Chilean mayten ( boaria) – a ticking time-bomb? Murray Dawson1

Experts reckon that about 20 new ‘jump the garden fence’ each year to become naturalised in New Zealand (Ewen Cameron, Auckland Museum, pers. comm.). One such that I, and others, have become increasingly concerned about – particularly around my home area of Canterbury – is (also called Chilean mayten, mayten or maiten). Unfortunately, this species now appears to be a ticking time-bomb and has real potential for explosive spread to become a major environmental weed throughout New Zealand. This article describes what Chilean mayten is, its history of introduction, Fig. 1 Habit of 30-year old tree growing in the Fig. 2 Trunk showing fissured grey bark why it’s become a problem, and what CASC grounds, Lincoln. This female tree is (same tree as Fig. 1). we can do about it. the source that has caused its spread on Photo: Murray Dawson. that campus. It has now been cut down and What is Chilean mayten? the stump poisoned. Photo: Murray Dawson. There are more than 50 species of Maytenus and most are tropical. Several are said to have been cultivated in New Zealand2, but M. boaria is by far the most widely grown due to its cold-tolerance and horticultural qualities. Chilean mayten belongs to the family and is native to , naturally occurring from about 30 to 50ºS in and . This evergreen tree is fairly hardy and drought resistant. It’s cultivated as a small to medium sized tree, typically reaching 6–8 m after several decades (Fig. 1). However, under optimum conditions and given enough time it can eventually grow up to 20–30 m tall. It has fissured grey bark (Fig. 2). When mature, this graceful tree develops a straight trunk and pendulous branchlets that sway in the Fig. 3 Characteristic serrated foliage and small . Female shrub. Photo: Murray Dawson. wind, similar in effect to a weeping willow (Salix babylonica) or the Western Australian peppermint tree (Agonis flexuosa).

1 Landcare Research, PO Box 69040, Lincoln 7640, New Zealand; [email protected] 2 (Lam.) Hook.f. and M. vitis-idaea Griseb. (endemic to South America), M. canariensis (Loes.) G.Kunkel & Sunding (endemic to Spain), M. silvestris Lander & L.A.S.Johnson (endemic to Australia), and M. vitiensis (A.Gray) Ding Hou (of the South Pacific).

28 New Zealand Garden Journal, 2016, Vol. 19(2) Chilean mayten are alternately arranged, glabrous (hairless), glossy and dark green on the upper surfaces, lighter green on the lower surfaces, and shortly petiolate (with -stalks 1.3– 6 mm long). The leaves are relatively small ((15–)20–60(–75) mm long), narrowly lanceolate to elliptic, and with finely serrated margins (Fig. 3). In New Zealand it flowers from late August to early October. Its flowers are solitary or arranged in axillary clusters (arising from the stems), small (about 5 mm in diameter), 5-merous, greenish- A yellow and relatively inconspicuous. A There are separate male (Fig. 4A–B) and female (Fig. 5A–B) plants – they are either all-male or all-female (i.e., the species is dioecious and you don’t get male and female flowers together on the same plant).

B Fig. 7 Old capsules persisting on tree after the fruit has been dispersed. A, general view. B B, close-up view. Photos: Murray Dawson. Fig. 5 Female flowers. A, flowers showing stigmas and superior ovaries. B, close-up Early garden records side view of . Photos: Murray Dawson. Searching the outstanding Papers Past resource (https://paperspast.natlib. govt.nz), the earliest record that I found of Maytenus being introduced into New Zealand is 1881, where “Maytenus pendulinus, the South American spindle A tree” is noted as a new arrival, as part of the Christchurch Domain Board’s plant exchange programme (Some New Arrivals, The Star, Issue 4161, A August 22, 1881, p. 3). Maytenus pendulina Steud. is probably a synonym for the currently accepted name Maytenus boaria Molina. It is apparent that mayten successfully established from early imports such as this, as a large specimen of “Maytenus chilensis” was highlighted as growing in the Christchurch Botanic B Gardens in a 1945 guide (Visitors’ Fig. 6 Mature fruit. A, fruit showing orange- Guide to Christchurch, The Press, red arils. B, close-up view. Vol. LXXXI, Issue 24594, June 16, Photos: Peter Heenan, 1945, p. 6). Maytenus chilensis DC. © Landcare Research 2015. B is a valid synonym for Maytenus Seed formed on female plants boaria. In 1962, Bill Sykes collected a Fig. 4 Male flowers. A, flowers showing mature from March to June, and are herbarium specimen (Allan Herbarium, yellow anthers. B, close-up side view of surrounded by orange to dark red CHR 130131) from a tree he estimated flower. Photos: Murray Dawson. coloured fleshy arils (Fig. 6A–B). The to be a remarkable 100 ft (30 m) tall, persistent fruit capsules are yellowish- cultivated in the gardens. In the same brown in colour (Fig. 7A–B). year, 1962, Diane Smith also lodged

