Pelargonium

The name Pelargonium was first proposed by Dillenius in 1732,[12] who described and illustrated seven species of geraniums from South Africa that are now classified as Pelargonium.[13][14] Dillenius, who referred to these seven species with apparent unique characteristics as Geranium Africanum (African Geranium)[15] suggested "Possent ergo ii, quibus novi generis cupido est, ea, quorum flores inaequales vel et irrregulares sunt, Pelargonia vocare" (Those who wish a new genus can therefore call those, whose flowers are unequal or irregular, ‘Pelargonia’).[7] The name was then formally introduced by Johannes Burman in 1738. However Carl Linnaeus who first formally described these plants in 1753 did not recognise Pelargonium and grouped together in the same genus (Geranium) the three similar genera Erodium, Geranium, and Pelargonium.[16] Linnaeus' reputation prevented further differentiation for forty years.[14] The eventual distinction between them was made by Charles L’Héritier based on the number of stamens or anthers, seven in the case of Pelargonium. In 1774, P. cordatum, P. crispum, P. quercifolium and P. radula were introduced, followed by P. capitatum in 1790.[17][13]

Pelargonium is distinguished from the other genera in the family Geraniaceae by the presence of a hypanthium, which consists of an adnate nectar spur with one nectary, as well as a generally zygomorphic floral symmetry.[8]

De Candolle first proposed dividing the genus into 12 sections in 1824, based on the diversity of growth forms.[18] Traditionally the large number of Pelargonium species have been treated as sixteen sections,[9][19] based on the classification of Knuth (1912) who described 15 sections,[20] as modified by van der Walt et al. (1977-1997) who added Chorisma, Reniformia and Subsucculentia.

These are as follows;

• section Campylia (Lindley ex Sweet) de Candolle
• section Chorisma (Lindley ex Sweet) de Candolle
• section Ciconium (Sweet) Harvey
• section Cortusina (DC.) Harvey
• section Glaucophyllum Harvey
• section Hoarea (Sweet) de Candolle
• section Isopetalum (Sweet) de Candolle
• section Jenkinsonia (Sweet) de Candolle
• section Ligularia (Sweet) Harvey
• section Myrrhidium de Candolle
• section Otidia (Lindley ex Sweet) de Candolle
• section Pelargonium (Sweet) Harvey
• section Peristera de Candolle
• section Polyactium de Candolle
• section Reniformia (Knuth) Dreyer
• section Subsucculentia J.J.A. van der Walt

All subdivision classifications had depended primarily on morphological differences till the era of phylogenetic analyses (Price and Palmer 1993).[11] However phylogenetic analysis shows only three distinct clades, labelled A, B and C.[21] In this analysis not all sections were monophyletic, although some were strongly supported including Chorisma, Myrrhidium and Jenkinsonia, while other sections were more paraphyletic. This in turn has led to a proposal, informal at this stage, of a reformulation of the infrageneric subdivision of Pelargonium.

In the proposed scheme of Weng et al. there would be two subgenera, based on clades A+B, and C respectively and seven sections based on subclades. Subsequent analysis with an expanded taxa set confirmed this infrageneric subdivision into two groups which also correspond to chromosome length (<1.5 μ, 1.5-3.0μ),[8] but also two subclades within each major clade, suggesting the presence of four subgenera, these correspond to clades A, B, C1 and C2 of the earlier analysis, A being by far the largest clade with 141 taxa. As before the internal structure of the clades supported monophyly of some sections (Myrrhidium, Chorisma, Reniformia, Pelargonium, Ligularia and Hoarea) but paraphyly in others (Jenkinsonia, Ciconium, Peristera). A distinct clade could be identified within the paraphyletic Polyactium, designated section Magnistipulacea. As a result, Polyactium has been split up to provide this new section, which in itself contains two subsections, Magnistipulacea and Schizopetala, following Knuth's original treatment of Polyactium as having four subsections.[8]

