The short answer

Quick Answer

Delphinium thrives in full sun on loamy soils (pH 6-7.5), free-draining. Reaches 1.2 to 2m tall in flower, 60cm spread. Hardy to around -30°C.

Read on for pruning, planting, companions, seasonal care and common problems.

On this page

Pruning

When: After first flower spike fades. Cut back in autumn

How: Cut spent flower spikes to ground level for a second flush in late summer. Cut all growth to ground in November

Origin, history and folklore

Origin: Northern hemisphere, mostly Europe and Asia

Native or exotic: Exotic. Some species native to UK chalk downland

History: Bred extensively in Britain since the 1800s. The Pacific hybrids were developed in the 1930s and the English hybrid strains remain world famous

Folklore: In Greek myth, delphiniums sprang from the blood of Ajax, who fell on his sword in shame

Fun fact: The name delphinium comes from the Greek for dolphin, because the flower buds were thought to resemble a dolphin's nose

Historical medicinal uses: All parts toxic. Used historically as a lice treatment. Not for self-medication

Wildlife and biodiversity

Pollinators: Bees and butterflies. Bumblebees visit for nectar [4][5]

Pollinator ranking: 7 out of 10 (10 means a lot of pollinators, 1 means little) [4][5]

Biodiversity value: 6 out of 10 Medium. Provides nectar for bees[3][4][5][13]

Seasonal highlight: 7 out of 10 Flower spires June to July, repeat September[4]

Companion planting and pests

Companion planting: Classic with roses, lupins and peonies in cottage borders

Pest control: Slugs and snails love new shoots in spring. Protect with organic pellets

Common diseases and issues: Crown rot, powdery mildew, delphinium black blotch. See RHS Delphinium page

Invasive note: Not invasive

CGM care note

Delphiniums must be staked before the flower spikes grow tall. We use brushwood or link stakes in April and feed fortnightly with tomato feed once the spikes start to rise.

CGM guides mentioning Delphinium

These articles from our Gardening Knowledge library mention Delphinium and may be useful if you are researching or growing this plant.

Useful resources

Plant relationships, Delphinium

How Delphinium fits with other plants in a real Chiltern garden, what it works well with, what to avoid, and what to use instead in tricky spots.

Works well with

  • Agapanthus (African Lily), shares similar growing conditions, soil, light and drainage needs overlap
  • Beech, shares similar growing conditions, soil, light and drainage needs overlap
  • Echinacea (Coneflower), shares similar growing conditions, soil, light and drainage needs overlap
  • Lavender, shares similar growing conditions, soil, light and drainage needs overlap
  • Pennisetum (Fountain Grass), shares similar growing conditions, soil, light and drainage needs overlap
  • Rosemary, shares similar growing conditions, soil, light and drainage needs overlap

Avoid planting beside

Similar alternatives

Better choice for exposed sites

Better choice for shade

Replacement for failed box

If box blight has hit your hedges, these are the alternatives we recommend:

Seasonal succession partners

Plants with non-overlapping flowering windows to extend the season:

Relevant services

Related articles

Local projects using this plant

See our portfolio for real gardens where we've used Delphinium.

Chiltern growing year

12-month care calendar

Use this as a seasonal prompt for this plant. Exact timing depends on species, exposure, soil moisture and the weather in your garden.

JanuaryCheck winter damage and protect vulnerable new growth.
FebruaryPrune only where the plant and weather allow; plan spring work.
MarchRemove winter debris, weed carefully and begin feeding where appropriate.
AprilPlant in workable soil and water new plants during dry spells.
MayMulch before the ground dries and watch for pests and new disease.
JuneKeep new planting watered, stake soft growth and deadhead where useful.
JulyWater deeply during dry Chiltern weather and inspect stressed foliage.
AugustMaintain moisture, remove damaged growth and prune only after flowering when suitable.
SeptemberA good month for planting, dividing and preparing soil for autumn work.
OctoberPlant hardy stock, clear diseased material and add a measured mulch.
NovemberFinish planting before hard frost and check ties, stakes and drainage.
DecemberReview the year, protect exposed plants and plan the next season.

References and justification

The values above for Delphinium are supported by the following academic and horticultural authorities. Each reference lists the variables it underpins and the basis for the rating. Inline citation markers (e.g. [4]) next to each value link directly to the supporting reference below.

  1. 1
    RHS (2024). Delphinium (Delphinium elatum and hybrids). Plant Profile. Royal Horticultural Society.

    Confirms the horticultural values above for light, temperature (RHS hardiness rating), water, soil type, pH, drainage, feeding, and pruning times/method for Delphinium. The RHS is the UK's leading horticultural charity and its plant database is the authoritative reference for garden-worthy species in the British Isles.

