How to Grow Larkspur Seeds

Grow Guide #2280
Family: Ranunculaceae
Binomial name: Consolida regalis
Life Cycle: Annual

This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Larkspur (Consolida regalis).

When to Sow Larkspur Seeds

Use the table below to identify the best time of year to sow larkspur seeds in your climate.

  JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Cool
Temperate
Sub-Tropical
Tropical
Arid

Preparation

Larkspur plants are best grown in full sun or part shade. Choose a location that will receive at least 3 hours of full sun each day.

Larkspur plants commonly self-seed in the garden. Self-seeding plants drop seeds onto the soil at the end of the season that may germinate and grow without help the following season. Choose a position where new plants will be welcome. If you do not want larkspur to become established in your garden, deadhead plants before they can drop seed or grow them in containers.

Larkspur plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.

How to Sow Larkspur Seeds

Optional: Stratifying seeds prior to planting may improve the speed and success of germination. Stratification involves exposing the seeds to a period of cold temperature which for some species helps to break dormancy and spur the seeds to germinate. Read more about stratification here.

Larkspur seeds grow best when they are sown directly into the garden.

  1. Sow seeds directly in the garden 3mm deep and 20cm apart.
  2. Keep soil moist but never wet or dry.
  3. Seeds should germinate in around 14-21 days at a soil temperature of 12-18°C.
  4. Young seedlings will need protection from pests, pets and weather until they are established.

How to Grow Larkspur

Larkspur plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. Learn more about watering here.

If soil was well prepared no extra fertiliser should be necessary. In poor soil or to give your plants an extra boost, application of a high-potassium fertiliser or one formulated for flowering plants can be beneficial:

  • Apply slow release fertiliser at the recommended rate when transplanting or when seedlings are 5-10cm tall.
  • Apply liquid fertiliser at the recommended rate and frequency while plants are fruiting or flowering.

Larkspur plants may need to be supported as they grow. Depending on the expected size and height of the plant, use a stake, bamboo cane, trellis or string lines to support plants. Make sure you have the support in place when you sow seed or transplant seedlings to avoid disturbing the plant's roots later.

Larkspur plants should flower in approximately 130-150 days.

If growing larkspur for cut flowers, use sharp snips or secateurs to cut the longest stems possible, removing the lower leaves and placing the stems immediately in a clean bucket of water. Learn more about cutting and conditioning homegrown flowers here.

Deadhead larkspur flowers regularly during the growing season. Using sharp secateurs or snips cut fading or dead flowers off just above a set of leaves. Removing old flowers regularly will encourage plants to produce more flowers. Learn more about deadheading flowering plants here.

Common Problems when Growing Larkspur

Like all plants, larkspur is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing larkspur plants:

  • Aphids
    Aphids are small (2-4mm long) sap-sucking insects that congregate on the new shoots or the undersides of leaves. They can cause leaves to wilt or become discoloured, and also excrete honeydew which can attract ants and other insect pests. To manage aphids, remove them by spraying with a garden hose, apply a soap or alcohol spray, or encourage predatory insects to your garden. Read more about aphids here.
  • Powdery Mildew
    Powdery mildew is caused by fungal spores reproducing on the leaves of plants. First showing as white spots on leaves, affected areas can spread quickly to cover the entire leaf surface. While rarely fatal, powdery mildew can reduce yields. Water plants at soil level (not on leaves) to prevent spreading spores, allow good air flow between plants, remove affected leaves and if necessary spray with an appropriate fungicide or homemade spray. Read more here about powdery mildew here.
  • Slugs and Snails
    Slugs and snails are molluscs that feed on tender leaves and shoots, mostly at night, leaving slimy trails behind them. Control them by removing their hiding places, keeping free range poultry, collecting them by torchlight or by placing traps. Read more about slugs and snails here.

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