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Hybridization between planted Proteas and their cultivars with wild Proteas: The Frankenflora


It has been suggested that based on the presence of man-made hybrid swarms in the Cape Flora, care should be taken in the planting of species outside of their home ranges.

At present the following have been detected:

  • Massive Protea lepidocarpodendron-neriifolia hybridization at Silvermine resulting from use of P. neriifolia as a rehabilitation species in the Ou Kaapse weg road gravel pits within a natural population of P. lepidocarpodendron.  Similar hybrids appear on the Rooiels-Betty’s Bay road verge rehabilitation where P. neriifolia was incorrectly transferred into P. lepidocarpodendron habitat, and where P.neriifolia is being grown at Harold Porter near P. lepidocarpodendron stands, but the impact of this is appears to be minimal (small areas, small numbers).
  • Hybrids between Proteas lepidocarpodendron, neriifolia, burchellii and laurifolia below Tafelberg road on  Table Mountain .  It is not possible to easily determine which species are contributing to the hybridization, but it is suggested that P. burchellii is the major culprit.
  • Hybrid swarms at Helderberg Nature Reserve between the planted White Proteas (P. aurea, lacticolor, mundii, and punctata) expanding into natural veld following the previous fire, with similar intermediates present at Kirstenbosch, Harold Porter, Van Staden’s Nature Reserve resulting from seedling recruitment in the flower beds.
  • Following a fire at Salmonsdam Nature Reserve, many species naturalized either in the burned specimen beds or in the adjacent veld.  Some 11 obvious hybrid combinations were detected among the plants, mainly between White Proteas, but also involving P. susannae.  No detailed tests were done so there may have been more.

A potential problem thus does exist.  However, apart from White Proteas, P. lepidocarpodendron-neriifolia crosses, P. susannae, and the highly promiscuous P. longifolia and P. burchellii, there is as of yet no reports of serious hybridization between planted proteas and natural populations.  However, no rigorous surveys for hybrids adjacent protea orchards, city-fynbos interfaces and adjacent rehabilitation projects has ever been undertaken.  The potential problem applies to related species that have non-overlapping ranges and that are thus unlikely to have evolved incompatibility mechanisms.  It is compounded among these closely related species in that they look similar to one another and identification – even by experts – is often based on geographical location.  Whereas hybrids are relatively easily noted in the field when both parents are present, in the herbarium or when one of the parents is extinct (e.g. the planted plants have died), such plants are often noted as sports or extreme variants of the expected species.

The following groups (within the Proteaceae) might be expected to be especially vulnerable to hybridization, but further studies are required to confirm that this in fact the case:

  • Spoonbract Sugarbushes

  • White Sugarbushes (confirmed!)

  • Penduline Sugarbushes (not widely planted)

  •  Rose Sugarbushes (not widely planted)

  • Eastern Ground Sugarbushes (not widely planted)

  •  Pin Spiderheads (not widely planted)

  • Stalked Spiderheads (not widely planted)

  • Curly Spiderheads (not widely planted)

  • Paw Spiderheads (not widely planted)

  • Skirted Spiderheads (not widely planted)

  • Common Scepters (not widely planted)

  • Elongate Scepters (not widely planted)

  • Wide-tubed Pincushions

  •  Fireworks Pincushions (not widely planted commercially)

  • Showy Pincushions

  • Louse Pincushions (not widely planted)

  •  Flat Pincushions (not widely planted)

  • Sandveld Pincushions (natural hybrids recorded at periphery of ranges)

  • Silver Pagodas (not widely planted)

  • Tube Pagodas (not widely planted)

  • Arid Conebushes (not widely planted)

  • Sandveld Conebushes (not widely planted)

  • Silver Conebushes 

  •  Sun Conebushes

  • Crown Conebushes (not widely planted)

  • Delta-seed Conebushes

  • Clay Sunshine Conebushes (not widely planted)

  • Broad-leaf Sunshine Conebushes

  • Discolor-group Sunshine Conebushes

  • Needleleaf Conebushes

Consequently, it has been suggested that NEM:BA should list White Proteas as “Category 4” invaders. See a full list of Proposed Category 4 species in terms of NEM:BA.


Most protea growers have not detected any hybrids

I do not expect many protea farmers and pickers to be able to identify hybrids in the field.  Firstly, 95% of those growers with orchards don’t go look in the field.  Secondly, any hybrids will only appear after a fire, and after 6 years of no flowers following the fire, who will remember what the original wild plants in the veld looked like?  Thirdly, some of the hybrids are very hard to identify.  And lastly, would any commercial protea growers admit to something that might get them and the industry into trouble?

