WhileGeranium species are mostlytemperate herbaceous plants, dying down in winter,Pelargonium species are evergreen perennialsindigenous to warm temperate and tropical regions of the world, with many species in southern Africa. They are drought and heat tolerant but can tolerate only minor frosts. Some species are extremely popular garden plants, grown as houseplants andbedding plants intemperate regions. They have a long flowering period, with flowers mostly in red, orange, or white, but intensive breeding has produced a huge array ofcultivars with great variety in size, flower colour, leaf form and aromatic foliage.
Pelargonium occurs in a large number ofgrowth forms, includingherbaceousannuals,shrubs, subshrubs, stemsucculents andgeophytes.[6] The erect stems bear five-petaledflowers inumbel-like clusters, which are occasionally branched. Because not all flowers appear simultaneously, but open from the centre outwards, this is a form of inflorescence is referred to as pseudoumbels.
The flower has a single symmetry plane (zygomorphic), which distinguishes it from theGeranium flower, which has radial symmetry (actinomorphic). Thus the lower three (anterior) petals are differentiated from the upper two (posterior) petals. The posteriorsepal is fused with thepedicel to form ahypanthium (nectary tube). The nectary tube varies from only a few millimeters, up to several centimeters, and is an important floral characteristic in morphological classification.Stamens vary from 2 to 7, and their number, position relative tostaminodes, and curvature are used to identify individual species. There are fivestigmata in thestyle.[7] For the considerable diversity in flower morphology, see figure 1 of Röschenblecket al. (2014).[6]
Leaves are usually alternate, andpalmately lobed orpinnate, often on long stalks, and sometimes with light or dark patterns. The leaves ofPelargonium peltatum (Ivy-leaved Geranium), have a thick cuticle better adapting them for drought tolerance.[8]
Dillenius' introduction of the term 'Pelargonium' inHortus Elthamensis 1732Pelargonium inquinans, (Geranium Afric. arborescens),Hortus Elthamensis
Pelargonium is the second largest genus (afterGeranium) within thefamilyGeraniaceae, within which it issister to the remaining genera of the family in its strict sense,[9]Erodium,Geranium, andMonsonia includingSarcocaulon. The Geraniaceae have a number of genetic features unique amongst angiosperms, including highly rearrangedplastidgenomes differing ingene content, order and expansion of theinverted repeat.[6]
The namePelargonium was first proposed byDillenius in 1732,[10] who described and illustrated seven species of geraniums fromSouth Africa that are now classified asPelargonium.[11][12] Dillenius, who referred to these seven species with apparent unique characteristics asGeranium Africanum (African Geranium)[13] 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’).[14] The name was then formally introduced byJohannes Burman in 1738. HoweverCarl Linnaeus who first formally described these plants in 1753 did not recognisePelargonium and grouped together in the same genus (Geranium) the three similar generaErodium,Geranium, andPelargonium.[15] Linnaeus' reputation prevented further differentiation for forty years.[12] The eventual distinction between them was made byCharles L’Héritier based on the number of stamens or anthers, seven in the case ofPelargonium. In 1774,P. cordatum,P. crispum,P. quercifolium andP. radula were introduced, followed byP. capitatum in 1790.[16][11]
Pelargonium is distinguished from the other genera in the familyGeraniaceae by the presence of ahypanthium, which consists of anadnate nectar spur with onenectary, as well as a generallyzygomorphic floral symmetry.[6]
De Candolle first proposed dividing the genus into 12 sections in 1824, based on the diversity ofgrowth forms.[17] Traditionally the large number ofPelargonium species have been treated as sixteensections,[7][18] based on the classification of Knuth (1912) who described 15 sections,[19] as modified by van der Waltet al. (1977–1997) who addedChorisma,Reniformia andSubsucculentia.
All subdivision classifications had depended primarily on morphological differences till the era ofphylogenetic analyses (Price and Palmer 1993).[9] However phylogenetic analysis shows only three distinctclades, labelled A, B and C.[20] In this analysis not all sections weremonophyletic, although some were strongly supported includingChorisma,Myrrhidium andJenkinsonia, while other sections were moreparaphyletic. This in turn has led to a proposal, informal at this stage, of a reformulation of the infrageneric subdivision ofPelargonium.
In the proposed scheme of Wenget al. there would be twosubgenera, 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),[6] 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 andHoarea) but paraphyly in others (Jenkinsonia,Ciconium,Peristera). A distinct clade could be identified within the paraphyleticPolyactium, designated sectionMagnistipulacea. As a result,Polyactium has been split up to provide this new section, which in itself contains two subsections,Magnistipulacea andSchizopetala, following Knuth's original treatment ofPolyactium as having four subsections.[6]
Thus Röschenblecket al. (2014) provide a complete revision of the subgeneric classification ofPelargonium based on four subgenera corresponding to their major clades (A, B, C1, C2);
SubgenusMagnipetala: Corresponds to clade C1, with 24 species. Perennial to short lived, spreadingsubshrubs, 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 andBotswana. Two species in East Africa andEthiopia. Chromosomes x=11 and 9.
