively easy to control.

Description and Details

• Growth Habit: Low-growing, spreading, evergreen sub-shrub (a small, woody-based plant).
• Stems: Wiry, trailing stems that root at the nodes where they touch the ground.
• Leaves: Small (about 1/2 to 1 inch long), narrow, linear to lanceolate, dark green, and slightly hairy. The leaves are arranged alternately on the stems.
• Flowers: Small (about 1/2 inch across), star-shaped, five-petaled, and a brilliant, gentian blue. The flowers are borne in clusters at the tips of the stems.
• Fruit: Small, nut-like fruits (nutlets).
• Size: Typically grows to 6-12 inches tall and spreads to 1-2 feet wide (or more over time).

Native Habitat (of Lithodora diffusa)

• Origin: Lithodora diffusa is native to southwestern Europe, particularly Spain, Portugal, and France. 'Grace Ward' is a selected cultivar of this species.
• Typical Habitats: Found in rocky, well-drained areas, often in open woodlands or scrublands. It prefers acidic soil.

Landscaping Design Tips

• Rock Gardens: Its low-growing habit, drought tolerance, and preference for well-drained soil make it an ideal choice for rock gardens.
• Ground Cover: Use it as a ground cover in small areas, along pathways, or at the front of borders.
• Edging: Can be used to edge pathways or garden beds.
• Containers: Suitable for containers, where they will spill over the edges.
• Slopes: Can help to stabilize slopes and prevent erosion.
• Mixed Borders: Combine it with other low-growing perennials and shrubs, using its blue flowers to create a striking contrast. Good companions include plants with yellow, white, or pink flowers, or plants with contrasting foliage textures.
• Alpine Gardens: Its natural habitat makes it a good fit for alpine gardens.

Planting and Care

• Planting:
• Timing: Plant in spring or fall.
• Spacing: Space plants 12-18 inches apart.
• Soil: Crucially, Lithodora needs acidic soil (pH 5.0-6.5). It will not thrive in alkaline soil. The soil must also be well-drained. Amend heavy clay soils with plenty of organic matter (like compost, peat moss, or aged pine bark) to improve drainage and acidity.
• Light: Prefers full sun to partial shade. In hotter climates, it will benefit from some afternoon shade.
• Care:
• Watering: Water regularly during the first growing season to establish a deep root system. Once established, it is relatively drought-tolerant, but it will perform best with consistent moisture, especially during dry periods. Avoid overwatering, which can lead to root rot.
• Fertilizing: Generally, does not require much fertilization. If needed, use an acid-forming fertilizer (like those formulated for azaleas and rhododendrons) in early spring.
• Mulching: Apply a layer of acidic mulch, like pine needles.
• Pruning: Prune lightly after flowering to maintain a neat shape and encourage bushier growth. You can also remove any dead or damaged stems.
• Pest and Diseases: Generally, pest and disease resistant. Root rot can be a problem in poorly drained soils. Spider mites can sometimes be an issue in hot, dry conditions.
• Winter Care: May benefit from winter protection (mulch) in colder climates.

Taxonomy

• Kingdom: Plantae
• Phylum: Tracheophyta
• Class: Magnoliopsida
• Order: Boraginales
• Family: Boraginaceae (Borage family)
• Genus: Lithodora
• Species: Lithodora diffusa
• Cultivar: 'Grace Ward'

Morphology

• Root System: Fibrous root system.
• Stems: Wiry, trailing stems.
• Leaves: Small, narrow, linear to lanceolate, dark green, and slightly hairy.
• Flowers: Star-shaped, five-petaled, and a brilliant blue. The flowers have a small, white throat.
• Fruit: Small, nut-like fruits (nutlets).

Other Insights for Gardeners

• Soil pH is Critical: The most important factor for success with Lithodora is acidic soil. If your soil is alkaline, you will need to amend it regularly with acidifying materials or consider growing it in a container with an acidic potting mix.
• 'Heavenly Blue': Another popular cultivar is 'Heavenly Blue', which is very similar to 'Grace Ward'.
• Propagation: Lithodora can be propagated by cuttings taken in summer, or by layering. Division is possible, but it can be difficult due to the plant's woody base.
• Longevity: Can be short lived, so propagation is useful.
• Deer and Rabbit Resistance: Generally resistant.

In conclusion, Lithodora diffusa 'Grace Ward' is a beautiful and rewarding plant for gardeners who can provide the right conditions, especially acidic, well-drained soil. Its intense blue flowers, evergreen foliage, and low-growing habit make it a valuable addition to rock gardens, borders, and containers. With proper care, this plant will provide a stunning display of blue for many years.