REGAL PELARGONIUMS - 2016   By Wayne Handlos, Ph.D.

   1.       2.      3.      4. 

1.-2. P. cucullatum (flower and leaf)            3.-4.. P. fulgidum (flower and leaf)

            5.            6.         7.

 5. Neerland’s Plantentuin 1865, v. 1    6. Dr. Neubert’s Garten-Magazin 1864, v. 17

                                                                                     7. Illustrierte Gartenzietung 1857, v. 1

8.    9.     10.     11.      12.

8.‘Cream ‘n’ Green’   9.‘Spanish Lavender’  10.‘Happy Mystery’ 11. ‘Fringed Aztec’ 12.‘Moonglow’ seedling

Someone has written that regal pelargoniums are the ballerinas of the geranium world. It is

not a great leap of imagination to see the similarity between a vibrant pink, frilly, ruffled regal

flower and a dancer’s tutu. And, in fact, of all the cultivated groups of Pelargoniums, the regals

have the largest, frilliest, most ruffled, most colorful and most elaborately patterned flowers of

all the Pelargoniums. They also have the longest history of cultivation. The earliest introductions

of Pelargonium species into Europe from the Cape area of South Africa included P. cucullatum

and its variants and close relatives. From these early beginnings have developed what were also

called Martha Washington geraniums, Lady Washington geraniums, show geraniums or just pelargoniums. 

The spectacular flowers of P. x domesticum, a name coined by L.H. Bailey for this desirable group

of hybrids with obscure origins, have led these plants to be sought after by growers from the dates

of their first introduction. The larger size of the flowers, the ease of propagation from seed and

cuttings, have made these plants easily accessible. Their major failing is their special temperature

requirements for flowering. This requirement has only made the plants more challenging. Flowering

is triggered by night temperatures of 55˚F and below. If night temperatures are warmer, flowering

stops. Therefore in most temperate climate areas these plants only bloom in the spring and spend

the summer in a green, vegetative state. In European areas with cool nights, flowering continues

for a longer period. Coastal areas of Central California and higher mountain areas (upland Ethiopia,

for instance) with lower night temperatures trigger floral displays as long as temperatures are suitably


It has been suggested that up to 24 species are involved in the ancestry of our current cultivars of

regals. This is unlikely to be true but is probably based on the fact that every variant grown in the

late 18th and early 19th centuries was given a Latin name and description. Without reading the

accompanying texts, one would be led to believe that each of these entities was a valid biological

species in today’s terms (i.e. found growing in nature). Andrews, Sweet, Trattinnick and von Reider,

important chroniclers of 19th century Geranium/Pelargoniums among others engaged in this practice.

 If a plant has a scientific Latin name, most people would view this as an indication that this plant

was a native species, found somewhere in the wild in its native setting. These authors tried to indicate

which plants were natives of South Africa and which were hybrids produced in a garden or greenhouse

in England, Germany or France through the intentional hybridization of different plants or inadvertently

aided by the meanderings of bees amongst diverse flowers. Sometimes the authors did not know the

origin of the plants they described, or were misled by growers who thought their seeds came from

South Africa, when in fact, they did not.

If you look at a copy of Sweet’s Geraniaceae (unfortunately an original, 5-volume set would cost you

upward of $15,000 but is easily available free on-line) you would be impressed by the diversity of the

flowers and the detailed Latin and English descriptions. The authoritativeness of this work remains

impressive today almost 200 years after its publication.

The colors of the flowers of regals cover the range from white, pink, scarlet, salmon, red, lavender,

purple, brown, almost black, with and without pigmented spots and veins on the petals. (No true

blue colors are found among the regals.) The ancestral species have prominent vein patterns on the

two upper petals; these may be elaborated or lost in various cultivars or found on the lower petals as

well. Amongst the variations found in the flowers, there may be two spots, five spots or none, a white

throat, veins on the two upper petals, veins on all five petals or no veins of contrasting colors, picotee

or white edged petals, ruffled, fringed, toothed or lobed petals, striated patterns. An additional petal or

two is commonly seen although semi-double flowers have been found and grown at different times. An

extremely double form has been found in P. cucullatum and can be found today in the cultivars ‘Golf

Ball’ and ‘Spanish Lavender.’ The flowers are usually zygomorphic with the two upper petals larger than

the three lower ones. Some cultivars have all petals of the same size with the resulting flower radially

symmetrical or actinomorphic. Leaves often have coarse, bristly hairs but may be smooth or softly hairy.

The leaf shape varies from round to variously lobed. Cucullatum refers to the cup-shaped or

hooded nature of some leaves. The leaf margin is usually toothed. In a few cultivars the leaves are

variegated with a white margin. Some of the ancestral species and early hybrids were quite tall (to

two meters/yards).

