Just a note here: What most gardeners know as a “geranium” is probably a plant of the genus pelargonium and not the genus geranium (more commonly known as cranesbills). We are using the term ‘geranium’ here in deference to the common usage.
There are four main types of garden geraniums: zonal geraniums, Martha Washington geraniums, the scented-leaf geraniums, and ivy geraniums.
Zonal geraniums (pelargonium hortorum):
The most popular garden geraniums, getting their name from the “zoned” leaf markings. They have clusters of individual flowers held on long stems above the foliage. There are many cultivars, with a wide range of brilliant flower color and attractive leaves. Most will grow about 3 ft. tall.
Ivy geraniums (pelargonium peltatum):
Named for the ivy-shaped foliage and trailing growth habit; flower colors are more pastel than zonals. These are ideal for hanging baskets; they are also great for window boxes or as ground covers in a protected location. They like moderate temperatures. If they are in pots and the temperature is between 65 and 80 degrees F, put them in full sun. If it is hotter than that, move them to an area with partial sun.
Scented-leaf geraniums (pelargonium – various species and hybrids):
Grown for their beautifully scented foliage. They vary in shape, size, flower color and growth habit. Foliage fragrances include rose, chocolate, mint, apple, lemon, lime, ginger and nutmeg. We recommend placing them in areas where the fragance can be easily enjoyed.
Martha Washington geraniums (pelargonium domesticum):
The group known as the “orchid of geraniums.” Flowers are orchid-like blooms; colors may be white, pink, red, purple, or mixed colors. These geraniums require cool (50 to 60°F) night temperatures in order to bloom. They may stop flowering in the heat of the summer but will resume once the weather cools in the fall. We don’t recommend these for summer gardens, but some like them for spring and autumn.
For planting geraniums in flower beds, work in a complete fertilizer before planting. In mid-summer fertilize again with a water-soluble fertilizer. Space plants 10 to 12 inches apart. Water well after planting, but don’t overwater.
For planting in containers, use a good potting mix, which not only helps to retain moisture but also helps to prevent over-watering. Geraniums are commonly over-watered; they should be allowed to dry out completely between waterings and then watered thoroughly. Geraniums in pots should be fertilized regularly with a water-soluble fertilizer during their growth periods. Make sure to plant them in containers that drain well, as they are not fond of wet feet.
Geraniums of all sorts are a great addition to your home and garden. Try a few this year for your window boxes, hanging baskets, and flowerbeds.