Auckland Botanic Gardens trial, 2012–2017 Emma Bodley1, Jeffery Jones and Jack Hobbs

Introduction light infection (in this case bacterial of the was measured across the Arthropodium is a of about spot) where flavonoids, the widest part of the plant. Each selection 10 species native to Madagascar, important group of plant pigments was given an overall rating based on New Caledonia, Australia and found in petals and foliage, such as habit, size, and flowering period, along . Arthropodium was anthocyanin, are produced by the with pest and disease observations traditionally placed in the lily family plant to minimise UV damage. This red at ABG by an internal evaluation (Liliaceae), but current treatments colouration also develops after frosts. panel. The overall rating (between 1 include it in the . = poor performer and 10 = excellent Methods performer) was used to determine the Arthropodium bifurcatum and This report details the results of a list of top performers. Cultivars that A. cirratum (rengarenga or native Arthropodium trial undertaken scored 8 or more are considered top New Zealand rock lily) are at Auckland Botanic Gardens (ABG) performers and are recommended New Zealand native herbaceous to identify the top performing cultivars for growing in Auckland based on the perennial commonly used for Auckland conditions. Evaluations results of this trial (summarised in in amenity horticulture and home focused on assessment of overall Table 1). gardens2. They thrive in shady places ornamental merit, severity of bacterial and perform well in dry soils such as leaf spot and snail/slug damage. The trial ran for five years and was under trees, and are often used in concluded after flowering in January The trial was planted in May 2012 mass plantings. They provide effective 2017. in a shady bed under Callistemon in groundcover, being evergreen and the ABG trial garden. Three plants Results requiring minimal maintenance. Sprays each were planted of most selections; In Table 1 we have noted accession of white are produced on however some had just one or two numbers (unique eight digit numbers spikes in late spring and summer. plants. An annual application of blood linked to the ABG plant database) and bone fertiliser was applied in next to some unnamed selections of autumn and mulch applied as required. A. cirratum so that we can differentiate Deadheading occurred after flowering them from each other. Collection and before seed set; spent information including the supplier were removed at the same time as of the specific plant used in the trial deadheading in mid-January. Slug and can be identified for those interested. snail bait was applied during spring All star performers are cultivars and summer from 2012 to 2015. In the commercially available. final year of this trial no slug and snail bait was applied. NPK fertiliser was applied in May 2015. Data collection commenced in July 2014 with weekly flowering records and quarterly assessments of pests and diseases. Pests and diseases assessed included mollusc (snail and slug) damage and bacterial leaf spot. An estimate of the percentage of the plant affected was recorded Fig. 1 Bacterial leaf spot on Arthropodium and averaged at the end of the trial. foliage. Photo: Jack Hobbs. display, flower colour and foliage colour was recorded once In the last few years bacterial leaf spot during a flowering period. Height and (Fig. 1) has become more obvious on width of each plant was measured rengarenga in Auckland. It develops and averaged. Height of the plant was a red colouration on the foliage, a measured from the base of the plant defence to protect the leaves after a to the highest part of the foliage. Width Fig. 2 Arthropodium ‘Parnell’. Photo: Jack Hobbs.

1 Auckland Botanic Gardens, 102 Hill Road, Manurewa 2105, Auckland, New Zealand; [email protected] 2 A third native species, Arthropodium candidum (the small renga lily) is a diminutive plant that is cultivated but not used for mass plantings in the same way as the much larger other two species. Because it is not comparable, A. candidum was excluded from the ABG trial.

