When to plant Larkspur in Temperate Australia

Temperate zone — applies to Sydney, Melbourne, Adelaide, Perth, Newcastle and similar areas. Growing elsewhere? Cool · Subtropical · Tropical · Arid.

Sow larkspur direct into the ground from February to June, taking advantage of the cool autumn soil that this hardy annual germinates best in. Seed can be slow and erratic, taking 10–21 days, and germinates most reliably when soil temperatures are low, so autumn and early winter sowings outperform spring ones. Sow shallow at just 3 mm and thin to 30–40 cm apart with similar spacing between rows. Larkspur is a long-season crop at around 140 days, flowering the following spring on tall, elegant spikes. In temperate gardens around Melbourne and Adelaide, an autumn sowing rewards you with cottage-garden colour by spring.

Sowing calendar — temperate zone

Green months are your sowing window: February to June.

Growing notes

Larkspur is an annual relative of delphinium, grown for its tall spires of blue, pink and white flowers. In a temperate climate the trick is timing: it germinates best in cool soil and resents transplanting, so sow it direct where it is to grow, in autumn to early winter, rather than raising seedlings in spring.

The most common failure is poor germination from sowing at the wrong time. Warm spring soil and old seed both give patchy, disappointing strikes. The fixes are to sow into cool autumn ground, use fresh seed, and be patient through the 10–21 day germination. Some growers chill seed in the fridge for a week or two before sowing to nudge it along.

Grow larkspur in full sun in well-drained, fertile soil. The tall spikes can flop in wind or after rain, so plant in a slightly sheltered spot or provide light support such as twiggy sticks pushed in among the seedlings while they are young. Thin to the recommended spacing rather than leaving plants crowded, as crowding encourages powdery mildew on the lower leaves in a humid Adelaide or coastal spring.

Leave a few spent spikes to self-seed and larkspur will often return year after year in the same bed.

Larkspur at a glance

Common questions

When is the best time to sow larkspur in temperate Australia?

Autumn to early winter, roughly February to June, gives the cool soil larkspur needs to germinate well. Spring sowings into warm soil germinate poorly, so the cooler months are the reliable window.

Why won't my larkspur seeds germinate?

Larkspur germinates only in cool soil and is slow, taking 10–21 days, so warm-season sowings and old seed both give patchy results. Sow fresh seed into cool autumn ground, and consider chilling seed in the fridge for a week or two first.

Can I transplant larkspur seedlings?

Larkspur dislikes root disturbance and rarely transplants well, so it is best sown direct where it is to grow. Scatter or station-sow into the final bed and thin to 30–40 cm apart.

How do I stop larkspur flopping over?

The tall flower spikes can flop in wind or after rain, so plant in a sheltered spot and push twiggy sticks in among young plants for light support. Avoid crowding, which also weakens stems and invites mildew.

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