Ageratum houstonianum Blue Horizon F1 | Floss Flower Seeds

Ageratum Blue Horizon F1 is a tall floss flower with fluffy, purplish-blue flower clusters and strong stems for cutting. This vigorous triploid F1 hybrid develops numerous branches and larger flower clusters than traditional bedding ageratum, making it a productive choice for cut flower gardens.

Growing approximately 75–76 cm tall, Blue Horizon adds soft colour and texture to summer borders and bouquets. Its blue-violet flowers combine beautifully with white, blush pink, apricot and soft yellow blooms.

Plant Information

Botanical Name: Ageratum houstonianum
Common Name: Floss flower
Variety: Blue Horizon F1
Plant Type: Annual
Flower Colour: Purplish blue
Height: Approximately 75–76 cm
Habit: Upright, vigorous and branching
Position: Full sun
Soil: Fertile, well-drained soil
Time to Flower / First Harvest: Approximately 12–15 weeks from sowing under suitable conditions
Uses: Cut flowers, mixed borders and larger containers

A Tall Ageratum for Cut Flowers

Blue Horizon F1 offers the familiar soft texture of ageratum on longer, sturdier stems. Its branching habit produces numerous flowering stems, providing useful material for mixed bouquets and floral arrangements.

This is a tall variety, so allow room for its growth when planting in borders or containers. Support netting helps keep stems upright in a cutting bed.

Sowing & Germination

Sowing Method: Start indoors for transplanting
Sowing Depth: Surface sow; light is required for germination
Germination Temperature: Approximately 25°C
Germination Time: Around 7 days under suitable conditions
Seedling Production: Approximately 5 weeks

Sow onto the surface of a fine, moist, well-drained seed compost and gently press into place. Do not bury the seeds. A very light covering of coarse vermiculite may be used, provided light can still reach them.

After emergence, provide bright light and good air circulation. Reduce the temperature to approximately 16–21°C and keep the compost moist without waterlogging. Transplant promptly once the seedlings are ready. Harden off before planting outdoors after the risk of frost has passed.

Spacing & Pinching

Choose the growing method to suit your cutting needs:

• Single-stem production: Space approximately 10 × 10 cm apart, provide support netting and do not pinch.
• Multiple-stem production: Space approximately 20 × 20 cm apart and pinch the growing tip to encourage side shoots and more flowering stems.

Growing & Care

Plant in full sun and well-drained soil. Water regularly, particularly while plants establish and during dry weather. Severe drying can cause yellow leaves or reddish leaf edges.

Feed moderately. Excess nitrogen encourages overly soft growth and can reduce vase performance. Maintain airflow around the plants and avoid prolonged wetting of the foliage.

Blue Horizon is a facultative long-day plant: longer days encourage flowering. In professional production, supplementary lighting during short days can help improve stem length and flower quality.

Flowering & Harvest

Allow approximately 12 weeks from sowing for summer production and around 15 weeks for winter production under controlled conditions. Outdoor flowering time varies with sowing date, temperature and available light.

Cut when the flower clusters are well coloured. Place stems promptly into clean water and remove any foliage below the waterline. Blue Horizon’s lasting flowers and soft texture make it a useful addition to summer bouquets.