  2. 2
    Kew Science (2024). Delphinium elatum and hybrids. Plants of the World Online. Royal Botanic Gardens, Kew.

    Confirms the botanical classification (family Ranunculaceae), native geographic origin, and native/exotic status listed above. Kew's POWO is the globally recognised taxonomic authority for vascular plants, maintained by the Royal Botanic Gardens, Kew.

  3. 3
    Wang W, Liu Y, Yu SX, et al. (2014). Ranunculaceae phylogeny and evolution. Journal of Systematics and Evolution, 52(2), 161-174.

    Peer-reviewed phylogenetic/taxonomic study of Ranunculaceae confirming the origin, taxonomy, and ecological characteristics listed above. Supports: origin, taxonomy, biodiversity_value.

  4. 4
    Garbuzov M, Ratnieks FLW (2014). Quantifying variation among garden plants in attractiveness to bees and other flower-visiting insects. Functional Ecology, 28(2), 364-374.

    Supports the Pollinator ranking of 7/10 for Delphinium. The pollinator description above ("Bees and butterflies. Bumblebees visit for nectar") aligns with this study's finding that moderate-ranked plants attract a steady but not exceptional number of flower-visiting insects. The Biodiversity value assessment ("Medium. Provides nectar for bees") reflects the plant's supplementary role in providing nectar during its flowering window (Seasonal highlight: "Flower spires June to July, repeat September"). Plants in the moderate range contribute to garden biodiversity but are not primary pollinator resources.

  5. 5
    British Beekeepers Association (2024). Garden Plants for Bees. BBKA.

    Supports the Pollinator ranking of 7/10 and the Pollinators description ("Bees and butterflies. Bumblebees visit for nectar"). The BBKA maintains the UK's definitive list of pollinator-friendly garden plants, and Delphinium's ranking is consistent with BBKA guidance on bee-attractive species. Also supports the Biodiversity value assessment ("Medium. Provides nectar for bees") in the context of garden-scale pollinator support.

  6. 6
    RHS (2024). Pests and Diseases. Royal Horticultural Society.

    RHS pest and disease database confirms the common diseases, pest control notes, and companion planting observations listed above for Delphinium. The RHS advisory service is the UK's primary source of evidence-based horticultural pest management.

  7. 7
    RHS (2024). RHS Hardiness Ratings. Royal Horticultural Society.

    The RHS hardiness rating system (H1a-H7) underpins the temperature tolerance value given above. Delphinium's rating is consistent with RHS published hardiness data for the Ranunculaceae family.

  8. 8
    RHS (2024). Soil Types and Testing. Royal Horticultural Society.

    RHS soil classification and testing guidance supports the soil type, pH range, and drainage requirements listed above for Delphinium. The RHS advises on soil assessment for all garden plants in the UK.

  9. 9
    GB Non-native Species Secretariat (2024). GB Non-native Species Information Portal.

    The GB Non-native Species Secretariat database confirms the invasive status assessment for Delphinium. This government-backed portal tracks all non-native species in Great Britain and their ecological impact classification.

  10. 10
    RHS (2024). Pruning Guide: Shrubs and Climbers. Royal Horticultural Society.

    RHS pruning methodology and timing guidance for shrubs and perennials underpins the pruning times and methods listed above for Delphinium. The RHS assigns plants to pruning groups (1-13) based on flowering time and growth habit.

  11. 11
    RHS (2024). Watering Plants. Royal Horticultural Society.

    RHS watering advice supports the water requirement and drainage values listed above for Delphinium. The RHS provides evidence-based watering guidance for UK garden conditions.

  12. 12
    RHS (2024). Feeding and Mulching. Royal Horticultural Society.

    RHS feeding and mulching guidance supports the feeding recommendations for Delphinium. The RHS advises on fertiliser application rates and timing for all garden plant types.

  13. 13
    Bentrup G (2008). Agroforestry: Sustaining native bee habitat for crop pollination. USDA Forest Service, Agroforestry Note 32.

    USDA Forest Service research on companion planting for pollinator habitat supports the companion planting and pest control observations listed above for Delphinium. This is a peer-reviewed extension publication on agroforestry and biodiversity.

  14. 14
    Royal Botanic Gardens, Kew (2024). Plants Used in Traditional Medicine. Kew Science.

    Kew Science's research on plants used in traditional medicine supports the historical medicinal uses, folklore, and history entries above for Delphinium. Kew's ethnobotany database is the UK's leading scientific resource on plant use by humans.

Where Delphinium performs well locally

Towns where Delphinium is well suited to typical local soil and climate conditions.

Excellent and strong match

Suitable with preparation

View all areas we cover