Subgenus Magnipetala section Chorisma: P. tetragonum

Subgenus Parvulipetala section Isopetalum: P. cotyledonis

Subgenus Paucisignata section Ciconium: P. acetosum

Subgenus Pelargonium section Campylia: P. tricolor

Subgenus Pelargonium section Otidia: P. crithmifolium

Thus Röschenbleck et al. (2014) provide a complete revision of the subgeneric classification of Pelargonium based on four subgenera corresponding to their major clades (A, B, C1, C2);

• subgenus Magnipetala Roeschenbl. & F. Albers Type: Pelargonium praemorsum (Andrews) F Dietrich
• subgenus Parvulipetala Roeschenbl. & F. Albers Type: Pelargonium hypoleucum Turczaninow
• subgenus Paucisignata Roeschenbl. & F. Albers Type: Pelargonium zonale (L.) L'Hér. in Aiton
• subgenus Pelargonium L'Hér. Type: Pelargonium cucullatum (L.) Aiton[8]

Sixteen sections were then assigned to the new subgenera as follows, although many species remained only assigned to subgenera at this stage

• subgenus Magnipetala 3 sections
  • section Chorisma (Lindley ex Sweet) de Candolle - 4 species
  • section Jenkinsonia (Sweet) de Candolle - 11 species
  • section Myrrhidium de Candolle - 8 species
• subgenus Parvulipetala 3 sections
  • section Isopetalum (Sweet) de Candolle - 1 species (Pelargonium cotyledonis (L.) L'Hér.)
  • section Peristera de Candolle - 30 species
  • section Reniformia (Knuth) Dreyer - 8 species
• subgenus Paucisignata 2 sections
  • section Ciconium (Sweet) Harvey - 16 species
  • section Subsucculentia J.J.A. van der Walt - 3 species
• subgenus Pelargonium 8 sections
  • section Campylia (Lindley ex Sweet) de Candolle - 9 species
  • section Cortusina (DC.) Harvey - 7 species
  • section Hoarea (Sweet) de Candolle - 72 species
  • section Ligularia (Sweet) Harvey - 10 species
  • section Magnistipulacea Roeschenbl. & F. Albers Type: Pelargonium schlecteri Knuth - 2 subsections
    • subsection Magnistipulacea Roeschenbl. & F. Albers Type: Pelargonium schlecteri Knuth - 2 species (P. schlecteri & P. luridum)
    • subsection Schizopetala (Knuth) Roeschenbl. & F. Albers Type: Pelargonium caffrum (Eckl. & Zeyh.) Steudel - 3 species (P. caffrum, P. bowkeri, P. schizopetalum)
  • section Otidia (Lindley ex Sweet) de Candolle - 14 species
  • section Pelargonium L'Hér. - 34 species
  • section Polyactium de Candolle - 2 subsections
    • subsection Caulescentia Knuth - 1 species (Pelargonium gibbosum)
    • subsection Polyactium de Candolle - 7 species

Subgenus Magnipetala: Corresponds to clade C1, with 24 species. Perennial to short lived, spreading subshrubs, rarely herbaceous annuals. Petals five, but may be four, colour mainly white. Mainly winter rainfall region of South Africa, spreading into summer rainfall region. One species in northern Namibia and Botswana. Two species in East Africa and Ethiopia. Chromosomes x=11 and 9.

Subgenus Parvulipetala: Corresponds to clade B, with 39-42 species. Perennials, partly annuals. Petals five and equal, colour white or pink to deep purplish red. Mainly South Africa, but also other southern hemisphere except South America. a few species in East Africa and Ethiopia. Chromosomes x=7-19.

Subgenus Paucisignata: Corresponds to clade C2, with 25-27 species. Erect sometimes trailing shrubs or subshrubs, rarely geophytes or semi-geophytes. Petals five and equal, colour pink to red sometimes white. Summer rainfall region of South Africa, spreading into winter rainfall region and northern Namibia, with a few species in tropical Africa, Ethiopia, Somalia, Madagascar, the Arabian Peninsula and Asia Minor. Chromosomes x=mainly 9 or 10, but from 4-18.

