Pelargoniums

South African relatives of geraniums!

Botanical Name: Pelargonium spp. Common Name: Geranium Family: Geraniaceae 

Description: Members of the genus Pelargonium are commonly called Geraniums. True Geraniums are a different genus and are commonly known as Cranesbills; however, both Pelargonium and Geraniums are in the family Geraniaceae. While Pelargoniums are perennial succulent shrubs, they are frequently grown as annuals in temperate climates. Originally from South Africa, they are drought tolerant, heat resistant and will survive minor frosts. The thousands of varieties can be divided into four main groups.

Cultivars: P. x hortorum , "Zonal pelargoniums," are what typically come to mind when someone says, "geranium". Zonals have lovely leaf coloring, typically green with a brown to black horseshoe-shaped zone. Golden-leaved are golden-chartreuse, many with a light chestnut zone in cool weather. Silver bicolors have white, ivory or golden ivory margins. They will bloom year-round if cared for properly. The golden-leaved do best in bright shade.

P. domesticum, "Regal pelargoniums" are also known as Martha Washington geraniums or French geraniums. They have large azalea-like flowers with dramatic colors and patterns including purple. Regals tend to be spring blooming but many modern hybrids will produce scattered blooms into early fall. For best bloom, prune back in the fall. Regals are a bit more cold tender than zonals and ivy-leaved.

P. domesticum, "Scented-leaf pelargoniums" are heirloom plants still grown today for their fragrance, essential oil, culinary use and foliage. The scent is created by oils in the leaves which are released when the leaves are brushed. Consider placement near pathways for maximum enjoyment. The fragrance of a scented geranium may remind you of rose, lemon, cloves, nutmeg, pine, peppermint, apple, apricot, pineapple, chocolate or coconut. To make up for the lack of floral display, many scented geraniums have decorative unique leaves.

P. peltatum, "Ivy-leaf pelargoniums" look great trailing down from patio pots, hanging baskets or window boxes. The cultivars 'Claremont' & 'Jeanne d'Arc' are particularly adept at clambering through shrubs & trees.

Cultivation: Pelargoniums like well drained soil. Water when the soil approaches dryness. If in doubt, don't water. Too much watering leads to lower leaves yellowing and dropping off. They need a minimum of four hours of sun each day. Most will be happy with full sun, especially in mild climates. In hot areas bright shade is better. The exceptions are golden-leaved zonals, peppermint and 'Chocolate Mint' scented-leaf. These prefer bright shade, and will tend to be stunted or burned when given too much full sun. Give them a Balanced fertilizer with all three numbers close to the same, up to 15-15-15. In containers it is important to provide a balanced complete fertilizer with secondary nutrients like sulfur, calcium & magnesium, plus the micro nutrients like iron, zinc, copper & others. Prune for airflow. In cold wet weather dead leaves are a perfect place for grey mold to grow, moving onto the living tissue & causing problems.

Common Problems: Indoors plants may suffer from aphids, mites, mealy bugs, and whitefly. Control with a houseplant insect spray used according to directions. Bacteria blight. Leaf spotting initially appears as tiny circular or angular lesions on the underside. The spots increase in size and become sunken. They may be surrounded by a yellow halo. Lesions eventually turn dark brown and become hard and dry and affected leaves wilt and die. The second common type of leaf symptom is characterized by wilted margins and V-shaped yellow lesions between the veins.

Control: Inspect plants carefully when purchasing. Buy disease free plants. Remove and destroy infected plants. Do not reuse soil and pots for other pelargoniums without sterilizing them first. Control pests which may spread the disease. The cutting knife or pruning tool is the most common means of spreading disease. In addition, bacterial cells are splashed to neighboring plants with irrigation water. Do not hang ivy geraniums above other geraniums. Avoid overhead irrigation. When propagating break rather than cut stems from parent plants and root in individual pots rather than flats. Links: http://en.wikipedia.org/wiki/Pelargonium http://flowergardens.suite101.com/article.cfm/scented_geranium_pelargonium http://www.newleafnurseries.com/ http://www.swanlandnurseries.co.uk/culturalnotes.asp http://ucce.ucdavis.edu/datastore/detailreport.cfm?usernumber=79&surveynumber=275

Submitted by Master Gardener Sakina Bush, 2007.