Space seeds about 6 inches apart, then when first true leaves appear, thin to about 60 cm (2′) apart.
Plant in a shallow trench 2.5-5 cm (1-2″) deep.
Prefers well-drained dry or moist soil, but will grow in light (sandy), medium (loamy) and heavy (clay) soils. pH 6.0 to 7.5. Can grow in semi-shade, but full sunlight is best. Can tolerate drought.
Seeds will sprout in 7-10 days.
Sow seeds directly into the soil after all danger of spring frost is past.
Water regularly during their most important growth period (about 20 days before and after flowering). Deep, regular watering helps encourage root growth, important for supporting big top-heavy blooms.