Regals are renowned for their floral colors and combination of colors which are not seen in any other

group of Pelargoniums. All the major flower pigments are found among the regal cultivars, frequently

with several in one flower. These include pelargonidin, cyanidin, peonidin, delphinidin, petunidin and

malvidin. The localized concentrations of pigments account for the varying intensity of colors in the

flowers. Reported inheritance patterns indicate that five spots are dominant over two spots. Pigmented

(colored) lower petals are recessive to colorless petals. Stature is also under genetic control. Even though

the most popular color of zonal geraniums is red, amongst the various species of Pelargonium red is not a

common color. Since red flowered P. x hortorum (zonal geraniums) do not hybridize with regals, the red

color had to come from some other species. The only other likely candidate with red flowers is P. fulgidum

which has the right chromosome number (2n = 22), was available and frequently grown in Europe from

1732 and is a promiscuous breeder. California has been one of the major centers for developing new cultivars

of regals in the 20th century. Unfortunately with globalization, geranium/Pelargonium breeding programs have

mostly moved to Europe and California’s contribution has declined. The contributions of the Oglevee firm

and David Lemon were significant to the regal Pelargonium world. While it has been suggested that many

species contributed to the development of today’s regals, this is probably not true. In the past, it was

thought that P. cucullatum, P. angulosum and P. acerifolium were the primary ancestors of regals. Modern

taxonomists consider these variants to be aspects of the same species, P. cucullatum. Subtract two from

the list of ancestors. Researchers have shown repeatedly that the crosses most likely to be successful are

between plants that have the same chromosome number. That would seem to eliminate a number of other

potential ancestors. Even though it has been suggested that several species contributed to the development

of the regal lineage, reports by various breeders seem to refute this idea. The barriers of incompatibility have

 indicated (as many have found) that interspecific crosses are not so easy to make. Among the various other

species suggested as potential ancestors of regal are: P. betulinum (birch leaved), P. grandiflorum (large

flowered), P. capitatum (rose scented), P. cordifolium (heart leaved), P. fulgidum, P. scabrum (apricot),

P. graveolens (rose geranium). It is unlikely that the rose-scented, apricot, and rose geraniums had any

influence on the ancestry of regals because of the vastly different chromosome numbers. P. capitatum has

diploid numbers of 54 and 66 and is not a frequent hybridizer as noted in a list of hybrids in The Pelargonium

Breeder. P. graveolens has diploid numbers of 72, 88, 90 and 144. P. scabrum (probably Apricot or ’Paton’s

Unique’) has 2n = 36. So the species with the same basic chromosome number would be those with 2n = 22;

P. cucullatum, P. betulinum, P. grandiflorum, P. cordifolium and P. fulgidum. The early hybrids would most

likely have been diploids with 2n = 22. It is reported that regals are also tetraploid with 2n = 44. Once this

was achieved then cross breeding with other species becomes more likely and then such species as

P. quercifolium, P. crispum and P. citrosum (probably P. citronellum) with 2n = 44 becomes a possibility.

One investigator has been able to produce a triploid regal with 2n = 33. Other numbers reported for

regals include (17, 18,) 22, (35, 36,) 42, 43, 44 and 45. The number 17 and 18 may represent the haploid

state, while 35 and 36 probably represent the triploid level. Apparently at the tetraploid level, the loss or

addition of a chromosome or two is not lethal and many help explain some of the sterility that is commonly

seen among the cultivars. Unlike some other plant groups the barrier between diploids and tetraploids

among the Geraniaceae has not resulted in many triploids (apparently). Unfortunately a comprehensive

survey of the cultivars for their chromosome number has never been made so we just don’t know

An English breeder, E. Walters began using the species with 2n = 44 to extend the flowering season

and reduce the stature of the regals in his Romany, Royal and Tudor lines. This technology was ultimately

transferred to the Oglevee Corporation for the production of their lines of regals.

On a cultural level, regals, like most other Pelargoniums, require well-drained soil or potting mix. They

will tolerate some frost but if the stems are frozen new plants may sprout from root buds. If the cultivar

is a chimera the resulting plant may not look like the original. A number of cultivars of regals are notorious

for "reverting" or "sporting". This is due to their chimeral nature where different cell layers are genetically

different and flower color depends which layer gives rise to the epidermis where the flower pigments are

 expressed. The other major problem with regals is their susceptibility to white fly infestations. Some

cultivars are more resistant than others, but poor nutrition, crowding of plants and foliage, and high

humidity levels make the problem worse. The importance of good organic soil cannot be over emphasized.

Bud worms are not a problem.

Regal Pelargoniums remain a much loved group of cultivars despite their special requirements for

blooming and frequent infestation of white flies. The International Regal Preservation Project

encourages the cultivation of heirloom varieties to keep them from extinction. (See link in border on left)   

Beauty overcomes all.

© 2016, Central Coast Geranium Society (CCGS )