New Zealand Garden Journal, 2016, Vol. 19(2) 29 a specimen collected in the gardens of the original root zone3. For Chilean (Christchurch Botanic Gardens mayten, seedling spread is a more Herbarium, CHBG 1738). robust determiner of naturalisation and I would not consider 1975 as the year of In 1929, “Maytenus escallonicus” naturalisation here. became commercially available in New Zealand, and was listed as a 1986 specimens from Hunters Gully new shrub in a Duncan & Davies above Church Bay (CHR 437248, nursery catalogue of that year. This collected by Bill Sykes, and species name does not appear to be CHR 497744, collected by Hugh valid. However, in a later Duncan & Wilson) may represent the earliest likely Davies catalogue (c. 1947) the name record of naturalisation from seedlings. “Maytenus chilensis” is instead used, However, unless you pull the emergent and that catalogue description is a shoots out of the ground, it’s difficult good match for Chilean mayten: “E to confirm what material they are [evergreen]. In maturity the slender arising from. Central root leaders are branches develop a weeping habit, characteristic of seedlings, and suckers which in combination with the small arise from mature tree roots growing bright green leaves makes this a very horizontally near the surface. The attractive tree. 12 ft.” aforementioned herbarium specimens from Church Bay don’t show any below Eastwoodhill Arboretum’s stock records ground parts. (unpub. data) show that their first Fig. 8 Herbarium specimen (CHR 621564) collected by C.C. Ogle from Bason Botanic accessions of this tree date from 1935, In the Gisborne and Whanganui Gardens showing obvious seedlings. from Stevens Brothers Nursery in Bulls, regions, there is additional evidence Photo: © Landcare Research 2017. New Zealand. Eastwoodhill’s 1948 from herbarium collections of Chilean So why is Chilean mayten now imports came from Hillier Nurseries in mayten escaping from cultivation. becoming invasive more than 130 Winchester, UK. In 1989, Bill Sykes collected specimens years after its first introduction into Chilean mayten as a weed (CHR 463199A–C and CHR 463200A– New Zealand? Why is this previously Webb (1988) recorded Chilean C) from trees growing nearby but benign tree going rogue? mayten as naturalised in the Flora of outside of the boundary of Eastwoodhill Full credit goes to Joe Cartman, New Zealand, Vol. 4. He mentioned two Arboretum. Bill returned in later years Christchurch City Council Nursery collections from Canterbury – one from to collect female specimens cultivated Supervisor and a renowned plantsman, a footpath and gutter in Christchurch within the arboretum (CHR 472607, for unlocking this puzzle. He realised and the other from a single thicket collected 1991, and CHR 497192A–D, that up until the mid-1980s only male growing amongst indigenous trees at collected 1994). A management goal plants were sold by nurseries. This Church Bay, Banks Peninsula. of Eastwoodhill is to remove Chilean was based on observations he made mayten from the park which involves I have examined these and other of dozens of trees around Christchurch cutting down the tree, removing all Allan Herbarium (CHR) specimens of and elsewhere, all males and probably suckers and poisoning the stumps. Chilean mayten and the accompanying a tendency applicable to the rest of Full control is difficult to achieve given collectors’ notes. New Zealand at that time. Cartman their current resources (Dan Haliday, commented that these male plants The late A.J. Healy (a weed expert from pers. comm.). Suckers are more easily appeared to be uniform and probably the then Botany Division, DSIR) noted controlled if stock are on-site to eat from the same clone. Material would in his 1975 collection from Clyde Road, them, or if the tree has been planted as be easy to propagate vegetatively by Christchurch (CHR 326322; referred a lawn specimen so any suckers are pulling up suckering shoots (Fig. 9) and to by Webb 1988) that his specimens constantly mown down. growing them on through root cuttings. were taken outside of a residential More recently, in 2012, Colin Ogle section where planted trees were Unfortunately, this status quo changed. collected for the Allan Herbarium suckering out through the footpath and Cartman and McCombs (2002) noted obvious Chilean mayten seedlings gutter channel. that from the mid-1980s seed-grown complete with roots – these came from plants started to appear on the market, In some growing conditions, these Bason Botanic Gardens, Westmere, and inevitably some of these were suckers can form dense thickets more near Whanganui (CHR 621564; Fig. 8). female. Birds love to eat the fleshy than 10 m away from the parent tree. Colin tells me that he has alerted the seed-containing arils and thus Chilean I’m not certain that suckering from a Friends of Bason Botanic Gardens mayten has literally now gained wings cultivated tree (even after it is cut down) about the emerging threat that Chilean in New Zealand. This has allowed represents a genuine naturalisation mayten presents. Hopefully, they will the species to disperse well beyond event in all cases, as material may not set about to remove at least the female the original (all-male) plantings and to spread far beyond the confines trees from their gardens. colonise new areas.

