Helianthus annuus for cut flower production
Life cycle: Annual
Family, Origin: Asteraceae, North America
Exposure: Full sun
Garden height: 80-160 cm
Crop time: Plug crop: 4-6 weeks
Cut flower production: 10-12 weeks, depending on variety and light intensity
Uses: Plants for bedding, cut flower production
Available as: Raw Seed and Fungicide treated Seed, 17-60 s/g
Sowing method: 1-2 seeds per plug, sowing directly into field is recommended
Sowing time: Indoor forcing: March-August, sowing in intervals
Outdoor forcing: April-Mid July
Germination*: Field: 10-15 days at 15 °C
Stage I: 5-10 days at 21-24 °C,
Stage II: 5-8 days at 18-20 °C,
Stage III and IV: 7-14 days at 15-17 °C,
in media with low soluble salt levels and pH: 5.5-6.2. Cover seed with vermiculite, sand or substrate after sowing. Keep soil slightly moist but not wet.
Field: sow the seeds 3-4 cm deep, protect the seed against birds, mice and slugs.
Plug culture: From Stage II reduce the soil moisture, but the plug should not dry out.
The temperatures should be not below 12 °C, because low temperatures are a cause for bad and slow germination and for yellow edged leaves
(iron-deficiency). Keep short days by darkening for a compact and uniform growth. The short day decreases the cultivation time and the flowering is earlier, too. In early spring supplemental lighting is recommended after germination immediately.
Do not let soluble salt level rise above 0,75 EC. Start fertilization at
50-75 ppm nitrogen in a well balanced formula. During Stage III and Stage IV fertilization levels can be increased to 200-250 ppm.
Growing on Plant cut flowers in 5-30 x 40 cm space.
One stem cultivation: approximately 30-35 plants per m2.
Multiple stem cultivation: approximately 20-25 plants per m2.
Media: Field: Before sowing treat substrate with herbicide or fight the weeds mechanically and fertilize the field. The seeds should develop without any plant concurrence. Standard fertilization: 100-120 g/m2 of a slow release fertilizer.
Greenhouse: Use a well-drained, growing substrate with 15-30 % clay,
1-3 kg/m³ complete balanced fertilizer, 0-2 kg/m³ slow release fertilizer
(3-6 months), iron-chelate, micronutrients, pH: 5.5-6.2.
Photoperiod/Light: Field: Sunny and warm locations.
Greenhouse: Short day plant. Keep light levels high. For the flowering Helianthus need short day (maximum 13 h) and high light intensity.
Keep short days by darkening for a compact and uniform growth. The short day decreases the cultivation time by 3 weeks and the flowering is earlier, too.
In early spring assimilation light is effective for short day. Light deficiency is a cause for shoot stretching and will increase the cultivation time.
The short day can be finished when the bud’s colors are visible.
Temperature: Field: cultivation is possible from April onwards.
Grow at 15-18 °C . Cultivate flowering plants not below 12 °C.
Helianthus plants do not tolerate frost.
Fertilization: Field: N min soil value: approximately 150 g/m2. Avoid high nitrogen levels in soil. Temperatures below 10 °C can be a cause for iron and phosphate deficiency.
Greenhouse: High fertilization levels are required. Fertilize the crop weekly with 200-250 ppm nitrogen, using a potassium balanced fertilizer
(N: K2O-ratio: 1:1,5). Avoid high ammonium and high nitrogen levels.
Prevent magnesium deficiency by applying magnesium sulphate (0,05 %)
1-2 times and in case of iron deficiency apply iron-chelate for 1-2 times.
Cut flowers: Cut flower stems can be harvested, when the flower are at least half open and the petals are just beginning to show colour. Remove the bottom leaves and put the stems in warm water. Vase life: 8-10 days. Cold storage is not recommended. The dried flower production is possible.
Cultural hints: The distance between plants determines the flower diameter. If the space is too close, the branching will decrease and only one shoot will develop. Pinching of the plant tops is possible. The result are at least 2 stems per plant, but the cultivation time increases by 1-2 weeks. Helianthus responds well to temperature strategies (“Cool Morning” and “Neg. Diff.”).
Germination Stages (from seed to finished young plant)
Stage I Starts with the radicle breaking through the testa. The roots are touching the medium. Ends with fully developed cotyledons.
Stage II Starts from fully developed cotyledons. Ends with the fully developed true leaf or true leaf pair.
Stage III Starts from the fully developed true leaf or true leaf pair and ends with 80% of the young plants being marketable.
Stage IV All young plants are ready for sale and in the process of being hardened off. This stage lasts about 7 days.
The cultural recommendations are based on results from trials conducted under Central European conditions. Different conditions in other parts of the world may lead to deviations in results achieved.