Geranium, belongs to the Pelargonium family and unlike its distant cousin (a true geranium and hardy version) is a tender plant grown as an annual in cooler climates and a perennial in zone 10.
Geranium (P. x hortorum) or commonly known as zonal or garden geranium is a favorite for container plantings and flower beds because of its long blooming season and brilliant colors. It bears rounded clusters of individual flowers which are either single or double on a stem which rises above the rounded scalloped leaves. The fuzzy leaves may have zonal markings and emit a “fragrance” when touched.
Geranium requires little care as long as it gets full sun and well-drained, moist soil. In northern climates, they will tolerate light shade but if grown in shade will produce a leggy plant and little flowers. In southern climates, it is best to grow them in partial-sun with afternoon shade. Prolonged hot temperatures will trigger them to stop blooming.
For optimal bloom, feed the plant lightly with a well balanced fertilizer ( 10-10-10) once a month during the active growing season. Container plants may need to be fed more often (2x month) because the nutrients can leach out from the bottom of the pot when watering. They bloom best when slightly pot bound.
Geraniums need at least 1 inch of water per week. When watering, avoid getting the leaves and flowers wet, which can encourage fungal (Botrytis -gray mold) and bacterial disease. Container plants may need to be watered more often but should be allowed to dry slightly between watering. Take care not to overwater as it can cause root rot.
Plant your seedlings outdoors, when night temperatures are above 40F or after the last frost date. Setting the plants out too early can cause the leaves to turn red from cool night temperatures.
Remove spent flower stalks and yellowing leaves. Pinching back or trimming some of the stems will encourage more branching and eventually more flowers.
Another Pelargonium worth mentioning is P.x peltatum know as ivy geranium. It has smooth leaves and grows in a trailing manner making it ideal for hanging baskets.