The Yellow Light at the end of the Tunnel

The possibility of breeding a yellow Pelargonium cultivar has been on the wish list of many growers and breeders ever since the red flowered zonal “geranium” became popular in the 19th century.

The Lara zonartic hybrids that are shown here are some of the results during 22 years of breeding with hybrid plants that were initially raised from crosses of a zonal or a zonal/ivy cultivar as the seed parent and the species Pelargonium articulatum as the pollen parent. There have been many interesting flower forms and colours produced from this line of breeding. This is possibly the first occasion that this species has been used for hybridizing with zonal varieties or other species.


Pelargonium articulatum is indigenous to Southern Africa. This pelargonium species is “characterized by an underground rhizome consisting of alternating thick and thin portions”. Generally there is little stem growth above soil level. It has a deciduous nature – with early leaf senescence, which is very unappealing at the time the flowers are blooming. The pale yellow flowers are attractive; the few flower stems produce only 2 to 5 florets each and the flowering season is rather brief. These yellow flowers are the main attraction for breeding with this species, although the short nodal distance and the mild leaf scent are possibly useful characters. The deciduous nature is of doubtful benefit. There are other characters that are not suitable for breeding purposes such as the long thin petioles that tend to let the leaf blades droop. This is the growth behaviour when container grown in captivity far away from its natural habitat.

When a species such as Pelargonium articulatum has been combined with a zonal cultivar or a zonal cultivar that has an unknown percentage of ivy pelargonium genes in its lineage, there is a great deal of uncertainty about what the resulting hybrids will be like. In 1985 when the first cross-pollinations were initiated the main interest was whether there would be any yellow in the flowers from the contribution of the 50% articulatum genes.

This first hybrid seedling was raised in 1986. Their composition was 50% zonal & 50% articulatum. The resulting flowers were single and white with a pale reddish blush on the upper petals.

These are another 3 of the 1986 original hybrid seedlings. They were partly deciduous; their form and habit is about midway between the parents. They have a non-symmetrical form and very irregular branching. The fact that articulatum did combine with a zonal type cultivar to produce a new hybrid breed was itself an exciting development.

The method of plant breeding that has been used during this period is the selection of the parents and the controlled transfer of the pollen onto the stigma of the intended seed parent and of course raising the seedlings.

Any progeny of the plant world will have inherited half of its genetic make up from each parent. This combination of both parent’s genetic heritage will generally produce plants that are mid-way between the appearance and habit of the parents, though sometimes there can be a dominance of habit inherited from either one of the parents. This factor becomes more apparent when there are numerous hybrid seedlings raised, as it is then possible to compare the visual differences of the form, flowers and growth habit. Up to the present date there has not been two of these hybrid seedlings exactly alike; in fact they all have a unique individuality that is demonstrated by their visual differences.

In the year of 1987 several hybrid seedlings with (25% zonal and 75% articulatum) in their composition were raised; the best of these had single pale yellow flowers that faded in a few days. During the following 7 years, there were many hundreds of these hybrids raised with varying percentages of zonal and articulatum in their composition. The year 1993 gave a start to changes and improvement in the flower form & colours. The year 1994 produced the first semi-double yellow flowered hybrid 94171 but this had a much too high, almost 80% of Pelargonium articulatum in its composition that gave this seedling an irregular form. However this was a significant step towards developing a desired yellow flowered cultivar and did confirm that the yellow in the flowers of articulatum can be inherited by its hybrid offspring.

The flower of 94171 has about the same colour as the flower of species P. articulatum lineage chart.

Lineage chart

   Click to explore the chart

This is part of the Zonartic Family Tree, showing the line of descent to seedling 94171 – the first semi-double, yellow zonartic. Three of the originating parents are at the top of the Lineage Tree. ‘Lara Purnal’ – ‘Princess Fiat’ and ‘Millfield Gem’. Then two seedlings from combinations of these parents: ‘Lara Classic’ and ‘Lara Polka’ were crossed with P. articulatum the pollen parent in November 1985. ‘Lara Signal’ was used later. These are the original ingredients of the Zonartic hybrids. If you follow the line of descent to 94171 you will notice that articulatum is introduced into the line 6 times during that period, also when it was used as a seed parent or pollen parent. The seed parent is always shown on the left side of the combination.

The coined name zonartic

It was about this year, 1994 that the name of ‘zonartic’ was coined; this name was made up from the ‘z-o-n’ of zonal and the ‘a-r-t-i-c’ of articulatum, forming the name ‘zonartic’. [The name of ‘Lara’ had been accepted and registered as a plant breeder’s prefix about 1976].

At this point in 1994 it was briefly thought the development of a yellow flowered commercial cultivar was possibly just around the corner, but then; because of the form and habit of these hybrids which do include some unwanted characters inherited from species articulatum – it was soon realized this could be many years away. However the arrival of the semi-double yellow flower with 9 to 11 petals was a big improvement on the appearance of the yellow flowers and was definitely an encouragement to continue on the journey.

