Louisiana Super Plants: Diamonds Blue Delphinium

Maureen Thiessen, Edwards, Ashley, Abdi, Damon, Fields, Jeb S.

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Diamonds Blue Delphinium (Delphinium chinensis)

  • Recommended Use: Cool-season bedding plant, great for borders, cut flowers and bouquets.
  • Exposure: Full sun to part sun
  • Size: Up to 16 inches tall, 10 to 12 inches wide
  • Habit: Upright
  • Bloom Time: Fall through spring
  • Maintenance Category: Low
  • Water Use: Moderate
  • Highlights: This cold-hardy plant provides cool-season color, fine textured foliage, and striking


Another common northern climate perennial, delphiniums are typically strangers in the Deep South. Diamonds Blue, however, is a Delphinium chinensis variety that grows lower and bushier than its tall northern cousins. It grows more vigorously than typical delphinium and is capable of blooming over a longer duration. This cool-colored and cold-hardy plant can add interest to the garden throughout Louisiana winters. The intense blue bloom color the flowers provide is seldom seen in the market, making this plant a fantastic option for adding an uncommon color to the cool-season garden. Their short stature can steal the show as a foreground plant or provide a blue backdrop behind other low-growing, cool-season favorites such as violas, lobelia and alyssum.

The foliage of Diamonds Blue delphinium is finely divided, adding a delicate, lacy texture to the garden. The flowers emerge from tall spikes, often growing up to 16 inches tall. Each flower contains five electric-blue petals, each spotted with a dab of purple. Mass plantings can create giant swaths of blue in the garden, adding a calming color to the landscape.

Transplant Diamonds Blue delphinium anytime from October through March into beds prepared with plenty of organic matter. With its compact size, Diamonds Blue is also a great choice for container plantings. Early fall is the best time to plant, particularly if a showy spring arrangement is desired. This plant has very few pest and disease problems and is generally considered a low maintenance option in the landscape. Once the flowers fade, deadheading the spikes encourages repeat blooms throughout the season. The flower spikes also make excellent cut flowers and add some vertical variety to bouquets and arrangements. During trials at the Hammond Research Station, Diamonds Blue provided excellent color until early June.


  • Plant in a sunny to partly shady location with excellent drainage.
  • Work organic matter into the upper 2 inches of the soil prior to planting.
  • Ideal soil pH is slightly acidic, between 6.0 to 6.5.
  • Space plants 12 inches apart.
  • Plant from October to March.

Growth Habit

  • Mounding, lacy foliage with tall upright bloom spikes.
  • Up to 16 inches tall and 10 to 12 inches wide.

Care and Maintenance

  • Fertilize with general purpose fertilizer at planting and provide monthly follow up applications or use a slow-release fertilizer at planting to provide long-term nutrition.
  • Remove faded flower spikes to encourage more bloom production.
  • Cold hardy throughout Louisiana, adding interest in the cool season.
  • Remove in early summer or when plants succumb to heat.

Diamonds blue delphiniums bushes.

Diamonds Blue delphiniums do well in sunny to partly shady locations. LSU AgCenter file photo

Diamonds blue delphiniums bushes.

The flower spikes of Diamonds Blue delphiniums make excellent cut flowers.

Close-up view of diamonds blue delphiniums.

Large plantings of Diamonds Blue delphinium can create giant swaths of blue in the garden. LSU AgCenter file photos

3/16/2023 3:59:19 PM
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