SubgenusParvulipetala: 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.
SubgenusPaucisignata: 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 northernNamibia, with a few species in tropical Africa, Ethiopia,Somalia,Madagascar, theArabian Peninsula and Asia Minor. Chromosomes x=mainly 9 or 10, but from 4–18.
SubgenusPelargonium: Corresponds to clade A, with 167 species. Frequentlyxerophytic deciduous perennials with manygeophytes 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.[6]
Pelargonium has around 280 species.[4][20] Röschenblecket al lists 281 taxa.[6] There is considerable confusion as to whichPelargonium 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.[21]
One of hundreds of garden and houseplant cultivars
The namePelargonium is derived from theGreekπελαργός,pelargós (stork), because the seed head looks like a stork's beak.Dillenius originally suggested the name 'stork', becauseGeranium was named after acrane — "a πελαργός,ciconia, sicuti vocamus Gerania, γερανός,grus" (frompelargos, stork, as we call theGerania,geranos, crane).[22][14]
Pelargonium is a large genus within the familyGeraniaceae, which has a worldwide distribution in temperate to subtropical zones with some 800 mostly herbaceous species.[6]Pelargonium itself isnative tosouthern Africa (includingNamibia) andAustralia. Southern Africa contains 90% of the genus, with only about 30 species found elsewhere, predominantly theEast African rift valley (about 20 species) and southern Australia, includingTasmania.[6] The remaining few species are found in southernMadagascar,Yemen,Iraq,Asia Minor, the north ofNew Zealand and isolated islands in the southAtlantic Ocean (Saint Helena andTristan da Cunha) andSocotra in theIndian Ocean.[6] Thecentre of diversity is in southwestern South Africa where rainfall is confined to the winter, unlike the rest of the country where rainfall is predominantly in the summer months.[6] Most of thePelargonium plants cultivated inEurope andNorth America have their origins in South Africa.[21]
Pelargonium species are eaten by thecaterpillars of someLepidoptera species, including the noctuid mothangle shades,Phlogophora meticulosa. The diurnal butterfliesCacyreus marshalli andC. tespis (Lycaenidae), native to southern Africa, also feed onGeranium andPelargonium.[23]C. marshallii has been introduced to Europe and can develop into a pest on cultivated Pelargoniums. It has naturalised along the Mediterranean, but does not survive the winter in Westen Europe.[24]
TheJapanese beetle, an important agricultural insect pest, becomes rapidly paralyzed after consuming flower petals of the garden hybrids known as "zonal geraniums" (P. × hortorum). The phenomenon was first described in 1920, and subsequently confirmed.[25][26][27][28] Research conducted by Dr. Christopher Ranger with theUSDAAgricultural Research Service and other collaborating scientists have demonstrated the excitatory amino acid calledquisqualic acid present within the flower petals is responsible for causing paralysis of the Japanese beetle.[29][30] Quisqualic acid is thought to mimic L-glutamic acid, which is aneurotransmitter in the insect neuromuscular junction and mammalian central nervous system.[31]
A study by the Laboratory of Apiculture & Social Insects group at theUniversity of Sussex on the attractiveness of common garden plants topollinators found that a cultivar ofPelargonium × hortorum was unattractive to pollinators in comparison to other selected garden plants such asLavandula (lavender) andOriganum.[32]
Thegeranium bronze butterfly is a pest ofPelargonium 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 theEuropean and Mediterranean Plant Protection Organization and can cause significant damage toPelargonium species.[33]
Pelargonium triste, the first species of its genus to be cultivated, here shown in its native habitat inCape Town
Various types ofPelargonium are regular participants in flower shows and competitive events, with numerous societies devoted exclusively to their cultivation. They are easy to propagatevegetatively fromcuttings.[34][35][36] It is recommended that cuttings should have at least two nodes.[37] Zonal geraniums grow inU.S. Department of Agriculture hardiness zones 9 through 12. Zonal geraniums are basically tropical perennials. Although they are often grown as annuals, they may overwinter in zones as cool as zone 7.[38]
There was little attempt at any rational grouping ofPelargonium 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 botanistLiberty Hyde Bailey (1858–1954) introduced two new terms for zonal and regal pelargoniums. Those pelargoniums which were largely derived fromP. zonale he referred to asP. ×hortorum (i.e. from the garden), while those fromP. cucullatum he namedP. ×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 ofHenri 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 theInternational Cultivar Registration Authority (ICRA) of theInternational 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 indicateRoyal 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]
A. Zonal pelargoniums (Pelargonium ×hortorumBailey)
These are known as zonal geraniums because many have zones or patterns in the center of the leaves,[36] this is the contribution of thePelargonium zonale parent. Common names include storksbill, fish or horseshoe geraniums.[50] They are also referred to asPelargonium ×hortorumBailey. Zonal pelargoniums aretetraploid, mostly derived fromP. inquinans andP. zonale,[53] together withP. scandens andP. 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 ofP. inquinans.[16] Flowers may be double or single. They are the pelargoniums most often confused with genusGeranium, particularly in summer bedding arrangements. This incorrect nomenclature is widely used in horticulture, particularly in North America.[16]
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 exceeding165 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 exceeding90 mm (3+1⁄2 in) but not exceeding120 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 exceeding90 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]
(vii) Zonartic hybrids – Zonartic pelargoniums are a group of hybrids bred by Australian horticulturist Cliff Blackman. Hybridisation to establish this group began in 1985 through crosses between zonal pelargoniums (Pelargonium × hortorum) and the wild species Pelargonium articulatum. The name “Zonartic” derives from zonal and articulatum, reflecting this genetic combination. Blackman’s breeding programme produced a distinctive line of pelargoniums noted for their large, luminous flowers and for his effort to develop a true yellow pelargonium. Since then, Zonartic breeding has spread internationally, with active hybridisers in the United Kingdom, Sweden, Russia, and other countries. Breeders often identify their hybrids through a prefix; for example, Blackman used the prefix ‘Lara’ for his cultivars.[57]
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 andP. quinquelobatum.[50]
B. Ivy-leaved pelargoniums (derived fromPelargonium peltatum)
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 speciesP. 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'.
