Martha Washington geraniums, also known as regal geraniums, are not "true" geraniums but instead are pelargoniums. Martha Washington geraniums are not suitable for growing outdoors in most warm climates, because they require cool nighttime and relatively cooler daytime temperatures throughout the growing season in order to bloom. Often used as potted-plant gifts, Martha Washingtons are technically annual flowers, but you can get them to re-bloom under the right conditions. These pelargoniums can grow up to 22 inches tall and 24 inches wide at maturity, blooming throughout the spring and summer.
Pot your Martha Washington geraniums in containers that are about 18 to 24 inches in diameter and filled with rich, all-purpose potting soil. Ensure that the containers have drainage holes in the bottom.
Place the Regal geraniums in full to partial sunlight, such as in a sunny, south-facing window. Keep air temperatures between 60 and 65 degrees F during the day and around 50 to 55 degrees at night.
Water your Martha Washington geraniums once or twice each week when the top 1 or 2 inches of potting soil feels dry to the touch.
Feed your geraniums a balanced liquid flower fertilizer once each month during the spring and summer. Apply the fertilizer according to the directions on the label when you're watering the plant.
Pinch off the faded blooms to encourage new flowers to emerge. Snip the spent flowers off with sharp scissors or remove them with your fingers.