Helianthus annuus for pot production
Life cycle: Annual
Family, Origin: Asteraceae, North America
Exposure: Full sun
Garden height: 30-50 cm
Crop time: Plug crop: 3-4 weeks
Flowering pots: 8-10 weeks, depending on light intensity and variety
Uses: Plants for bedding, attractive pot plants and container plants for patio.
Available as: Raw Seed and Fungicide treated Seed, 15-50 s/g
Sowing method: 1-2 seeds per plug, can be sown directly into final pot
Sowing time: March-End July, sowing in intervals
Germination*: 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.
Plug culture: From Stage II reduce the soil moisture, but the plug should not dry out.
The temperatures should not be below 12 °C, because low temperatures are a cause for poor and slow germination and for yellow edged leaves
(iron-deficiency) as well as the inhibition of shoot branching. 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 immediately after germination is recommended.
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 3-4 weeks after germination transplant 1 plant into a pot (9-13 cm), 3 plants into a bigger pot (20 cm) or into a container (3-5 l).
Media: 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: Short day plant. Keep light levels high. For the flowering Helianthus needs short day (maximum 13 h) and a 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 colour is visible.
Temperature: Grow at 15-18 °C. Cultivate flowering plants not below 12 °C. Helianthus plants do not tolerate frost.
Fertilization: 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.
Cultural hints: Keep optimal cultivation conditions, then Helianthus is an easy and quick pot culture. Avoid water stress situation that can cause yellowing of leaves.
Helianthus responds well to temperature strategies (“Cool Morning” and “Neg. Diff.”).