Subgenus Pelargonium: Corresponds to clade A, with 167 species. Frequently xerophytic deciduous perennials with many geophytes and succulent subshrubs, less frequently woody evergreen shrubs or annual herbs. Petals five, colour shades of pink to purple or yellow. Winter rainfall region of South Africa and adjacent Namibia, spreading to summer rainfall area, and two species in tropical Africa. Chromosomes x=11, may be 8-10.[8]

Pelargonium has around 280 species.[4][21] Röschenbleck et al lists 281 taxa.[8] There is considerable confusion as to which Pelargonium are true species, and which are cultivars or hybrids. The nomenclature has changed considerably since the first plants were introduced to Europe in the 17th century.[22]

The geranium bronze butterfly is a pest of Pelargonium species. The larvae of the geranium bronze bore into the stem of the host plant, causing the stem to typically turn black and die soon after. Geranium bronze are currently listed as an A2 quarantine pest by the European and Mediterranean Plant Protection Organization and can cause significant damage to Pelargonium species.[33]

The first species of Pelargonium known to be cultivated was P. triste, a native of South Africa. It was probably brought to the Botanical Garden in Leiden before 1600 on ships which had stopped at the Cape of Good Hope. In 1631, the English gardener John Tradescant the elder bought seeds from Rene Morin in Paris and introduced the plant to England. By 1724, P. inquinans, P. odoratissimum, P. peltatum, P. vitifolium, and P. zonale had been introduced to Europe.[17]

Zonal pelargonium

There was little attempt at any rational grouping of Pelargonium cultivars, the growing of which was revived in the mid-twentieth century, and the origins of many if not most were lost in obscurity. In 1916 the American botanist Liberty Hyde Bailey (1858–1954) introduced two new terms for zonal and regal pelargoniums. Those pelargoniums which were largely derived from P. zonale he referred to as P. × hortorum (i.e. from the garden), while those from P. cucullatum he named P. × domesticum (i.e. from the home).[39][40] In the late 1950s a list (the Spalding List) was produced in the United States, based on nursery listings and the 1897 list of Henri Dauthenay.[41] It described seven groups, listing each cultivar with the list of its originator, and in most cases a date. These were Species, Zonals, Variegated-Leaved, Domesticum (Regals), Ivy-Leaved, Scented-Leaved and Old. In the 1970s the British Pelargonium and Geranium Society produced a checklist and the Australian Geranium Society started to produce a register but it was not completed till its author, Jean Llewellyn's death in 1999. None of these were published. The most complete list in its time was the 2001 compilation by The Geraniaceae Group,[42] which included all cultivars up to 1959.[43]

Registration of cultivars is the responsibility of the Pelargonium & Geranium Society (PAGS: formed in 2009 from the British Pelargonium and Geranium Society and the British and European Geranium Society)[44] which administers the International Register of Pelargonium Cultivars.[45] PAGS is the International Cultivar Registration Authority (ICRA) of the International Society for Horticultural Science for pelargoniums.[46]

Contrasting leaves: Ivy-leaved Group (Left) Zonal Group (Right)

Cultivated pelargoniums are commonly divided into six groups[47] in addition to species pelargoniums and primary hybrids. The following list is ordered by position in the PAGS classification.[48] Abbreviations indicate Royal Horticultural Society usage.[49]

• A. Zonal (Z)
• B. Ivy-leaved (I)
• C. Regal (R)
• D. Angel (A)
• E. Unique (U)
• F. Scented-leaved (Sc)
• G. Species
• H. Primary hybrids

Of these, A, U and Sc groups are sometimes lumped together as Species Derived (Sppd). This term implies that they are closely related to a species from which they were derived, and do not fit into the R, I or Z groups.[50]

In addition to the primary groups, additional descriptors are used. The Royal Horticultural Society has created description codes. These include;[49]

• Cactus (Ca)
• Coloured foliage (C)
• Decorative (Dec)
• Double (d)
• Dwarf (Dw)
• Dwarf Ivy-leaved (Dwl)
• Frutetorum (Fr)
• Miniature (Min)
• Miniature Ivy-leaved (MinI)
• Stellar (St)
• Tulip (T)
• Variegated (v)