2 New Zealand Garden Journal, 2017, Vol. 20(1) Table 1 Summary results of the 20 Arthropodium selections comprising habit, size, flowering period, significant pest and disease responses and overall plant performance rating. An upright inflorescence is when the flower spike is vertical and flowers are held above the foliage. Habit and size Pests and Overall Name (height by width in cm) Flowering Disease rating A. cirratum Sparse foliage. Bacterial leaf 20120456 45 × 32 Early to mid-Dec. spot. 4 A. cirratum 20120459 55 × 40 Early to mid-Dec. Very few flowers. Snail damage. 5 A. cirratum Wide glaucous foliage. Late Nov to mid-Dec. Upright 20120457 62 × 32 inflorescence. Relatively clean. 7 A. cirratum No glaucous colouring on foliage. Mid-Nov to mid-Dec. Upright 20120458 63 × 40 inflorescence. Clean. 7 A. bifurcatum ‘Parnell’ Wide leaf. Offshore island form. Late Nov to mid-Dec. Upright Bacterial leaf spot 8 (Fig. 2) 57 × 31 inflorescence. on older leaves. A. cirratum Wide leaf. Late Nov to mid-Dec. Upright 20120460 59 × 67 inflorescence. Relatively clean. 7 Wide leaf. Late Nov to mid-Dec. Masses of flowers Bacterial leaf spot A. ‘Elite’ 47 × 30 and upright inflorescence. on older leaves. 7 A. cirratum Collapsing/lax habit. Nov to mid-Dec. Masses of flowers on Had the worst 20120463 58 × 37 arching inflorescence. bacterial leaf spot. 5 Mid-Nov to late Nov. Sparse, pink flowers Had the worst A. ‘Pink Elite’ 49 × 34 on upright inflorescence. snail damage. 6 A. bifurcatum Late Nov to early Dec. Slight pink ‘Downtown’ Good groundcover. flowers, free flowering. Dense, upright Some bacterial 8 (Fig. 3) 63 × 37 inflorescence held just above foliage. leaf spot. Narrow leaf. Floppy/lax habit. A. cirratum Unattractive plant. Early Nov to mid-Nov. Sparse flowering. Clean. 6 ‘Te Puna’ 57 × 38 A. ‘White Spire’ Foliage doesn’t have glaucous Early Nov to mid-Nov. Flowers not held Lots of snail (Fig. blush. Slightly streaky foliage. 6 4) 65 × 34 above the foliage. damage. Glaucous blush and compact habit. A. cirratum Good foliage plant. Early Nov to mid-Nov. Only two Relatively clean 6 20080250 47 × 31 inflorescences per plant. foliage. Early Nov to early Dec. Some flowers on A. cirratum Offshore island form. Wide foliage. upright inflorescence but few flowers per Relatively clean 6 19920891 58 × 36 inflorescence. foliage. A. cirratum Narrow foliage. Unimpressive habit. Mid-Dec to early Jan. Very small flower 19920399 47 × 33 size. Snail damage. 5 A. ‘Te Ngaire’ Narrow foliage. (Fig. 5) 54 × 35 Early Nov to mid-Dec. Few flowers. Snail damage. 6 A. bifurcatum Wide, dense foliage, slight glaucous ‘White Knight’ blush. Good foliage plant. Late Oct to early Dec. Upright, lots of Relatively clean 8* (Fig. 6) 62 × 32 flowers on inflorescence. foliage. Medium width foliage, offshore Late Oct to early Dec. Upright Clean foliage A. bifurcatum island form. inflorescence with medium density of but some snail 7 ‘Matapouri Bay’ 71 × 76 flowers. damage. A. bifurcatum Variegated streak and floppy ‘Joy Splash’ foliage. Sparse habit. Early Nov to early Dec. Sparse flowers. Clean but some 7 (Fig. 7) 62 × 29 snail damage. Small compact offshore island form. A. ‘Little Splash’ Slight glaucous colouring on foliage. Early to mid-Dec. Few flowers. Clean foliage. 6 42 × 24 *NB: Arthropodium bifurcatum ‘White Knight’ rated 8 in this trial but has not always performed to this level over the many years it has been grown at ABG.

Fig. 3 Arthropodium ‘Downtown’ Fig. 4 Foliage of Arthropodium Fig. 5 Arthropodium ‘Te Ngaire’. Fig. 6 Arthropodium ‘White (syn. A. ‘Avalanche’). ‘White Spire’. Photo: Jack Hobbs. Knight’. Photo: Jack Hobbs. Photo: Jack Hobbs. Photo: Emma Bodley.

