Pelargoniums & geraniums
You say geranium… but really it could be pelargonium. Still, there are many reasons to love them both.
A plant-lover’s guide
formal plant identification can be a confusing business. Botanists often change their minds about which genus a plant belongs to, leading to the use of a variety of botanical names, depending on which nursery or garden centre you frequent. And then there is the plethora of common names to contend with. This is not a recent phenomenon. It has happened for centuries in the world of horticulture, ever since the first plant hunters starting taking plants from around the globe back to Europe.
Such is the case with pelargoniums and geraniums, both part of the Geraniaceae family and both originally classified as belonging to the same Geranium genus due to the fact that their seed capsules are similar. Even though the two were separated into two genera some 250 years ago by French botanist Charles L’Heritier, many growers and gardeners, particularly in the US, continue to call pelargoniums geraniums.
What’s the difference?
The flowers of geranium and pelargonium are not the same. Geranium flowers have five similar petals; pelargonium blooms have two upper petals which are different from the three lower petals.
True geraniums, often called cranesbill geranium or hardy geranium, are mostly found growing naturally in the east Mediterranean and other temperate regions including New Zealand. There are around 422 species in the Geranium genus, many of them flowering annual, biennial and perennial plants. We have eight native geranium species that have been formally identified, possibly up to 20 altogether. The most well-known is Geranium traversii from the Chatham Islands and the most recently named is Geranium aff. retrorsum ‘Oakley Creek’, discovered in Auckland by botanist Rhys Gardner during a study of the Oakley Creek area prior to the construction of the Waterview Tunnel.
Within the Pelargonium genus are perennials, subshrubs, shrubs and succulents. All up, there are around 280 species. They’re mainly found growing naturally in a range of habitats from mountains to deserts in the southern regions of Africa, particularly South Africa and Namibia. The Pelargonium genus also extends to northern and eastern parts of the African subcontinent, the Middle East, Turkey, Australia and New Zealand. Our little-known native species, also native to eastern Australia, is k¯opata ( Pelargonium inodorum) which has tiny pink flowers and bright green foliage. Most of the pelargonium plants cultivated in Europe and the US
originated in South Africa. These are not generally frost hardy and are often planted as annuals in colder climates.
The first pelargonium in Europe was
Pelargonium triste. It arrived at Leiden Botanical Gardens in the Netherlands around 1600, with cuttings taken to France and England soon after.
Enthusiasm for the species had grown rapidly by the mid-18th century as Dutch and British plant collectors took home seeds and plants from southern Africa to grow in nurseries in their respective countries.
However, as the political situation changed in Africa and plant collecting became more difficult, attention focused on breeding hybrids in Europe. In the Victorian era, pelargoniums were eagerly sought-after by gardeners and numerous cultivars were produced in England, Europe, Australia and the US, particularly California which had the ideal climate for cultivation (several species have naturalised on the coast there). Many of the early hybrid cultivars have now been lost although pelargonium and geranium societies around the world are trying to recreate them.
Pelargoniums had become victims of their own success by the end of the 19th century, with well-known figures William Morris and Oscar Wilde deriding what was then known as the scarlet geranium, used extensively as a bedding plant in borders, window boxes and pots at that time. Despite being seen as suburban and bourgeois though, the flowers refused to go away, says Kasia Boddy, author of Geranium (2013). Now they’re one of the world’s most popular plants once again, particularly in the US and Europe where they are prized as bedding and container plants.
Opinions differ on the number of groups within the Pelargonium genus. The Royal Horticultural Society lists seven, but the following five are the most commonly grown.
This is the largest and most common group, often described as bedding geraniums and seen in window boxes and pots everywhere in Europe. The name comes from the parent plant
Pelargonium zonale but they are usually referred to as Pelargonium x
hortorum, a hybrid of Pelargonium zonale and Pelargonium inquinans. Zonals are identified by the darkcoloured zones or patterns in the centre of the leaves. Most are semishrubby plants that traditionally produce red, salmon, violet, white or pink blooms in tight, rounded clusters, usually double or single. However there are several other flower types, including cactus, rosebud and tulip.