These may then be combined to form the code, e.g. Pelargonium 'Chelsea Gem' (Z/d/v), indicating Zonal Double with variegated foliage.[51] Crosses between groups are indicated with an ×, e.g. Pelargonium 'Hindoo' (R × U), indicating a Regal × Unique cross.[52]

Pelargonium × hortorum (Zonal)

These are known as zonal geraniums because many have zones or patterns in the center of the leaves,[36] this is the contribution of the Pelargonium zonale parent. Common names include storksbill, fish or horseshoe geraniums.[50] They are also referred to as Pelargonium × hortorum Bailey. Zonal pelargoniums are tetraploid, mostly derived from P. inquinans and P. zonale,[53] together with P. scandens and P. frutetorum.[36][47]

Zonal pelargoniums are mostly bush-type plants with succulent stems grown for the beauty of their flowers, traditionally red, salmon, violet, white or pink.[36] The scarlet colouring is attributed to the contribution of P. inquinans.[17] Flowers may be double or single. They are the pelargoniums most often confused with genus Geranium, particularly in summer bedding arrangements. This incorrect nomenclature is widely used in horticulture, particularly in North America.[17]

Zonals include a variety of plant types along with genetic hybrids such as hybrid ivy-leaved varieties that display little or no ivy leaf characteristics (the Deacons varieties), or the Stellar varieties. Hybrid zonals are crosses between zonals and either a species or species-derived pelargonium.[50] There are hundreds of zonal cultivars available for sale,[54] and like other cultivars are sold in series such as 'Rocky Mountain',[55] each of which is named after its predominant colour, e.g. 'Rocky Mountain Orange', 'White', 'Dark Red', etc.[56]

'Rocky Mountain Orange' (Zonal)

• (i) Basic plants – Mature plants with foliage normally exceeding 180 mm (7 in) in height above the rim of the pot. For exhibition these should be grown in a pot exceeding 120 mm (4+3⁄4 in) in diameter but not normally exceeding 165 mm (6+1⁄2 in).
• (ii) Dwarf plants – Smaller than basic. Mature plants with foliage more than 125 mm (5 in) above the rim of the pot, but not normally more than 180 mm (7 in). For exhibition should be grown in a pot exceeding 90 mm (3+1⁄2 in) but not exceeding 120 mm (4+3⁄4 in). They should not exceed 200 mm in height, grown in an 11 cm pot.[50]
• (iii) Miniature plants – Slowly growing pelargoniums. Mature plants with foliage normally less than 125 mm (5 in) above the rim of the pot. For exhibition should be grown in a pot not exceeding 90 mm (3+1⁄2 in). They should not exceed 125 mm in height, grown in a 9 cm pot.[50]
• (iv) Micro-miniature plants – Smaller and more slowly growing than miniature pelargoniums. Mature plants with foliage normally less than 100 mm (4 in) above the rim of the pot. They should not exceed 75 mm in height, grown in a 6 cm pot.[50] Usually no separate classes for these in exhibition and will therefore normally be shown as Miniature Zonals.
• (v) Deacon varieties –Genetic hybrid similar to a large Dwarf. For exhibition (when shown in a separate class), usually grown in a pot not exceeding 125 mm (5 in), otherwise as for Dwarf Zonals.
• (vi) Stellar varieties – A relatively modern genetic hybrid originating from the work done by the Australian hybridiser Ted Both in the late 1950s and 1960s from crosses between Australian species and Zonal types. Easily identifiable by their distinctive half-star-shaped leaves and slim-petalled blooms which create an impression of being star shaped (or five fingered). Single varieties tend to have larger elongated triangular petals whereas doubles tend to have thin feathered petals that are tightly packed together. For exhibition purposes there is a separate class for 'Stellar' varieties, but being Zonals could be shown in an open class for Basic, Dwarf or Miniature Zonals (unless otherwise stated). Also known as "The Five-fingered Geraniums", "Staphysagroides", "Both’s Staphs", "Both’s Hybrid Staphs", "Fingered Flowers" and "Bodey’s Formosum Hybrids".[50]