3 Conversely, for some species such as bamboos naturalised in New Zealand, soil excavation and transport to new sites can indeed lead to new wild plants.

30 New Zealand Garden Journal, 2016, Vol. 19(2) (pers. comm.) has seen plants treatments, spraying with Starane® appearing in parts of the amenity area (60 ml per 10 litres) to be the most where it was never planted, suggesting effective, killing off all adult trees along that it may also be spreading on that with their suckers that were growing campus by seed dispersal. up to 6 m away from the parent trees (some, but not all, of those suckers were sprayed along with the parent foliage). Drilling and filling trunks with Tordon® was the next most effective treatment, and Roundup® on its own was less effective4. Starane® spray also effectively killed off Chilean mayten seedlings. Based on NatureWatch NZ ‘Citizen Fig. 9 Suckering from a tree that was cut Science’ observations, Central down more than 15 years ago at the CASC Canterbury appears to be a primary grounds, Lincoln. Photo: Murray Dawson. source of spread in New Zealand Cartman and McCombs (2002) (Fig. 11). Several recent observations recounted that around 1990, several of include: the seed grown plants were purchased • Suckers coming up in a garden and planted out in a shelterbelt at the more than ten years after the adult Christchurch City Council nursery in tree was killed by Jon Sullivan and Gardeners Road, Harewood (e.g., Fig. 10 Suckers (shown in the foreground) the stump and all suckers being CHR 478917, collected from the from a large mature tree (background) liberally treated with Vigilant® nursery by Bill Sykes in 1988). Within cultivated at Lincoln University, Canterbury. herbicide gel (http://naturewatch. Photo: Murray Dawson. a few years of planting, Joe Cartman org.nz/observations/3659022). observed numerous seedlings John Stevens told me of his personal • An observation by Jon Sullivan of emerging in the vicinity of the original horror story of Chilean mayten infesting a wild sapling found in the middle tree (e.g., CHR 567754A–B, collected his native plantings at Willowbridge, of Bottle Lake Plantation growing by Peter Heenan in 2003). They cut near Waimate, and his efforts to under tall pines (http://naturewatch. down this tree but found the seedlings control it. From 2001, John planted org.nz/observations/2537947). and suckers persistent and difficult more than 10,000 native plants on to control. They repeatedly poisoned 4 ha of his land. This revegetated area • A mature female tree with the stump and removed regrowth. Joe gained a QEII covenant in May 2007. numerous seedlings or suckers Cartman (pers. comm.) tells me that Unfortunately, around 2002–2003 his in Kaiapoi (http://naturewatch.org. Roundup® kills the seedlings (using neighbour on the opposite side of the nz/observations/1000227), and a ×1.5 dose rate and with penetrant road planted a shelterbelt that included observations by Sue McGaw in added). some 50 plants of Chilean mayten, many other locations on earthquake recommended for that purpose by a abandoned wasteland in Kaiapoi. It’s a similar story at my workplace local plant nursery. Obviously, some of campus, the Canterbury Agriculture Chilean mayten is a master of disguise those trees must have been females as and Science Centre (CASC) at Lincoln, and hides amongst native shrubs, so 13–14 years after the shelterbelt was Canterbury. Landscaping planted it may well have been overlooked in planted, thousands of Chilean mayten in the early 1990s by the former other regions. When it’s still a shrub, seedlings became apparent in John’s Ministry of Works included a female it looks rather nondescript with its native plantings across the road. These Chilean mayten tree in the South small evergreen leaves and (unless appeared as isolated plants and also American courtyard garden (Fig. 1–2). in fruit) few distinguishing features. thick patches of seedlings (particularly Fast forward to the present, and Chilean mayten looks a lot like a native under native trees and shrubs favoured sure enough, saplings are rampant New Zealand plant, and resembles by the birds to roost on). John’s throughout our native and exotic a small leaved maˉhoe (Melicytus) neighbour readily agreed to kill the plantings on campus, some male and or perhaps a ribbonwood (Hoheria). Chilean mayten from the shelterbelt, others female. Worse, it’s very shade tolerant so and together they trialled different can co-exist with and then potentially At the nearby Lincoln University treatments in 2016. These trials outcompete in native ecosystems, campus, suckers are persisting from included spraying the foliage of the 4 m restoration areas, and amenity trees that were originally planted there tall trees with Starane® herbicide, and plantings. but have been cut down, and fully drilling and filling holes in the trunks mature trees that are still cultivated and with neat Roundup®, Tordon® and a As a result of its weedy characteristics, also suckering (Fig. 10). Roy Edwards 50:50 mix of the two. They found of all Chilean mayten was added to the

4 Cartman and McCombs (2002) also tried drilling and filling with Roundup®. They note that “Plants have been drilled and the holes filled with 60% Roundup solution. This kills about half the treated stems. In comparison, this method has a 100% kill of hawthorn, spindleberry, sycamore and eucalypts elsewhere within the shelterbelt. Poisoning is necessary as merely cutting the plants stimulates a mass of root suckers.”