New Zealand Garden Journal, 2017, Vol. 20(1) 3 The largest cultivar was A. bifurcatum can easily be divided vegetatively and Some of the plants that scored less ‘Matapouri Bay’ and the smallest can be multiplied in this manner more than 8 may perform better in more was A. ‘Little Splash’. Selections with rapidly than most Arthropodium. We shade than they received in our trial. the longest flowering period were also recommend A. bifurcatum ‘White Old spent leaves can be removed A. bifurcatum ‘White Knight’ and Knight’, however we would like to and flower spikes deadheaded after A. bifurcatum ‘Matapouri Bay’. emphasise that A. bifurcatum ‘White flowering. Knight’ will only do well in specific Origins of cultivars locations such as dry shade. Arthropodium bifurcatum ‘Downtown’ In our trials we found that selections was collected by Jack Hobbs and of the recently described offshore Graeme Platt from traffic islands island species A. bifurcatum make in Quay Street, Auckland in about the most impressive plants for 1994. Terry Hatch of Joy Plants, amenity use. Typically these are Pukekohe, believes that the original taller and more vigorous than most plants in Quay Street were plants he mainland selections with an attractive supplied Nancy Steen and Auckland glaucous hue on the upper surface City Council that he raised from seed of their relatively thick and wide supplied to him by Suzi Bedford arching foliage. In most cases their (an amateur plant conservationist Fig. 7 Close up of Arthropodium ‘Joy Splash’ inflorescences are taller, more upright from St Heliers, Auckland), probably foliage. Photo: Jack Hobbs. and overall more impressive than originally collected by Geoff Baylis Arthropodium ‘Pink Elite’ was most those of many A. cirratum selections. from the Three Kings Islands in the susceptible to mollusc damage However, A. bifurcatum is a Northland 1950s. species that may have less cold and A. bifurcatum ‘Joy Splash’ and Arthropodium bifurcatum ‘Joy Splash’, tolerance than selections derived from A. ‘Little Splash’ were the least as the name suggests, was raised by A. cirratum. susceptible to mollusc damage Joy Plants. It arose as a variegated (Fig. 8). Arthropodium bifurcatum ‘Matapouri seedling collected near Matapouri A potential variable environmental Bay’ is the most widely commercially Bay more than 10 years ago (Terry factor in this trial was that not all light available offshore island selection and Lindsey Hatch, pers. comm.). (from the Poor Knights). A. ‘Little levels were equal for all cultivars. This Arthropodium ‘Pink Elite’ was Splash’ was the only significantly may have affected their susceptibility collected by Jack Hobbs from a small Arthropodium variety in this to pests and diseases, and flower planting in Quay Street, Auckland in trial that is commercially available. It production. December 1992. It was selected for would be suitable for a small home its pinkish flowers. Conclusions garden or courtyard. We noted that Cultivars of A. bifurcatum that A. bifurcatum ‘Joy Splash’ does not Arthropodium bifurcatum ‘Matapouri performed well at ABG included create an effective groundcover Bay’ was introduced into cultivation A. bifurcatum ‘Matapouri Bay’, compared to other Arthropodium probably in the late 1980s by Bay A. bifurcatum ‘Parnell’ and selections. Bloom Nurseries of Tauranga (Bay A. bifurcatum ‘Downtown’. Bloom Nursery catalogue, Autumn- Arthropodium are best planted in A. bifurcatum ‘Downtown’ has Winter 1990; Metcalf, 1993) and dry shade. Sun may enhance the been marketed erroneously as named by Malcolm Woolmore. It production of anthocyanins which A. ‘Avalanche’ by Naturally Native was collected originally from a plant causes red spots on damaged leaves. nursery. A. bifurcatum ‘Downtown’ growing on the Poor Knights and then cultivated at a private garden half way between Tutukaka and Matapouri Bay, Northland in 1980s (Guy Bowden and Malcolm Woolmore, pers. comm.). The selection is variable in form as it appears to be generally propagated by seed. Arthropodium bifurcatum ‘White Knight’ may be a selection made in the 1980s from plants growing on the same property as A. bifurcatum ‘Matapouri Bay’ and were originally collected from a mainland coastal cliff in Northland opposite the Poor Knights. This plant was named by Malcolm Woolmore (Guy Bowden and Malcolm Woolmore, pers. comm.).

Fig. 8 Average percentage of bacterial leaf spot (blue) and mollusc (snail and slug) damage (red) on each variety of Arthropodium from July 2014 to March 2016.

4 New Zealand Garden Journal, 2017, Vol. 20(1) Arthropodium bifurcatum ‘Parnell’ was ‘White Spire’ References originally collected from Parnell Rose originated in the Otari Native Botanic Eadie, F. (2010). Flower colour Gardens in the late 1980s by Jack Garden and Wilton’s Bush Reserve and climate – why cool is best. Hobbs and Graeme Platt, and grown (Commercial Horticulture, July 1990; Commercial Horticulture, August/ on at ABG as a parent block in 1991 Metcalf, 1993). It was selected by the September. Pp. 49–51. which supplied the commercial trade curator of the time (1962 to 1991), Heenan, P.B.; Mitchell, A.D.; with seed. the late R.H. Mole, a well-known de Lange, P.J. (2004). plantsman. Arthropodium bifurcatum Arthropodium cirratum ‘Te Puna’ is a (Asparagaceae), a new species selection made by Mark and Esmé Acknowledgements from northern New Zealand. Dean in the 1990s when they were We would like to thank Kerry New Zealand Journal of Botany owners of Naturally Native NZ Plants Gillbanks (2014–2015) and Sarah 42: 233–246. in Tauranga. The original selections Wood (2016–2017) for collecting Metcalf, L.J. (1993). The cultivation were made from plants growing in a phenology and other data during the of New Zealand plants. Godwit clump on the foreshore of Omokoroa. trials. Thank you also to Guy Bowden, Press Ltd, Auckland. 260 pp. Their selection was named after the Murray Dawson, Esmé Dean, Ian Raven, P.H.; Evert, R.F.; Eichhorn, nearby area of Te Puna. The plants Duncalf, Lindsey Hatch, Terry Hatch, S.E. (2005). Biology of Plants. were selected because they were and Malcolm Woolmore who provided W.H. Freeman and Company smaller and particularly attractive and information on the origins of the Publishers, 7th edition. healthy looking (Esmé Dean and Ian cultivars mentioned above. Duncalf, pers. comm.).

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