That does not mean that hybridization doesn’t occur.  So at Helderberg (and Kirstenbosch, Harold Porter, etc.) there is a total mishmash of White protea hybrids.  Basically all the White Proteas occur in non-overlapping ranges, and when they are brought together, they do not appear to have any mechanism to stop hybridization.  The same is probably true of many other groups (see above, but especially the Sun Conebushes, Delta-seed Conebushes, Showy Pincushions, Wide-tubed Pincushions and Spoon-bract Proteas, which are grown commercially).  Atlassers recorded lots of hybrids after a fire went through the "specimen garden" at Salmonsdam Nature Reserve (why the reserve manager needed to bring examples of proteas from the entire Kingdom to plant in a nature reserve for heaven knows, but the same can be found at Silvermine, Helderberg, Bontebok and other “nature reserves”).  So hybridization does occur.  Sometimes one does not know if what one is looking at is normal plants or hybrids:  For instance at Doringrivier in the Riviersonderend there is a funny form of very narrow-leaved Protea repens - alongside an abandoned protea orchard: is this hybridization with P. longifolia or just a local form? At about R1000 in lab materials to resolve this conundrum using DNA, it is not worth the effort.

Hybridization is natural and occurs in nature.  Why should we be bothered?

Hybridization is not normally a problem (Pr longifolia and Pr burchellii excepted) in the wild, as species that occur naturally together have evolved means for preventing hybridization. The problem is when species that have never met are brought together: then hybridization is a major problem.  The Cape Flora is characterized but a high species richness.  This is partly due to turnover of species between small geographical areas.  Commercial and urban growers do not respect these boundaries and thus bring together species that would never naturally have met.

A further problem is that of local races.  Many of our species have local populations that are adapted to local conditions.  Thus Marie Vogts recognized 82 varieties of Protea cynaroides.  It would be foolish to allow all these to hybridize for two reasons.  Firstly, some of the hybrid populations will be unfit and result in local extinction, which we do not want.  Secondly, this variation is the crucible of evolution within the Cape Flora: both conservationists and horticulturists should want to preserve this variation to ensure the future of species and as a source of horticultural genes.

But many of our diverse species are just relicts about to go extinct anyway.  Why worry?

Please prove to me that Orothamnus is a relic. It could just as easily be argued that it is a species adapted to cool, misty slopes and peaty soils – that it is a highly adapted, specialized species, not some out of date fossil, hanging onto its last cliffs by the skin of its roots. It is also the most recent of the Mimetes species, a new specialist.  It is rare because it is specialized to a rare habitat.  What is wrong with that? - Protect its habitat and it will be fine!  Besides, even if it was a relict I would want to protect it - no senile, ancient, relict argument will convince me that we should let it go extinct because some farmer might lose a nice profit.  How many of our 9000 species should we ignore because we have “too many” or because “they are relicts”?  Answer: None!  They are what makes the Cape Flora unique!

But Marie Vogts planted many species at Kogelberg and we have no problem there!

But: Who did the study of the natural forms in the Kogelberg and Paardeberg before she did her studies?  There could be major genetic contamination there and you and I would be none the wiser.  We can do a study of the strains and morphotypes present there now, but without a background study before she started we can do nothing.  Except at R200 per sample we could use DNA: that will shed light on the story, but we do not know which strains she planted and how many of each, so that it would be very expensive to try and get DNA from the variants she brought in (unless some of Marie's descendents are billionaires, but how might we prove that she was aware of the problem and therefore negligent?).  With cultivars that source DNA is easy to get, and the only problem is cost.  As for negligence, the industry has now been warned!

But birds have always moved pollen around.  Why worry about a natural process.

Of course the birds fly.  But how often do you go to George in your daily activities?  Same with the birds: they sit in their territories and fly to water (the bar?), and fly to other water for a bath (the spa?), but while there is food at any one place they defend their territories and seldom move even a few hundred metres (even to get to the bar and spa) for weeks.  So there is no way that Sugarbirds or Sunbirds will take pollen from a protea on the Langeberg to one on the Swartberg or Potberg.  BUT THEY WILL TAKE IT FROM THE ORCHARD TO THE VELD!  So a very bad example to use, unless of course one advocates killing the birds that visit the orchards ....  But we know where that will get us.

