Ceratostigma plumbaginoides

Ceratostigma plumbaginoides: The Hardy Blue-flowered Leadwort

Ceratostigma plumbaginoides, also known as Hardy Blue-flowered Leadwort, Hardy Plumbago, Blue Ceratostigma, Plumbago larpentiae, or Ceratostigma larpentiae, belongs to the Plumbaginaceae family of plants. It is native to Western China and is a charming low-growing, mat-forming herbaceous perennial. Known for its hardiness, it can withstand temperatures as low as -10ºC or 14ºF. The plant features red stems and oval leaves, which turn red or purple during the autumn season. Any frost-damaged shoots should be pruned in spring.

Characteristics and Description

Ceratostigma plumbaginoides, commonly called plumbago or leadwort, is a wiry, mat-forming perennial that spreads through rhizomes, creating an attractive ground cover. It typically grows 6-10″ tall with erect stems emerging from the rhizomes. The oval-to obovate leaves, measuring up to 2″ in length, are shiny and medium green, transforming into bronze-red hues during autumn. Throughout the summer to frost bloom period, terminal clusters of 5-petaled, gentian blue flowers, ranging from 1/2 to 3/4″ in diameter, appear above the foliage. These flowers bear a resemblance to those of woodland phlox.

The genus name Ceratostigma derives from the Greek words “keras,” meaning horn, and “stigma,” referring to the horn-like projection on the flower’s stigma. The specific epithet “plumbaginoides” signifies its resemblance to the genus Plumbago.

Ceratostigma plumbaginoides can grow up to 50 cm (20 in) in height. It blooms during late summer and autumn, producing clusters of captivating blue flowers. For optimal growth, plant it in a sunny, sheltered location with moist, fertile, and well-drained soil. Propagation can be achieved through softwood or semi-hardwood cuttings. Although generally pest-free, it is important to watch out for powdery mildew.

This plant can be easily grown in average, medium, and well-drained soils, thriving in full sun to partial shade. It exhibits a wide range of soil tolerance, except for poorly-drained or waterlogged soils. In hot summer climates like St. Louis, it benefits from some afternoon shade. While it may not reliably withstand winter in USDA Zone 5, a light winter mulch can provide additional protection. Given its rhizomatous growth habit, it can become somewhat aggressive under optimal conditions.

Cultivation of Ceratostigma plumbaginoides:

When cultivating Ceratostigma plumbaginoides, consider the following guidelines to ensure successful growth and flourishing:

Sunlight: Ceratostigma plumbaginoides prefers full sun to partial shade for optimal growth and flowering.

Watering: Water the plant regularly, particularly during hot and dry weather. Allow the soil to dry out slightly between waterings to prevent overwatering.

Soil: While Ceratostigma plumbaginoides is not overly particular about soil type, it thrives in well-drained soil. Avoid waterlogged or poorly-drained soil conditions.

Fertilizer: Apply a balanced fertilizer once a year in the spring to provide essential nutrients for healthy growth.

Deadheading: Remove spent flowers by deadheading to encourage continuous blooming and maintain a tidy appearance.

Pruning: In the fall, cut back the plant to approximately 6 inches tall. This will protect it from cold weather and pests during the winter months.

Pests and Diseases: Ceratostigma plumbaginoides is generally not susceptible to major pests or diseases. However, it can be prone to powdery mildew if the leaves remain excessively wet. If powdery mildew occurs, treat it with an appropriate fungicide.

Propagation of Ceratostigma plumbaginoides:

Ceratostigma plumbaginoides can be propagated through various methods:

  • Seed: Sow seeds indoors during winter and transplant the seedlings outdoors in the spring.
  • Cuttings: Take softwood cuttings during the spring or summer. Root the cuttings in a well-draining potting mix.
  • Division: Divide mature plants either in the spring or fall to create new plants.

Additional Tips:

  • Mulch around the base of the plant to retain moisture and suppress weed growth.
  • Ceratostigma plumbaginoides is an excellent choice for borders, rock gardens, or containers.
  • This plant is resistant to deer.
  • Once established, Ceratostigma plumbaginoides exhibits drought tolerance.

By providing proper care and following these guidelines, you can enjoy the beauty of Ceratostigma plumbaginoides in your garden for many years to come.

Ceratostigma plumbaginoides
Blue flowers of Ceratostigma plumbaginoides
Ceratostigma plumbaginoides
Ceratostigma plumbaginoides at Christchurch Greyfriars Church Garden

Also read about Ceratostigma willmotttianum

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