Geraniums add lush foliage and brightly colored blossoms to any backyard or indoor garden. Their versatility helps make them one of the most popular flower plants for gardeners, according to North Carolina State University. Outdoors, they're generally hardy up to USDA hardiness Zone 4, but indoor plants can be grown anywhere. Though most garden stores and nurseries sell started geranium plants, starting your own geraniums at home from seed can save you money.
Place an inch of gravel on the bottom of a gallon-size pot or larger if you're growing the geraniums as a houseplant. If you're planning on transplanting the geraniums outdoors, use a seed tray or a quart-sized pot.
Fill the pot or seed tray with commercially prepared potting soil. If no potting soil is on hand, formulate your own. Iowa State University recommends mixing equal parts of vermiculite--sand is an acceptable substitute if vermiculite isn't available--with peat moss.
Water the soil thoroughly to moisten it. Wait 2 to 3 hours to allow any excess water to drain to the bottom of the pot.
Plant the geranium seeds. Bury each seed 1/8 inch under the soil surface at a rate of one seed per pot or seed tray compartment.
Moisten the soil surface again, then cover the pot or seed tray with plastic wrap. This traps the moisture inside the pot and helps keep the soil consistently moist.
Place the pot or seed tray near a sunny window but out of direct sunlight. The ideal temperature for starting geraniums is approximately 75 degrees Fahrenheit. The plants will start growing within one week, according to Iowa State University.
Transplant the seedlings outdoors if you don't plan on growing them as houseplants. Seedlings are ready for transplanting once they're 2 to 3 inches tall. Geranium plants thrive in full sun and in well-drained soil, according to the University of Rhode Island.