Fancy-leaf zonal pelargoniums – besides having green leaves with or without zoning, this group also have variable coloured foliage[50] that is sometimes used in classifying for exhibition purposes, e.g. ‘Bicolour’, ‘Tricolour’, ‘Bronze’ or ‘Gold’. Other foliage types are: ‘Black’ or ‘Butterfly’. There are an increasing number of these plants with showy blooms;

• (a) Bicolour – includes those with white or cream veined leaves or those with two distinct colours with clearly defined edges, other than the basic zone.
• (b) Tricolour – (May be Silver Tricolour (usually called a Silver Leaf) or a Gold Tricolour).
  • (i) Gold Tricolour – Leaves of many colours including red and gold, but usually with clearly defined edges of golden yellow and having a leaf zone, usually red or bronze, that overlays two or more of the other distinct leaf colours, so that the zone itself appears as two or more distinct colours.
  • (ii) Silver Tricolour or Silver Leaf – These tend to resemble a normal bi-colour leaf plant with two distinct colours usually of green and pale cream or white; the third colour is usually made up of bronze zoning. When this zoning overlays the green part of the leaf it is deemed to represent a silver colour.
• (c) Bronze Leaved – Leaves of Green or Golden/Green with a heavy bronze or chestnut coloured centre zone which is known as a medallion. For exhibition purposes, when exhibited in specific ‘Bronze’ Leaf class – Must have over 50% of leaf surface bronze coloured. The dwarf plant ‘Overchurch’ which has a heavy bronze medallion.
• (d) Gold Leaved – Leaves coloured golden/yellow or green/yellow but not showing a tendency to green. For exhibition purposes, when exhibited in specific ‘Gold’ Leaf class – Must have over 50% of leaf surface gold coloured.
• (e) Black Leaved – Leaves coloured black, purple-black or with distinct large dark zones or centre markings on green.
• (f) Butterfly Leaved – Leaves with a butterfly marking of distinct tone or hue in centre of leaf. This can be encompassed in many of the coloured leaf varieties.

Zonal pelargoniums have many flower types, as follows:[50]

• (a) Single flowered (S) – each flower pip normally having no more than five petals. This is the standard flower set for all Pelargoniums.
• (b) Semi-double flowered (SD) – each flower pip normally having between six and nine petals.
• (c) Double flowered (D)– each flower pip composed of more than nine petals (i.e. double the standard flower set) but not ‘hearted’ like the bud of a rose, e.g. the dwarf ‘Dovepoint’ which has full double blooms.
• (d) Rosebud (or noisette) flowered – each bloom fully double and ‘hearted’. The middle petals are so numerous that they remain unopened like the bud of a rose.[50]
• (e) Tulip flowered – having semi-double blooms that never fully open. The large cup shaped petals open just sufficiently to resemble a miniature tulip.
• (f) Bird's-egg group – having blooms with petals that have spots in a darker shade than the base colour, like many birds eggs.[50]
• (g) Speckled flowered group – having petals that are marked with splashes and flecks of another colour, e.g. ‘Vectis Embers’.
• (h) Quilled (or cactus-flowered group, or poinsettia in USA) – having petals twisted and furled like a quill.[50]

“Zonquil” pelargoniums result from a cross between Zonal pelargonium cultivars and P. quinquelobatum.[50]

Pelargonium peltatum (Ivy-leaved)

Also known as "ivy geraniums".[50]Usually of lax growth (trailing), mainly due to the long thin stems, with thick, waxy ivy-shaped stiff fleshy evergreen leaves developed by the species P. peltatum to retain moisture during periods of drought. Much used for hanging pots, tubs and basket cultivation. In the UK the bulbous double-headed types are preferred whilst on the European continent the balcon single types for large-scale hanging floral displays are favoured. Ivy-leaved pelargoniums embrace all such growth size types including small-leaved varieties and genetic hybrid crosses, which display little or no zonal characteristics. May have bicolour leaves and may have flowers that are single, double or rosette. Ivy pelargoniums are often sold as series such as 'Great Balls of Fire', in a variety of colours such as 'Great Balls of Fire Burgundy'.

