Zinnias are annual flowers that come in many colors and styles, including single- and double-petaled flower heads. Depending upon the type of zinnias, they can grow from 8 inches to 4 feet tall, so before selecting zinnia seed, consider where they will be planted. Dwarf zinnias do great in pots, while the taller zinnias add a stunning background to any flower bed. No matter which type of zinnia you choose, to get a head start on the blooming season, start the seeds indoors.
Start zinnia seeds four to six weeks before the last expected frost.
Plant in peat pots that are 2 to 3 inches tall. Starting seeds in peat pots will do away with the need to re-pot as they grow.
Fill the pots with a seed-starter potting soil mix, leaving 1 inch of room at the top. Place the peat pots in a large seed tray and water until the soil is moist but not drenched.
Place three seeds on the soil and cover with 1/2 inch of soil mix. Moisten the top soil with a mist of water from a spray bottle.
Cover the pots with a large sheet of plastic wrap. Place the tray in a warm location with bright light. Germination should begin within six to 10 days.
Remove the plastic wrap. Place the seedlings in a bright, sunny window.
Continue to keep the soil moist, but water the plants from the bottom by keeping water in the seed tray. Check the soil inside the pot for moisture with your fingers.
Thin the number of seedlings in the pot by snipping the weaker ones off at the base.
Plant in the garden bed when the danger of frost has passed. Plant the peat pots directly into the ground, if desired, as they are biodegradable, or gently peel the pot away from the roots before planting.