As well as container plants, smaller, compact zonal forms are often used as bedding plants. Look out for new colours in this group such as a yellow cultivar called ‘Allwoods Lemon Drizzle’ (allwoods.net).
Fancy-leaved pelargoniums have strongly defined leaf patterns, sometimes dark blotches or a type of white, grey or yellow leaf variegation, occasionally both. They’re grown as much for their leaves as their flowers.
Originating from Pelargonium
peltatum, these have a trailing growth habit that makes them excellent groundcovers and climbers to cover fences and other structures. They’re also often grown in hanging baskets, pots and window boxes.
Their ivy-shaped leaves are waxy, almost succulent, some with variegations.
Flowers of ivy-leaved pelargoniums can be single, double or rosette. New cultivars with stunning flower colours are now coming onto the
market, for example ‘PAC Tomcat’ which has dark burgundy flowers.
This is the second largest group, so named because they were raised at Sandringham Palace in the mid19th century. Regals, also known as Martha Washington pelargoniums in the US, are different to Zonal types in that plants are larger and more shrub-like. Their rounded, sometimes lobed or partially serrated leaves usually have no zoning colouration.
Regal flowerheads on tall stems are large and flamboyant, with a much more extensive colour range than other groups, some even bi-coloured or tri-coloured. Petals can be ruffled or fringed.
Regals are some of the earliest pelargoniums to flower in the spring but don’t bloom well in very hot, humid conditions. Modern cultivars have bigger flowers and plants won’t become as straggly as they age like older Regal pelargoniums do.
Many of these older Regals are disappearing from specialist nurseries. Most of the cultivars currently grown are the result of hybridisation during the last 50 years.
Often classed as a separate group are Angel pelargoniums (mostly derived from Pelargonium crispum) but they are very similar to Regals, just more compact and bushy. Flowers have a pansy-like appearance.
As their name suggests, this group of shrubby evergreen perennials are mainly grown for their fragrant foliage. The scent is emitted when the leaves are touched or bruised.
Flowers, although small, have a delicate beauty ranging from deep crimson to pale pink.
Heights are variable: some grow to over a metre; others only reach 30cm. Tip pruning can easily help control height.
Scented-leaved pelargoniums are very drought- and heat-tolerant. Over 400 years of plant breeding has produced 140 varieties with an impressive range of perfumes. These include rose, lime, lemon, nutmeg, peach, lemon, cinnamon, eucalyptus, grapefruit, almond ginger, nutmeg, oak, peppermint, strawberry, balsam, apricot, coconut and apple. Not surprisingly, many are grown commercially for their oil, which is used by the perfume industry.
Leaves can also be used medicinally as well as for potpourri, cooking, jams, even popped into a cold drink. Many are great plants for attracting pollinators to the garden.
In recent years, plant breeders in the US have created a new class of pelargonium by crossing Ivy-leafed geraniums with Zonal types. Said to provide new forms and colours as well as better performance, these interspecific pelargoniums, such as the Caliente and Calliope series, combine the heat tolerance of Zonals with the superior flowering ability of Ivy-leaved types (up to a third more blooms than Zonals).
Zealandia Horticulture supplies ‘Big Red’, one of the US-developed Calliope series to New Zealand retailers. “We have found this to be a superb growing plant which produces masses of beautiful, deep red flowers with the most intense colouring you will find in the market,” says its national sales coordinator Aaron Blackmore. “The plant itself has good vigour and will form a decent-sized bush that, at maturity, will produce more quality flowers than any conventional varieties that we have grown. “
Another red-flowering interspecific called ‘Cassiopeia’ will be released this year by Invercargill-based Hayes Wholesale. Founded by Barry Hayes 35 years ago, the company is the largest supplier of pelargoniums in the country as well as the New Zealand representative for ‘PAC’ varieties from Germany.
Geranium phaeum ‘Rose Madder’.
Pelargonium x hortorum ‘Mrs Strang’.
Pelargonium ‘Angeleyes Viola’.