Additional descriptive terms include;[50]

• Hybrid Ivy — the result of ivy × zonal crosses, but still more closely resemble ivy-leaved pelargoniums.
• Fancy leaf — leaves with marked color variation, together with or other than green.
• Miniature — miniature leaves and flowers, stems with short nodes, and compact growth. e.g. 'Sugar Baby'[57] listed as Dwarf Ivy (DwI) by RHS.[49]

'Karl Offenstein' (Regal)

These are large bush-type floriferous evergreen pelargoniums. In addition to "Regals" they are also known as “Show Pelargoniums”. In the United States they are often known as the "Martha Washington" or ‘"Lady Washington" pelargoniums. They are grown primarily for the beauty and richness of their flower heads, which are large. Most of those cultivars grown currently are the result of hybridization over the last 50 years. They are very short-jointed and compact, which results in their requiring very little work in order to create a floriforous and well-rounded plant.[50][48] Flowers are single, rarely double, in mauve, pink, purple or white. They have rounded, sometimes lobed or partially toothed (serrated) leaves, unlike the Zonal groups, without any type of zoning.

Additional descriptive terms include;[50]

• Fancy leaf – Leaves with marked variations in colour
• Decorative pelargoniums (Decoratives) – Descendants of older, less compact, smaller-flowered varieties that are more suited to outdoor conditions. These have smaller flowers than Regal, but are otherwise similar. e.g. ‘Royal Ascot’
• Miniature – Flowers and leaves similar to Regal, but miniature in form, with compact growth. Other terms include “Pansy Geraniums” or “Pansy Pelargoniums”. e.g. ‘Lara Susan’
• Oriental pelargoniums – The result of crosses between Regals and members of the Angel group (see below). Some have bicolour foliage.

'Angeleyes Randy' (Angel)

Angel pelargoniums are similar to Regal pelargoniums but more closely resemble P. crispum in leaf shape and growth habit. The majority of Angel cultivars originate from a cross between P. crispum and a Regal variety in the early part of the 20th century. Angels have grown in popularity in the last 30 years or so due mainly to an explosion of new varieties being released by specialist nurseries resulting from the work done by dedicated amateur hybridisers. These hybrisers have managed to obtain many new flower colour breaks and tighter growth habits resulting in plants suitable for all sorts of situations. Angels basically have the appearance of a small Regal with small serrated leaves and much smaller flowers and are more compact and bushy. The group extends to include similar small-leaved and -flowered types but usually with P. crispum in their parentage. They are mostly upright bush-type plants but there are some lax varieties that can be used for basket or hanging pot cultivation. Often called "pansy-faced" in the US. Some varieties have bicolour foliage. Other terms include ‘Langley-Smith Hybrids’.[50]

'White Unique' (Unique)

Unique in sense of not fitting into any of the above categories. The parentage of Unique pelargoniums is confused and obscure. One theory being a derivation from P. fulgidum, but a derivation from an older cultivar 'Old Unique’, also known as or ‘Rollinson’s Crimson’, in the mid-19th century is also claimed.[50] Unique pelargoniums resemble upright Scented Leaf pelargoniums in being shrubby and woody evergreens. They have distinctly scented leaves, and small flowers with blotched and feathered petals. They may have bicolour foliage. Some types, popularly known in the hobby as hybrid Uniques, have been crossed with Regal pelargoniums and, as a result of this cross, are much more floriferous.

