Dwarf sunflowers typically grow no taller than 2 feet. Select a 6-inch-diameter pot with an equal depth to provide enough room for the roots and to prevent topheaviness. Pots must contain at least one bottom drainage hole for excess water to drain from the soil. Use a drip tray beneath the pot so the draining water doesn't make a mess indoors. Any type of quality potting soil works well for sunflowers, as long as it is well-aerated and doesn't compact easily. You can plant one nursery seedling per pot or sow a sunflower seed directly in the pot in early spring.
The greatest challenge to indoor growing is providing the sunflower with ample sunlight. Set the pot in a window that receives at least six hours of direct sunlight. The sunflower stem may become weak and leggy if the plant is constantly reaching toward the sunlight. Providing enough light and rotating the pot every two to three days so the flower receives sunlight on all sides prevents legginess. An indoor temperature that remains near 72 degrees during the day and up to 7 degrees cooler at night provides sufficient warmth for compact growth.
Keep the soil moist at all times, but avoid overwatering and soggy soil. Indoor plants generally require watering every three to five days, or when the top inch of soil begins to feel dry. Empty the drip tray underneath the pot after each watering so that the soil doesn't reabsorb the drained water. When watering, avoid wetting the foliage. Wet leaves are more prone to fungal and bacterial infections, especially in the cooler and lower-light conditions inside the home. Water the plants at the base, so that the moisture soaks quickly into the soil instead of sitting on leaf surfaces.
Pot-grown sunflowers need regular fertilization to replenish the nutrients in the soil as the flower uses them. A soluble fertilizer formulated for flowering plants, such as a 15-5-15 ratio blend, works well for most dwarf sunflower varieties. Apply the fertilizer every two weeks at half the rate recommended on the fertilizer label for the pot size. Stop all fertilizer application once the flower buds begin to swell. Fertilizing during the blooming period causes the flowers to decline more quickly.