Caryopteris × clandonensis 'Longwood Blue' is a cultivar of bluebeard, also known as blue mist spirea or Caryopteris. It is a deciduous shrub valued for its late-season bloom, attractive silvery-green foliage, and ability to attract butterflies. Here are some key features and care tips for Caryopteris 'Longwood Blue':

1. Flowers: 'Longwood Blue' produces clusters of small, tubular, lavender-blue flowers. The blooms appear in late summer to early fall, providing a burst of color when many other plants are finished flowering.

2. Foliage: The foliage of 'Longwood Blue' is aromatic and has a silvery-green color. The leaves are lance-shaped and create an appealing contrast with the colorful flowers.

3. Size: This cultivar typically grows to a height of about 3 to 4 feet, with a similar spread. It has a mounded and compact growth habit.

4. Sunlight Requirements: Caryopteris 'Longwood Blue' thrives in full sun. Ensure it receives at least 6-8 hours of direct sunlight per day for optimal flowering and foliage development.

5. Soil Conditions: Well-draining soil is essential for bluebeard. While it is adaptable to various soil types, it prefers moderately fertile, well-drained soil. Adding organic matter to the soil can enhance its structure.

6. Watering: Bluebeard is relatively drought-tolerant once established, but regular watering is beneficial, especially during dry periods. Avoid overwatering to prevent waterlogged conditions.

7. Pruning: Pruning is typically done in late winter or early spring to encourage a more compact and bushy shape. You can also deadhead (remove spent flowers) to promote additional blooms.

8. Hardiness: 'Longwood Blue' is generally hardy in USDA Zones 5 to 9, but its specific cold tolerance can vary. Provide winter protection, such as a layer of mulch, in colder climates.

9. Landscape Use: Caryopteris 'Longwood Blue' is often used in mixed borders, foundation plantings, or as a low hedge. It pairs well with other late-season bloomers and adds a touch of color to the garden in the fall.

10. Attracting Pollinators: Bluebeard plants, including 'Longwood Blue,' are known for attracting butterflies and other pollinators with their nectar-rich flowers.

Caryopteris 'Longwood Blue' is a popular choice for gardeners looking to extend the flowering season into the fall. Its compact size and attractive foliage make it a versatile and eye-catching addition to various garden settings. Always consider local growing conditions and consult with local nurseries for the most accurate care information.