Cultivar

• Fiery-flowered Stork's-bill, Scarlet Unique Scented Geranium (P. × ignescens)[58] - a P. fulgidum hybrid[59]

Pelargonium graveolens (Scented leaf)

Shrubby evergreen perennials grown chiefly for their fragrance, may be species or cultivars but all must have a clear and distinct scented foliage. Scent is emitted when the leaves are touched or bruised with some scents aromatic, others pungent and in a few cases, quite unpleasant. Several of the scented leaved pelargoniums are grown for the oil geraniol, which is extracted from the leaves and is an essential oil much used commercially in perfumery. The scent of some species growing in their natural habitat, acts as a deterrent to grazing animals who appear to dislike the emitted scent. Conversely, it also attracts other insect life to visit the bloom and pollinate the plant. The scented leaves can be used for potpourri and they also have a use as flavourings in cooking. Occasionally scented types can be found in some of the other groups mentioned; for example, the Angels, having P. crispum in their genetic makeup, can often have a strong citrus scent. Leaves are lobed, toothed, incised or variegated. Growth habit is very variable, but the flowers are less prominent than other groups, and most closely resemble the species they originated from.[50]

These include:

Pelargonium quercifolium 'Fair Ellen' (Scented leaf)

Pelargonium ionidiflorum (Scented leaf)

• Almond - Pelargonium quercifolium
• Apple - Pelargonium odoratissimum
• Apple - Pelargonium cordifolium
• Apple/Mint - Pelargonium album
• Apricot/Lemon - Pelargonium scabrum
• Balsam - Pelargonium panduriforme
• Camphor - Pelargonium betulinum
• Celery - Pelargonium ionidiflorum
• Cinnamon - Pelargonium 'Ardwyck Cinnamon'
• Coconut - Pelargonium grossalarioides (Pelargonium parriflorum)
• Eau de Cologne - Pelargonium 'Brilliantine'
• Eucalyptus - Pelargonium 'Secret Love'
• Grapefruit - Pelargonium 'Poquita'
• Ginger - Pelargonium 'Torrento' or 'Cola Bottles' which is a variety of Pelargonium x nervosum
• Hazelnut - Pelargonium 'Odorata Hazelnut
• Lavender - Pelargonium 'Lavender Lindy'
• Lemon - Pelargonium crispum
• Lemon - Pelargonium citronellum (Synonym - Pelargonium 'Mabel Grey')
• Lemon Balm - Pelargonium x melissinum
• Lime - Pelargonium x nervosum
• Myrrh - Pelargonium myrrhifolium
• Nutmeg - Pelargonium x fragrans
• Old Spice - Variety of Pelargonium x fragrans
• Orange - Pelargonium x citriodorum (Synonym - Pelargonium 'Prince of Orange')
• Peach - Pelargonium 'Peaches and Cream'
• Peppermint - Pelargonium tomentosum
• Pine - Pelargonium denticulatum
• Pineapple - Pelargonium 'Brilliant'
• Raspberry - Pelargonium 'Red Raspberry'
• Rose - Pelargonium graveolens (Synonym - Pelargonium roseum)
• Rose - Pelargonium capitatum
• Rose - Pelargonium radens
• Southernwood - Pelargonium abrotanifolium
• Spicy - Pelargonium exstipulatum
• Strawberry - Pelargonium x scarboroviae

Cultivars

• 'Attar of Roses' - a cultivar of P. capitatum
• 'Crowfoot Rose' - a cultivar of P. radens
• 'Dr. Livingston' - a cultivar of P. radens
• 'Grey Lady Plymouth' - a cultivar of P. graveolens
• 'Prince Rupert' - a cultivar of P. crispum

The species are the forefathers of all the cultivar groups listed above. In general, the definition of a species is that it breeds true, and is to be found doing this in the "wild". Species pelargoniums have a large diversity of characteristics in habit, shape, size and colour, which probably accounts for them having retained their popularity for more than 300 years.

A primary hybrid is recognised as being the resultant plant from a first-time cross between two different known species. Examples are P. × ardens – from P. lobatum × P. fulgidum (1810). P. × glauciifolium – from P. gibbosum × P. lobatum (1822). Usually, but not always, primary hybrids are sterile.

