How to Grow Larkspur (Delphinium consolida)

How to Grow Larkspur (Delphinium consolida)

The birth-flower of July, larkspur (Delphinium consolida) is most often grown as an annual. It is a staple in any cottage garden, both on its own and planted with other flowers. As an annual, larkspur will readily self-seed, coming back year after year.

Continue reading to learn how to grow and care for these beauties!

Larkspur basic details

  • Plant type: Annual
  • Difficulty: Easy; low maintenance
  • Light: Part Sun, Sun
  • Height at maturity: 30-90 cm (1-3 feet, depending on the variety)
  • Spread at maturity: 15-45 cm (6-18 inches, depending on the variety)
  • Bloom time: Spring to summer
  • Features: Cut flowers, good for containers
  • Common names: Line flower, Knight's-Spur

Larkspur are an easy to grow and unfussy plant, but there is still one important factor to take into consideration: these seeds must go through a cold period in order to germinate. In most places, this means that you should sow the seeds directly in the ground in the fall.  

If it does regularly stay colder than 18 C (64 F) during the winter, they will not grow! 

In warmer climates, the best way to ensure a cold spell is to pop them in the fridge in an airtight plastic bag for two weeks before planting. Once planted, the seeds should germinate within three weeks.

How to start larkspur seeds

  1. Start with well-draining soil. If planting in pots, make sure there are adequate drainage holes at the bottom.
  2. I reccomend sowing them directly in the ground. This is because their roots do not like to be transplanted. 
  3. Space the seeds around 15-20 cm (6-8 inches) apart.
  4. Lightly top with soil and then level the soil surface. 
  5. Water deeply to encourage root development, but be sure the roots do not stand in water as they risk rot.

Care tips

  • To retain moisture and limit weeds, apply a thin layer of mulch 
  • Water larkspur plants regularly during the summer when rainfall is sparse, as soil should never dry out
  • Deadhead after flowering to encourage rebloom.
  • After the first frost in late autumn, the flowers will turn brown, and you can cut the larkspur back. 
  • Larkspur are happiest in climates with cool and rainy summers. 

Harvesting your larkspur

Larkspur readily self-sow by dropping their seeds. This means that they’ll easily return in the following year. However, to ensure that they don't take over your entire garden, you should harvest the flowers. Plus, this way, you can enjoy their blooms in bouquets!

For the longest vase life cut your larkspur when one-third of the blossoms are open. 

*Safety and toxicity warning

Keep away from pets, lifestock, and children, as, unfortunately despite their beauty, larkspur are poisonus.

If consumed, the plant can cause severe digestive issues, even death. If touched, it can cause severe skin irritation.

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