Dictionary of Flowers: Delphinium, Short Varieties

Delphinium short varieties do really well in tubs and containers. Image used under a Creative Commons licence with the kind permission of T.Kiya and Flickr
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Delphinium short varieties do really well in tubs and containers. Image used under a Creative Commons licence with the kind permission of T.Kiya and Flickr

  • Delphinium, Short Varieties
  • Common name: delphinium
  • Family: Ranuculaceae
  • Category: perennial in USDA zone 3-7
  • Height: 10" to 12" and up
  • Width: 12" 
  • Sun/part shade
  • Blooms: early summer to mid-summer
  • Attracts: butterflies, birds
  • Growth: spiky, mounding. Used as a thriller or filler in container combinations
  • Maintenance: medium
  • Soil: fertile, moist, well drained. Water regularly if grown in containers. 
  • Garden uses: containers, mixed border, cottage garden, cut flower garden
  • Diseases: canker, powdery mildew, rust
  • Pests: slugs, snails, thrips, borers, mealybugs

The delphinium genus of plants is composed of over three hundred species of blooming herbaceous perennial plants.

Short species of cultivated delphinium are best suited for containers and front or middle of the mixed or perennial border: delphinium grandiflorum, delphinium cultorum and delphinium belladona and their hybrids are good medium to short varieties.

Taller varieties normally require either stalking or a fence or wall to stand upright and are best planted near the back of a perennial border.

Colors range from white, pinks and carmine, blue and purple.

All parts of the delphinium plant are poisonous to humans and cattle.

Delphiniums require fertile soil and consistent watering. They are heavy feeders, so before planting your delphinium, work some compost and manure into the planting site.

Fertilize through the growing season every two to three weeks. They also prefer alkaline soils, so after checking the soil's pH, adding lime to the ground might be necessary to achieve a range of 6.0 to 7.0.

To maintain the soil moist and keep the roots cool, it helps to mulch around the plant. They need moist soil, but good drainage, so keep a watering schedule during dry summers.

Once they have bloomed, remove spent flowers for a possible second bloom in fall. Apply a top dressing of compost after deadheading to help the second bloom.

Stunning blue Delphiniums. Image used under a Creative Commons licence with the kind permission of Bark and Flickr
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Stunning blue Delphiniums. Image used under a Creative Commons licence with the kind permission of Bark and Flickr

Delphinium can be propagated by seed or division and are readily available at nurseries.

To grow from seed, plant seeds on peat based starting medium, covering them with a thin layer of soil. Place in a dark spot or cover with dark plastic or foil.

Kept at 60 to 70F, seed germinates in two to three weeks. Check for germination and remove dark cover.  

Seedlings need to be kept moist, but not waterlogged. They also require good light, but not direct sunlight. Harden off for two weeks before planting in their permanent position.

Divide plants after three years, in early spring. Plant the divisions straight away in rich soil, being careful not to break roots.




Close-up of purple Delphinium. Image used under a Creative Commons licence with the kind permission of Swallowtail Garden Seeds and Flickr
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Close-up of purple Delphinium. Image used under a Creative Commons licence with the kind permission of Swallowtail Garden Seeds and Flickr

Delphiniums are disease prone. Powdery mildew and rust need to be treated with a fungicide. Canker affected plants should be discarded, no new delphiniums should be planted in the same spot.

Use slug bait to take care of that pest problem and insecticide to clear other pest problems. Delphinium is deer resistant.

Popular varieties:

  • Delphinium grandiflorum 'Summer Nights' - mounding, one foot tall. Bright blue flowers. Short lived variety
  • Delphinium grandiflorum 'Blue Mirror' - two feet plants that bloom all summer. Heat and humidity tolerant. Blue flowers
  • Delphinium nudicaule 'Laurin' - red blooms on dwarf plants, up to fifteen inches tall
  • Delphinium hybrid 'Magic Fountains' - upright variety, up to thirty six inches tall that doesn't require stalking. White, blue and purple blooms
  • Delphinium belladona hybrid ‘Connecticut Yankees’ - thirty inches tall, branching habit. White, blue and purple colored blooms
Bi-color varieties of Delphinium are common and beautiful. Image used under a Creative Commons licence with the kind permission of Pinke and Flickr
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Bi-color varieties of Delphinium are common and beautiful. Image used under a Creative Commons licence with the kind permission of Pinke and Flickr

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