How to Care for Sunflowers Inside
The sunflower (Helianthus annuus) is a member of the Asteraceae family that's well suited to U.S. Department of Agriculture plant hardiness zones 2 to 11. Depending on the variety, sunflowers can grow anywhere from 1 to 15 feet tall. If you lack garden space, or if you simply want to brighten up your home, this annual upright grower can do the trick.
Choose a small variety for indoor growing. Grow your sunflowers in large, individual containers with drainage holes and well-drained potting mix. This accommodates the plant's fast growth and prevents sitting water.
Place the sunflowers in an area where they're exposed to at least six hours of full sunlight per day - an east or south-facing window is ideal. If needed, place the pots outside on a sunny patio or balcony, or expose them to fluorescent full spectrum lights. The sunflowers won't grow and flower well if they don't receive enough light.
Put a saucer or tray underneath each pot and soak the soil with a watering can until the liquid drains from the drainage holes. Avoid getting the foliage wet and always discard the drained water. Water the sunflowers when the top inch of soil is dry. Aim to keep the soil moist -- not soggy. For optimum growth, especially focus on regular watering about 20 days before and after flowering.
Fertilize the sunflowers with a water-soluble house plant fertilizer during the growing season. Avoid over-fertilizing, because this may stimulate foliage growth instead of flower growth.
Stake the sunflowers if they grow taller than 3 feet and become top-heavy. Use fabric-covered plant ties to loosely attach the stems to the stakes.