There was no quick way to improve the form and at the same time produce seedlings with yellow flowers. Each year the parents for the next years seedlings were selected to produce hybrid plants that could possibly have yellow flowers, but seeking to have a minimum percentage of articulatum that is needed to obtain this result. The percentage of articulatum has been a useful reference point in the selection of parents. With these hybrids the different percentages of this species and the zonal parent proportions in each individual seedling can produce quite different forms – also that a high percentage of yellow genes are necessary to produce seedlings having yellow flowers. With the early combinations they generally required at least 65% of this species. At that period the flower colour permanence was not as good. This has improved over the years by selecting for this habit.

Another direction being used at the same time was to select parents to work towards an upright symmetrical form and habit, but having a maximum percentage of articulatum in its composition that will allow this result. The seedlings of the two directions were often selected and combined for the following generation of seedlings.

During the process of endeavoring to obtain a suitable yellow flowered cultivar there were many surprising and welcome spin-offs. The year 1993 was the beginning of this period when there were very surprising and appealing changes to some of the flower forms and colours including bi-colours and tri-colours, also the individual flowers were larger on these hybrids than previously seen on the average zonal cultivar. This development was rather fascinating and did broaden the overall objective to include working towards any of the new flower forms and colours that were on the increase. But here again there was always a need for a better plant structure and habit.

Because of the necessity to change the plant form to a more symmetrical and upright structure it was found beneficial to introduce more of the zonal influence into the zonartic line and at the same time try to maintain the yellow flowers.

Selection of the parent plants is one of the most important requirements in the desire for getting improvements or decreasing any of the unwanted habit. Of course when there are multiple changes required, as is the case with the hybrids of articulatum – a change does sometimes go one step forward with the flower colour but one step back with the petiole length or early leaf senescence or plant structure or the size and number of florets. There are so many characters that can be affected by the large gene pool that have been inherited by these hybrids, any of which can influence the resulting seedlings in this ongoing development process – possibly some of these characters are linked, making it more difficult to separate the wanted features that go into the make up of a new range of cultivars.

The whole exercise of breeding and hybridizing plants is basically by taking advantage of the opportunities that nature can and does offer. The process can be assisted by creating a situation or condition that gives this possibility a chance to happen. This may be considered to be just a trial and error procedure and to some extent it is because this is unknown ground and can only be travelled by anticipated results, possibilities, choices and selections in a methodical regime.

When attempting cross-pollinations and also when trying for a reciprocal cross of the selected parents it is often necessary to repeat many of the same crosses to obtain viable seed. There is always a possible failure because of an incompatible factor with what are otherwise normally fertile cultivars. For this reason it is important to also use several similar pollen or seed parent alternatives that are mutually fertile to get positive fertilization results that will produce seeds that may include some with the required changes. The more seeds that can be obtained from suitable parents will certainly increase the chances of raising new plants that have the desired improvements.

There are a series of interesting times and exciting moments in the basic process of producing hybrid seedlings. The first in this cycle of events would be whilst making the cross pollination of the chosen parents. Usually within 24 to 48 hours the first indication of a successful fertilization is seeing the petals fall, the five arms of the stigma sometimes close together and the sepals close around the style, then usually after 4 or 5 days the ovarian beak commences to elongate. About 4 to 5 weeks later the harvesting of the ripened seed gives hope for the dream about the possible results. The first week in February is usually the time to start sprouting the new generation of seedlings – weather permitting! Two weeks later the majority of the sprouted seeds will have been transferred into small pots. There is not a long waiting period to observe any form change or petiole length reduction – as there are indications of these changes during the first 2 to 4 months of growth. After about 9 or 10 months from sprouting it is flowering time, this is certainly the most exciting period in the yearly breeding cycle – the culminating moment of the year’s hopes and the wonderful feeling when sometimes seeing a new and beautiful flower opening up. It is always more exciting if being seen for the first time. Each new creation follows with opportunities for attempting other creative combinations.

One of the more interesting outcomes has been the appeal of the flower forms and colours. Their longer pedicels can give a more open form of inflorescence, also the unusually long flower stem and their lasting quality has made some suitable for use as cut flowers.

To summarize with 7 essential ingredients for this journey would include:

  1. Having a plant of P. articulatum #1571A from Stellenbosch in 1984 – this was kindly given by Dr. Piet Vorster.
  2. The natural forces that are part of the creative environment are a necessary element in life’s many processes.
  3. The ability of articulatum to combine with zonal type pelargonium cultivars when using controlled cross-pollination techniques.
  4. Having hybrid progeny that are fully fertile and which are compatible with self-pollinations and new combinations with seedlings and parent plants of this new family.
  5. Making sure all of the lineage and photographic details are recorded.
  6. Having perseverance, time and luck with an overwhelming interest in the whole procedure.
  7. Last but not least, a tolerant and encouraging wife.


Gallery of Zonartic hybrid varieties in chronological sequence:



























Enjoy more Zonartic in this article!


by Cliff Blackman, Victoria, Australia

April 2009

All images are © the photographer.

(From the presentation to the International Pelargonium and Geranium Conference, October 2006, Geelong, Australia.)