New Zealand Garden Journal, 2016, Vol. 19(2) 31 Acknowledgments I thank Joe Cartman, John Clemens, Roy Edwards, Dan Haliday, Sue McGaw, Colin Ogle, John Stevens and Jon Sullivan for helpful comments on drafting this article, and Peter Heenan for permission to use his excellent fruit images (Fig. 6). My images used in this article have also been added to the NatureWatch NZ platform. References Cartman, J. and McCombs, K. (2002). Fig. 11 Distribution of Maytenus boaria in Central Canterbury. Map generated from Maytenus boaria – a new weed? NatureWatch NZ (http://naturewatch.org.nz). (Available at https://web.archive. org/web/20050108160137/ National Pest Plant Accord (NPPA) in removing the resulting suckers and a http://www.ccc.govt.nz/ 2012, banning its sale, distribution and legacy of seedlings. parks/TheEnvironment/ propagation in New Zealand. Summary MaytenusBoariaCCCECO0206. It was with some surprise then that I A timeline of known information for asp). spotted mayten listed in a landscaping Chilean mayten establishment in Duncan & Davies (1929). General and tree planting appendix to New Zealand is: Catalogue of Choice Nursery the proposed 2014 Christchurch Stock, p. v. (Available at • 1881: Introduced into the Replacement District Plan. Needless www.rnzih.org.nz/pages/ Christchurch Botanic Gardens from nurserycatalogues.html). to say, because of its NPPA status, I overseas. tendered a written submission pointing Duncan & Davies (undated, out that it cannot now be considered • 1929: Sold commercially by Duncan c. 1947). Catalogue of Choice Nursery Stock, p. 44. (Available for planting under any circumstances. & Davies nursery, New Plymouth. at www.rnzih.org.nz/pages/ This is somewhat ironic as Joe Cartman • Mid-1980s: Seed-grown plants nurserycatalogues.html). and Kate McCombs, who raised the started to be sold, including females. Salmon, J.T. (1999). The trees in alarm in the first place, are (and were • 1986/1989: Recorded as naturalised New Zealand. Exotic trees: respectively) Christchurch City Council from herbarium specimens. the broadleaves. Reed Books, employees. Also, their informative Auckland. 2002 article no longer appears to • 2002: Joe Cartman and Kate Webb, C.J.; Sykes, W.R.; Garnock- be retrievable directly from the CCC McCombs published an article Jones, P.J. (1988). Flora of outlining the emerging weed threat. website. New Zealand, Volume IV. Maybe Environment Canterbury and • 2012: Chilean mayten was added to Naturalised pteridophytes, other regional authorities can step up the NPPA list. gymnosperms, dicotyledons. and include Chilean mayten in their next • Present day: Citizen Science Botany Division DSIR, Christchurch. Regional Pest Management Strategy? observations indicate the expanding I think that there is a strong case for distribution of this species, Websites (accessed December doing so. particularly in Canterbury. 2016) Flora of New Zealand: Maytenus What can you or I do about this Weedy characteristics of Chilean boaria Molina: www.nzflora.info/ ticking time-bomb? I repeat Cartman mayten include: factsheet/Taxon/Maytenus-boaria. and McCombs (2002) plea for early • Long-lived. html intervention, now made nearly 15 years • Drought resistant. NatureWatch NZ: Maiten tree ago. We need sharp eyes looking out (Maytenus boaria): http:// for this new pest plant. Saplings and • Persistent suckering from roots. naturewatch.org.nz/taxa/77969- trees – of females in particular – should • Resistant to poisoning. Maytenus-boaria be hunted down and actively removed • Very shade tolerant but also grows New Zealand Plant Conservation as soon as possible to prevent further in full sun. Network: Maytenus boaria: spread of seedlings. The cost of inaction • Difficult to distinguish from www.nzpcn.org.nz/flora_details. could well be a new environmental New Zealand native plants. aspx?ID=3460 weed becoming established throughout • Flowers and from an early age Papers Past (digitised historic New Zealand, and perhaps capable of New Zealand newspapers): (3–5 years, 2 m tall). invading native forest. Let’s hope that https://paperspast.natlib.govt.nz/ it’s not already too late. • Seed readily dispersed by birds. newspapers/19450616.2.45?quer I’ve ‘walked-the-talk’ and had the adult y=Maytenus tree (Fig. 1) and a female sapling on my : Angiosperms – campus cut down. No doubt we will be Celastraceae – Maytenus: spending several frustrating decades www.theplantlist.org/1.1/browse/A/ Celastraceae/Maytenus/

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