Why do you single out cultivars as a problem?  There is no evidence that they hybridize with wild plants?

Cultivars usually are derived from hybrids.  If those hybrids are fertile, they stand a very good chance of backcrossing with their parents and a better chance than their parents of crossing with relatives.  If fertile hybrids are moved into areas where relatives occur they will result in genetic contamination, ranging from minimal to catastrophic.  It is a potential problem and it wont be resolved by cunning arguments and denying that there is a problem.  Remember we are talking pollen fertile, not seed fertile, plants.  I do not suspect that seed-derived contamination will ever occur in orchard situations, where farmers remove old flowerheads before they set seeds.  However, no one has ever checked for genetic contamination.

Checking up on genetic contamination is not difficult at all.  It is just very expensive if you want to go the DNA route - and the courts will probably demand it.  We know it exists, we know it is potentially a disaster that can result in local extinction, but what we don't know is how prevalent or problematic it is, and if cultivars are especially much of a problem.  At this stage all we are suggesting is that pollen-sterile cultivars would be acceptable, but that those with fertile pollen should be monitored.

Why are you trying to close down the South African Protea Industry?

At present all I am recommending is that White Proteas and Protea longifolia and P. susannae -and their derived cultivars - are not planted outside their home ranges within 2-5 km of any natural populations of those species with which they are known to hybridize.  More than that I cannot justify.  But if other species are found to be hybridizing then they will in due course be added.  And if any cultivar starts proving a problem, then the fat is in the fire, and wholesale restrictions will not be far away.  I do also feel though that I must warn the industry that it is a potential problem that might shut down the industry unless they start applying more rigorous standards to ensure that it does not happen.  These include developing pollen sterile cultivars, self policing to try and prevent any potential problem from arising, and a far more careful approach to what species are introduced to orchards in and adjacent natural areas.   It will only take a single case of bad genetic contamination for a total ban on the industry until it can prove that it is safe.  It is up to the industry to ensure that that first case never happens. (and we won't go the route of what might happen if it tries to cover up any cases ...)

Surely in this cut-throat world it is survival of the fittest?  We must first and foremost protect the industry and the jobs and income it provides.

As you said "survival of the fittest".  And in our new environmentally friendly world view, just make sure that protea growers are not the old fashioned dinosaurs, one step away from extinction.  In a changing environment you need to be proactive and aware, careful and cutthroat, transparent and surfing the crest of the wave.  Don't pretend that there is not a problem. Don't fool yourself that hybridization is natural and will go away when you close your eyes.  It is time for the industry to start setting up guidelines so that when that fateful day arrives when someone discovers a major genetic contamination, you can point out that it would not have happened if the grower in question had followed industry guidelines.

National Parks is being called to task because of hybridization resulting from the revegetation of a land fill 40 years ago, and they have only been in charge for 5 years.  The Cape protea industry has the Achilles Heel that protea growers elsewhere in the world may benefit from the demise of the local industry if such a problem arises - they do not have any problem at all with the issue of hybridization because they do not have to protect the original species = we do.

You know I support the industry.  But if the industry threatens our flora then it must adapt or die.  The industry must not moan about the potential loss of jobs and then go away and pretend that the problem does not exist.  It exists - it is up to the industry to prevent the loss of jobs by ensuring that the potential problem will never materialize. The industry must not attack those who are identifying a potential problem – it should rather try and get a handle on how potentially bad the problem can become and determine needs to be done to prevent the disaster from ever being realized.


This is not a problem confined to Proteas.  There is concern that, for instance, the cultivation of Natal forms and subspecies of Bitou (Chrysanthemoides monolifera rotundata) by municipal horticulturists and private landscapers in Cape Town will hybridize with and eliminate our own Chrysanthemoides monolifera monolifera.  There is also a problem with specimen gardens of Ericas in nature reserves.  Bulbs and ornamentals are also a problem!  At least we are now aware of the problem – what we need now is to document how bad it is.  I suspect that when we look properly we will be seriously alarmed, although is it probable that only a relatively few plant species will be found to be seriously affected.  Alas there are commercial interests that do not want the problem to be investigated: money and jobs are at stake.  But there are also commercial opportunities for preventing the problem of genetic contamination and loss of biological diversity.  We can live sustainably with our flora – we must!

Tony Rebelo

June 2005

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