'Attar of Roses'

'Lady Plymouth'

'Mabel Gray'

The following is a selection of pelargoniums which have gained the Royal Horticultural Society's Award of Garden Merit:

• 'Attar of Roses' (rose scented leaves, pink flowers)[60]
• 'Citriodorum' (lemon scented leaves, rose pink flowers)[61]
• 'Dolly Varden' (variegated leaves, scarlet flowers)[62]
• 'Frank Headley' (cream vareigated leaves, salmon pink flowers)[63]
• 'Fringed Aztec' (white & purple fringed flowers)[64]
• 'Gemstone' (scented leaves, pink flowers)[65]
• 'Grace Thomas' (lemon scented leaves, pale pink flowers)[66]
• 'Joy' (pink & white frilled flowers)[67]
• 'Lady Plymouth' (P. graveolens variegata - small mauve flowers)[68]
• 'Lara Candy Dancer' (scented leaves, pale mauve flowers)[69]
• 'Lara Starshine' (aromatic leaves, lilac flowers)[70]
• 'L'Élégante' (ivy-leaved, trailing, white and purple flowers)[71]
• 'Mabel Grey' (lemon-scented leaves, mauve flowers)[72]
• 'Mrs Quilter' (bronze leaves, salmon pink flowers)[73]
• 'Radula' (lemon & rose scented leaves, pink & purple flowers)[74]
• 'Royal Oak' (balsam scented leaves, mauve flowers)[75]
• 'Spanish Angel' (lilac & magenta flowers)[76]
• 'Sweet Mimosa' (balsam-scented leaves, pale pink flowers)[77]
• 'Tip Top Duet' (pink & wine-red flowers)[78]
• 'Voodoo' (crimson & black flowers)[79]
• P. tomentosum (peppermint-scented leaves, small white flowers)[80]

Pelargoniums rank as one of the highest number of potted flowering plants sold and also in terms of wholesale value.[36]

Other than being grown for their beauty, species such as P. graveolens are important in the perfume industry and are cultivated and distilled for their scents. Although scented pelargoniums exist which have smells of citrus, mint, pine, spices or various fruits, the varieties with rose scents are most commercially important. Pelargonium distillates and absolutes, commonly known as "scented geranium oil" are sometimes used to supplement or adulterate expensive rose oils. The oils of the scented pelargoniums contain citronellol, geraniol, eugenol, alpha pinene and many other compounds. The edible leaves and flowers are also used as a flavouring in desserts, cakes, jellies and teas. Scented-leafed pelargoniums can be used to flavor jellies, cakes, butters, ice cream, iced tea and other dishes, The rose-, lemon- and peppermint-scents are most commonly used. Also used are those with hints of peach, cinnamon and orange. Commonly used lemon-scented culinary species include P. crispum and P. citronellum. Rose-scenteds include P. graveolens and members of the P. graveolens cultivar group. Other species and cultivars with culinary use include the lime-scented P. ‘Lime’, the lemon balm-scented P. ‘Lemon Balm’, the strawberry-lemon-scented P. ‘Lady Scarborough’ and the peppermint-scented P. tomentosum.[81] Scented leaf pelargoniums have also been historically used as toilet paper by fishermen in remote places, such as the Minquiers.[82]

In herbal medicine, Pelargonium has been used for intestinal problems, wounds and respiratory ailments, but Pelargonium species have also been used for fevers, kidney complaints and other conditions. Geranium (Pelargonium) oil is considered a relaxant in aromatherapy, and in recent years, respiratory/cold remedies made from P. sidoides and P. reniforme have been sold in Europe and the United States.[81] P. sidoides along with Echinacea is used for bronchitis.[83] P. odoratissimum is used for its astringent, tonic and antiseptic effects. It is used internally for debility, gastroenteritis, and hemorrhage and externally for skin complaints, injuries, and neuralgia and throat infections. The essential oil is used in aromatherapy.[84]

According to the ASPCA, these plants are toxic to cats, dogs, and horses.[85]

Pelargonin (pelargonidin 3,5-O-diglucoside) is a petal pigment of the scarlet pelargonium.[86]