These are large bush-typefloriferous 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.
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.
D. Angel pelargoniums (derived fromPelargonium crispum)
Angel pelargoniums are similar to Regal pelargoniums but more closely resembleP. crispum in leaf shape and growth habit. The majority of Angel cultivars originate from a cross betweenP. 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 withP. 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]
E. Unique pelargoniums (derived fromPelargonium fulgidum)
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 fromP. 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.
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 oilgeraniol, 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, havingP. 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]
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 areP. ×ardens – fromP. lobatum ×P. fulgidum (1810).P. ×glauciifolium – fromP. gibbosum ×P. lobatum (1822). Usually, but not always, primary hybrids are sterile.
Other than being grown for their beauty, species such asP. graveolens are important in theperfume industry and are cultivated anddistilled 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.[citation needed] Pelargonium distillates andabsolutes, commonly known as "scented geranium oil" are sometimes used to supplement or adulterate expensiverose oils. The oils of the scented pelargoniums containcitronellol,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 includeP. crispum and P. citronellum. Rose-scenteds includeP. graveolens and members of theP. graveolens cultivar group. Other species and cultivars with culinary use include the lime-scentedP. ‘Lime’, the lemon balm-scentedP. ‘Lemon Balm’, the strawberry-lemon-scentedP. ‘Lady Scarborough’ and the peppermint-scentedP. tomentosum.[82] Scented leaf pelargoniums have also been historically used as toilet paper by fishermen in remote places, such as the Minquiers.[83]
Inherbal medicine,Pelargonium has been used for intestinal problems, wounds and respiratory ailments, butPelargonium species have also been used forfevers,kidney complaints and other conditions. Geranium (Pelargonium) oil is considered a relaxant inaromatherapy, and in recent years, respiratory/cold remedies made fromP. sidoides andP. reniforme have been sold in Europe and the United States.[82]P. sidoides along with Echinacea is used forbronchitis.[84]P. odoratissimum is used for its astringent, tonic and antiseptic effects.[citation needed] It is used internally for debility,gastroenteritis, andhemorrhage and externally for skin complaints, injuries, andneuralgia andthroat infections. The essential oil is used in aromatherapy.[85]
ChemistJohn Dalton realized that he was color blind in 1794 when he heard others describe the color of the flowers of the pinkPelargonium zonale[88] as pink or red, when to him it looked either pink or blue, having no relationship to red at all.[89]
^The generic description ofPelargonium inHortus Kewensis was copied from L’Heritier’s unpublished manuscript titledCompendium Generalogium[2]
^It has been stated that the choice ofP. hirsutum was made arbitrarily,[3] and thatPelargonium cucullatum(L.) Aiton, designated by van der Walt[2] should be the lectotype species. Furthermore,P. hirsutum is not currently recognised as an accepted name.
^A. P. de Candolle; et al. (1824–1873)."Geraniaceae: Pelargonium".Prodromus systematis naturalis regni vegetabilis sive enumeratio contracta ordinum, generum specierumque plantarum huc usque cognitarum, juxta methodi naturalis normas digesta. Vol. I. Sumptibus Sociorum Treuttel et Würtz. p. 649. (also available online atGallica)
^Handlos, Wayne (2010)."The Sections of Pelargonium".Geraniums Online. Central Coast Geranium Society. Retrieved3 August 2017.
^Knuth, R (1912)."5: Pelargonium L'Hér.". InAdolf Engler (ed.).Das Pflanzenreich: regni vegetablilis conspectus (in German). Vol. 129: Geraniaceae. Leipzig: Engelmann. p. 316. Retrieved16 August 2014.
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