eduart zimer - (sdu) - adventive plants - part 7 (2009)

Succulent plants from down under Adventive Plants (Part 7):

The succulent corner at Yankee Wharf, Rangitoto A new Aeonium natural hybrid in New Zealand? (Notes on Aeonium Rangitoto - I)

XVII. The succulent corner at Yankee Wharf, Rangitoto (1)

Well, after the huge disappointment to see the Islington Bay Aeonium colony decimated by the Department of Conservation (see E. Zimer, 2009a) we had to decide what to do next. The main purpose of the January 2009 trip to Rangitoto was to take as many pictures as possible and to try to catalogue somehow the existing Aeonium forms existing in the small colony just south of Islington Bay wharf, but now all our hopes went off in flames. The sight was simply depressing all bigger plants with distinctive features have been removed; I was so upset that I simply left the site. Ironically, we have found our other target of the day the Agave americana colony halfway between the Islington Bay wharf and the passage to Motutapu Island also being checked and depleted from almost all bigger plants. A third objective the Wreck Bay, a place where several obsolete vessels were sunken or abandoned ashore until late in the WW2 years was only of moderate interest as far as I am concerned. We simply have lost a lot of time crossing the island for nothing. At least thats what I thought.

Fortunately Rangitoto is not a place to get easily bored or impatiently wait for the next ferry (except when youre running out of water) so that my younger son Vlad (my companion during the Rangitoto trips) and I took the decision to move rapidly back to the southern parts of the island in order to have a closer look at some other hot spots we havent visited before like Kidney Fern Glen, Kowhai Grove and McKenzie Bay and if time allows to have a quick run to Wilsons Park the remnants of an intended botanical garden, which reportedly

1. A wonderful Nerium oleander in flower halfway between Islington Bay wharf and Yankee Wharf.

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has also included few cacti and other succulent plants. It was still enough time for all of this we thought. Luckily we didnt decide to return to Rangitoto Wharf on the same route we came here, on the Islington Bay Road, faster indeed but less attractive for people with browsing habits like us but took the narrow coastal track instead. It proved that was in fact the best decision we could possibly take, even if we missed all other targets set for the day and nearly missed the last ferry to Auckland as well.

Ten minutes later and we have already reached Yankee Wharf. Just a short distance south of this place we didnt fail to notice the high concentration of succulent and non-succulent naturalized plants in this area not a high number of species, but a large number of plants scattered along the rocky shores, literally thousands of them from seedlings to well established individuals in places where the young pohutukawa (Metrosideros excelsa) bush doesnt come right to the waterline leaving larger areas of exposed lava fields. This kept us busy for most of the time we still had to spend on the island.

You cant miss this succulent hot spot if you take the eastern coastal track south. One of the first signs that you are close to the succulent hot spot is a magnificent Nerium oleander on the right side of the track, not a succulent plant but still a beauty when in flower. And standing out from the usual pohutukawa dominated vegetation anyway. From here on there are just few more minutes to go. There is a high concentration of Agapanthus praecox ssp. orientalis here, both white and blue flowering forms (2), simply infesting the area which immediately draws your attention from the distance. This extremely invasive plant thrives here apparently undisturbed and unharmed in recent times by the Department of Conservation (probably still concerned about the Agave americana and Aeonium colonies just a bit north) and spreads its seed all over the place creating in few corners a cover of young seedlings as you can see in some of the pictures.

There is no proper soil here but lava flows with pockets of sand or shingle; lichens are almost everywhere, very abundant in certain areas, and also organic debris or semi-decayed organic matter accumulates between and under the plants. In some places there rock has been apparently quarried leaving certain amounts of grit and

2. The site south of Yankee Wharf with Motutapu Island beyond the shallow waters of the channel. You can see the predominance of the white flowering Agapanthus praecox ssp. orientalis in this area.


finer particles. In some places even 5 or 10 meters from the shore the lava blocks are covered with a thin layer of shingle and shells possibly brought in by storms or maybe by land works. The entire place looks exposed but is quite sheltered actually even if close to the waterline the calm shallow waters of the narrow channel between Motutapu and Rangitoto islands have a very low dynamic and certainly do not provide full on marine exposure. Somewhat higher grounds protect also the area from east and west.

The only native succulent we have seen here was the halophyte chenopod Sarcocornia quinqueflora ssp. quinqueflora. It does not form massive population as elsewhere in Rangitoto, but still small tussocks are scattered here and there, within or near the splash zone. A very distinct feature of this plant is that it creates different growth forms depending on the amount and frequency of the seawater it usually gets. In places where

3. The splendour of the pure white flowering head of Agapanthus praecox ssp. orientalis. Many thousands of seedlings of this prolific seeder are scattered everywhere simply infesting the area and posing a major threat for adjacent parts of Rangitoto. I trust you have also noticed the tiny Crassula multicava and Crassula tetragona ssp. robusta plantlets hanging on to the lava block in the background.

