The "Blue Diddley" Vitex, scientifically known as Vitex agnus-castus 'PIIVAC-III', is a cultivar of Vitex, also known as Chaste Tree or Monk's Pepper. Here are some key features of the "Blue Diddley" Vitex:

1. Appearance: The "Blue Diddley" Vitex is a deciduous shrub or small tree that typically grows to a height and width of about 3 to 6 feet. It has a rounded, spreading growth habit with aromatic, gray-green foliage.

2. Flowers: One of the most notable features of the "Blue Diddley" Vitex is its long, showy spikes of fragrant, lavender-blue flowers. These flowers appear in summer, attracting bees, butterflies, and other pollinators to the garden. The bloom period can last for several weeks, providing a colorful display.

3. Fruit: After flowering, the "Blue Diddley" Vitex may produce small, dark purple to black berries. These berries are not typically used for culinary purposes but are attractive to birds.

4. Hardiness: The "Blue Diddley" Vitex is hardy in USDA zones 6-10, making it suitable for a wide range of climates. It is tolerant of heat, drought, and a variety of soil types.

5. Sunlight: This shrub thrives in full sun, where it will produce the best flower display. However, it can also tolerate partial shade.

6. Soil: The "Blue Diddley" Vitex prefers well-drained soil but is adaptable to a variety of soil types, including sandy or clay soils.

7. Landscape Use: The "Blue Diddley" Vitex is often used as a specimen plant in mixed borders, as a focal point in the landscape, or in cottage gardens. It can also be planted in groups or used as a hedge or screen. Additionally, it is suitable for coastal gardens due to its tolerance of salt spray.

8. Maintenance: The "Blue Diddley" Vitex is relatively low-maintenance. It benefits from regular watering during the first growing season to establish a strong root system. Once established, it is drought-tolerant and requires minimal watering. Pruning can be done in late winter or early spring to maintain shape and remove any dead or damaged wood.

Overall, the "Blue Diddley" Vitex is prized for its fragrant flowers, attractive foliage, and ease of care, making it a popular choice for gardens and landscapes.