4 5. Two slightly different growth forms of Sarcocornia quinqueflora ssp. quinqueflora.


the tide moistens the substrate (it can be even partly submerged) the plants are stronger, usually greener, and with long erect or ascending stems; on rocks where it gets only mists of seawater on occasion Sarcocornia quinqueflora ssp. quinqueflora stays smaller and stems have a somewhat contorted look. For an inexperienced observer they may look like totally different plants. This is actually the only plant naturally occurring here, all others are naturalized succulents being dispersed in more or less distant times from human settlements.

The rest of the succulent plants growing here is a collection of former garden glories. In fact some of them you can still see in the mostly abandoned gardens around the baches. There is something that strikes you immediately the abundance of succulent plants and no immediate source of infestation. In fact, quite far from former human settlements the holiday baches, not to speak of the mainland - you definitely can see more alien succulent plants here than close to the obvious infestation sources. And a stunning addition generally it is not true for non-succulent garden plants. The lack of competition on these almost barren lava fields, possibly human activity and disturbances has encouraged this rather strange localized vegetation pattern.

Sedum album is not as common as it is in the abandoned gardens near Islington Bay wharf, but we still have seen few nice bronze coloured plants that have found the right place for them. Very easy to spot when in flower, I usually can hardly notice their presence otherwise.

Aeonium hybrids were also scattered everywhere, at least three distinct forms with obvious haworthii and undulatum parentage, mostly smaller plants and surprisingly many plantlets, some of them almost stemless and bearing only 2 cm wide rosettes. We havent seen any plants with flower remnants (the site must have been checked in the past) but the large number of apparently young plants makes me think that seed was dispersed here at some stage. I think it is very unlikely that only vegetative means of dispersal may have produced that many plantlets not to speak of the variety of forms. We also couldnt find here two of the very interesting forms seen in the Islington Bay colony one year before the forms being apparently very close to the true species Aeonium haworthii and Aeonium undulatum. We also couldnt find the Islington Bay natural hybrid I have provisionally named Aeonium Rangitoto (see further below the notes on Aeonium Rangitoto).

6. Sedum album growing on a spot with accumulations of shingle, sand, crushed shells and vegetation debris. I havent seen this plant growing directly on the lava blocks; apparently it needs a thin layer of rocky substrate to thrive.


7. Countless Aeonium hybrids (mostly smallish plants like these) are scattered everywhere, preferring the cracks, crevices and fissures of the lava blocks.

8. One of the very few bigger Aeonium plants. Probably due to the very harsh conditions they do not usually branch (excepting Aeonium haworthii). Although I havent seen here flowering plants seed seem to have been dispersed here at some stage.

9. Aeonium hybrid sharing with Aloe maculata the same fissure in the lava block. Both plants prefer this kind of substrate, especially Aeonium; Aloe maculata grows on occasion on flat rocky soils as well.


Yankee Wharf is definitely a play ground for invasive plants the best example is probably the next couple of plants. We havent seen Crassula tetragona ssp. robusta anywhere else on Rangitoto, but here and what a view! We couldnt believe our eyes when we first saw the dense layer of seedlings and young plants covering some areas. The word thickets would be a totally adequate description if we disregard the low height of these plantlets, but try to imagine them reaching the height of a mature plant! With several flowering plants in the area it is very probably seed that keeps the numbers up. On the other hand it is this kind of substrate offered in Rangitoto that boosts its growth; you can see it in cultivation plant a Crassula tetragona up on a pile of rocks or in a crack of a stone wall and it will thrive like nowhere else.

Crassula multicava is also very common, but not really taking over. Again, we are dealing here with a very invasive plant having an extremely high infestation potential. Although reportedly New Zealand plants do not set seed (possibly due to clonal propagation in early days of its cultivation) this plant has an even more efficient mean of dispersal. Bigger plants are prolific flowerers and when the flowers start to wither tiny

10 12. Crassula tetragona ssp. robusta is very abundant on this site, forming dense patches of young plants. Flowering sized plants are also numerous, some still bearing the withered remnants of the inflorescences. Despite the high density of plants Crassula tetragona ssp. robusta has just a much localized distribution and does not occur anywhere else Ive been in Rangitoto.


plantlets are formed in the axils of the inflorescence. Soon these become airborne and establish quickly in moist pockets skipping the difficult germination process.

13 14. The composite vegetation pattern display is very eloquent in this picture form the front to the background, on only a couple of meters, there are four distinct rows of plants: Crassula coccinea, Agapanthus praecox ssp. orientalis, Crassula tetragona ssp. robusta, and Aloe maculata. You can also see how the substrate changes over a very short distance (left). A fine specimen of Crassula multicava (below).


The once favourite of the cottage gardens Crassula coccinea, with its bright red inflorescences of long tubular flowers is still catching your attention from the distance this time of the year. Flowers have started to wither, but still you cant miss their bright red inflorescences. There are just few plants scattered here and there, some plantlets as well. It does very well in gardens in rich soil but as all succulent plants here it has to grow on lava blocks with barely any organic matter (mostly debris) accumulated in fissures and pockets.

15. The peculiar way of vegetative propagation in Crassula multicava plants is visible in this picture. It is also very interesting how the plant simply follows the trunk margins. Under the trunk organic debris accumulates and retains the moisture hence the vivid green plants in this picture.

16. A flowering Crassula coccinea with Crassula multicava plantlets scattered in the background.


Carpobrotus edulis does not cover large areas; it looks more like plants have switched to survival mode here. Lots of dead stems but also some active growth but not even close to the dense mats of crawling stems we can find elsewhere. Truth is that its preferred habitat the sand dunes or the back of the beaches is not available here, being forced to grow on bare rock. However, they seemed to find few spots with accumulated debris and semi-decayed organic matter where survival was possible. But as the black basalt lava blocks get extremely hot in high summer I think it is rather the heat these plants cant stand. Probably thats why it does not form the

17. The resurrection of a Crassula coccinea plant.

18. Succulent mix with a dead Agapanthus in the centre.


typical mats of vegetation but rather tries to mix with other plants in a very composite pattern as you can see from the picture.

Sedum praealtum ssp. praealtum does not form large groups, but rather scattered plants are seeking more for shade and shelter. One of the things we have noticed these plants do not occur usually in open spaces, but elsewhere where stronger plants have already established, in most of the cases at bush margins, but sometimes almost hidden between Agapanthus tussocks very abundant in this area. There are mostly medium sized plants and just very few plantlets pointing towards a vegetative reproduction this time. We have seen several times this plant during past trips in Rangitoto, but none of them was flowering. I actually have no idea how the flower looks like and it seems to be a rather shy flowerer.

Aloe maculata (aka Aloe saponaria) is also very common here and provides few very fine specimens. Generally, you wont find the emerald green long leaved plants you can see on occasion in some shaded gardens, growing in rich soils with plenty of water available, but ascetic individuals instead with short and red-brown coloured broad leaves, showing a very compact growth as a result of the exposure, intense sunlight and quasi-constant water deficit. No wonder that T. F. Cheeseman who mentioned the first naturalized plants in Remuera (Auckland) in 1883 has identified them as Aloe latifolia, a form with broader and shorter leaves now fallen into synonymy. However, there are few glorious plants to see! Surprisingly, the very young plants are extremely numerous in some corners. Aloe maculata can be propagated by seed (but it takes ages and is a painful process, Ive been through this) or rhizomes emerging nearby. However, in this case the plants have no real soil to protect the rhizomes from the harsh sun. There is also some distance between different plants; we havent seen here the clump usually formed by cultivated plants. More, some of the plants grow in funny places like cracks and fissures on elevated lava blocks, which rather points to seed dispersal than by vegetative means. I havent seen any flowering plants (here or in other parts of Rangitoto) but I also assume this site is checked from time to time by the Department of Conservation.

19. Carpobrotus edulis trying to survive extreme heat. This is one of the few spots here at Yankee Wharf where this plant seems to have somewhat established (although this is far from its normal density and growth pattern on sand dunes). Probably the layer of dead stems provides some protection from the lava blocks getting very hot in high summer and also retains precious moisture for a bit longer.


And last but not least Aloe arborescens the big bonus of this trip. I couldnt believe my eyes when I saw it first through the binoculars. This was such a surprise for us and quite a novelty I think the only Checklist on naturalized plants it appears on is D.J. Mahons Canterbury naturalized vascular plant checklist, version June 2007, as a casual occurrence in Banks Peninsula, recorded by Wilson in 1999 but its presence on Rangitoto

20. Sedum praealtum ssp. praealtum prefers sheltered positions between higher plants or dense patches of vegetation and with some accumulations of decayed organic matter.

21. Another Sedum praealtum ssp. praealtum plant between Agapanthus tussocks and with the usual Crassula multicava plantlets in the background.


wasnt mentioned at all before in botanical references so far I know. The only Checklist of naturalized plants I couldnt consult is the one published in 2008 in The New Zealand Journal of Botany, available only to subscribers. A couple of well established individuals, showing again a rather very simplified growth forms, quite different from the arborescent growth (hence the name) we can usually see in cultivated plants. Im a bit clueless about how these plants could get here and propagate.

22 23. Aloe maculata is very common at Yankee Wharf and provides the most spectacular specimens. The plant is shooting rhizomes but the rosettes do not stay very crowded as you can usually see in cultivated plants because of the scarcity of the moisture. All plants here have the red-brownish colour due to the exposed conditions and quasi-constant water deficit (left). An extra fine specimen, full of character, with extra short and extra broad leaves a living statement of what it had to endure (below).


24 25. Freely mixing: Aloe maculata with Crassula multicava (left) and Aloe maculata with Carpobrotus edulis (right).

26. One of the big surprises we had on this Rangitoto trip Aloe arborescens, never mentioned on Rangitoto in botanical or non-botanical accounts.


This site is quite unusual and looks like a battlefield where several plants compete for the same spot. Considering that the site is very probably checked by the Department of Conservation and mature plants often removed (Zero Density Control) that gives fair chances of survival and regeneration to most of the species present here. Old settled habitats look different plants share the habitat in a certain way depending on their ability to colonize or survive in certain circumstances, there is a naturally grouping that occurs and plants of the same vegetation layer dont mix readily. In some places one species eventually takes control and becomes the dominant form of vegetation, but not here! Of course, some of the species already mentioned are more abundant, some more isolated, but the amazing thing is that on only couple of square meters you can see here 4

27. Aloe arborescens growing directly on the lava blocks, next to Sedum praealtum ssp. praealtum and with the pohutukawa (Metrosideros excelsa) bush in the background.

28. This picture would be an ideal subject for a quiz like count the succulents; unfortunately I wouldnt be able to provide the right answer. Again, in the background the pohutukawa bush. Beyond this, there are totally different vegetation patterns with no succulent plants at all.


5 6 different species grow together and form a kind of vegetal mosaic, in a mix you usually dont see in the wild.

To visit the succulent site south of Yankee Wharf is worth the effort and is quite instructive too this is how our old fashioned garden succulents actually live in the wild, but youve got to be quick! The Department of Conservation might take its role very seriously when you expect the least.

XVIII. A new Aeonium natural hybrid in New Zealand? (Notes on Aeonium Rangitoto - I) (3)

Well, I honestly dont know the answer yet. I have briefly mentioned in previous accounts (E. Zimer, 2008 and 2009a) and also published few pictures of a very interesting natural Aeonium haworthii hybrid from the butchered colony just south of the Islington Bay wharf (I trust you will recall the pictures). My gut feeling is that it is an Aeonium haworthii x Aeonium undulatum re-crossed with Aeonium haworthii. It is not quite Aeonium haworthii; it also isnt the hybrid Aeonium haworthii x Aeonium undulatum (4) which used to be very common in the area before the Department of Conservation took action. It also does not look exactly like other horticultural hybrids I have seen in past years.

Long story short luckily I have collected two clones before the colony was decimated and planted them in my rock garden. In both cultivated and wild state this hybrid seem to cry out its uniqueness at least thats how I see it, but I am far from being an Aeonium expert. I am using one clone for propagation purposes, the other one for study and observations. It is too early to have a clear idea of how distinct this hybrid may be (I havent even seen it flowering) and depending on this it will be (or not) a formal description at some stage. However, by mid-winter 2010 I will start to distribute this plant under the provisional name Aeonium Rangitoto.

In the meantime enjoy the pictures (some of them already published) I have gathered for this short note and I will be delighted to hear other opinions as well.

29. One of the presumed parents Aeonium haworthii, a form which looks pretty much alike the true species. This plant used to be fairly common in the Aeonium colony of Islington Bay, but not occurring in big numbers.


30 - 32. The bulk of the plants are made of Aeonium undulatum, several distinct forms (I used to name them rusty and green apple). One of these types is the other parent of the hybrid which Giuseppe Tavormina reckons is similar to Aeonium Ray Stephenson. Unfortunately I have visited Rangitoto only in high summer, when all Aeonium plats have reduced rosettes. Almost all plants I have seen here were single stemmed. Possibly I few weeks from now (it is still winter here) I will visit this site again to see the plants (or whats left of them) in full vegetation.

33. Aeonium haworthii x Aeonium undulatum in habitat it is a gorgeous plant even with reduced rosettes. All plants I have seen in Rangitoto were single stemmed. This plant, re-crossed with Aeonium haworthii, has generated the exquisite form I have named Aeonium Rangitoto.


34. Aeonium haworthii x Aeonium undulatum in cultivation. This clone adjusted very well to my rock garden conditions and even started branching after some time. A second clone which I kept for a while potted in my greenhouse rushed in a premature flowering and eventually died without offsetting.

35. Aeonium haworthii x Aeonium undulatum in cultivation. It is the same clone in mid-spring, only one month later! Detail of the backside of the leaves. You can also see that it is freely branching.


36. The inflorescence of Aeonium haworthii x Aeonium undulatum - the clone rushing into a premature flowering only few months after it has been collected from Rangitoto. It probably couldnt cope with the greenhouse or potting conditions.

37 38. Aeonium haworthii x Aeonium undulatum flower detail (left) and a detail of single flowers borne in the axils of the bracts (right).


39. Aeonium Rangitoto in habitat. I can recall seeing just very few specimens in the Islington Bay colony. It was always forming multi-branched individuals.

40. Aeonium Rangitoto (clone 1) in cultivation. By the time I have collected this plant it was a small single rosette, but it started to branch in few months. I have kept this clone for the first 8 months potted in the greenhouse and remarkably it has maintained its look from the wild even few more months after I have planted it outdoors. This clone originates from a cutting as I couldnt uproot the plant in Rangitoto without massively damaging the roots. As it was somewhat lagging in vegetation behind the clone 2 (perfectly extracted from its natural habitat) I have decided to use clone 1 for propagation purposes.


41. Aeonium Rangitoto (clone 2) in cultivation, 13 months after a single rosette was collected from the Islington bay colony. Being uprooted with minimal damages I have planted it directly in my rock garden and did have a good vegetative development indeed. It has lost quite quickly the typical look it had in the wild.

42. Aeonium Rangitoto (clone 1) - leaf detail in mid autumn. In strong light it becomes slightly glaucous; unfortunately the powder is easily washed away in heavy rain.


Additional References:

E. Zimer - The naturalized Aeonium of Rangitoto Island (Hauraki Gulf, New Zealand) (2008) originally published in the International Crassulaceae Network (ICN) website www.crassulaceae.net in English version and in early 2009 in Romanian translation in Cactusi.com www.cactusi.com and ACC Aztekium www.aztekium.ro websites;

E. Zimer - Aeonium of Rangitoto (2009), in CSSNZ Journal, Vol. 62, No. 2 May 2009;

E. Zimer - The succulent corner at Yankee Wharf, Rangitoto Island (2009), in CSSNZ Journal, Vol. 62, No. 4 November 2009 in print;

Further Readings:

Andrea Julian The vegetation pattern of Rangitoto (1992) unpublished PhD thesis;

Craig J. Miller & al. ARK2020: a Conservation Vision for Rangitoto and Motutapu Islands (Journal of The Royal Society of New Zealand, vol. 24, 1994);

S.H. Wotherspoon & J.A. Wotherspoon The Evolution and Execution of a Plan for Invasive Weed Eradication and Control, Rangitoto Island, Hauraki Gulf, New Zealand (2003).

My Notes:

(1) This is actually an extended version of the article written in August 2009 for the CSSNZ Journal and it also includes a much wider selection of habitat pictures.

(2) The flower colour variation blue / white of Agapanthus praecox ssp. orientalis is the result of a simple Mendelian inheritance pattern and therefore botanically speaking these are not different forms. Of course, by horticultural manipulation and selection the colour variation can be eliminated. However, the blue gene seems to be dominant as in nature (it is very widely naturalized here in New Zealand) and cultivation the white flowering plants are somewhat less numerous even in mixed populations; here, probably to be consistent with the uniqueness of this corner, the white flowering form has a much higher occurrence than the blue one.

(3) Submitted also as a stand alone note to Margrit Bischofberger of International Crassulaceae Network www.crassulaceae.net (and sent by her to Ray Stephenson and Giuseppe Tavormina) which also became few weeks later the core of a short note published with the same illustrations on the ACC Aztekium website (www.aztekium.co.nz) in Romanian translation and in English in CSSNZ Journal, Vol. 63, No. 1 (February 2010 in print).

(4) This is the hybrid Giuseppe Tavormina reckons it is very similar to Aeonium Ray Stephenson.

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All errors, omissions and misconceptions are mine.

Eduart Zimer, August 2009

http://eduart.page.tl/Home.htm


eduart zimer - (sdu) - adventive plants - part 7 (2009)

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