Ficus rubiginosa

Ficus rubiginosa, the rusty fig or Port Jackson fig (damun in the Dharug language), is a species of flowering plant native to eastern Australia in the genus Ficus. F. rubiginosa is a seedling that can grow on other plants or rocks (lithophyte). It matures to a tree of 30 m (100 feet) in height and a trunk with a yellow-brown, buttressed trunk. The leaves are oval and glossy green and measure from

4 to 19.3 cm (1+1/2–7+1/2 in) long and 1.25 to 13.2 cm (1/2–5+1/4 in) wide.

These fruits are small and round, with a yellowish color. They can be ripened and turned red at any point in the year. However, they peak in spring and summer. The fruit, which is similar to all figs in appearance, is a syconium. It’s an inverted inflorescence that has the flowers covering an internal cavity. F. rubiginosa can only be pollinated by the fig wasnt species Pleistodontes imperialis. This may include four cryptospecies. Another fourteen species of wasps live in the syconia, some of them causing galls and others parasitising the pollinator wasps. There are also at least two species nematodes. The fruit is eaten by many birds, including parrots, pigeons, and passerines. Ranging along the Australian east coast from Queensland to Bega in southern New South Wales (including the Port Jackson area, leading to its alternative name), F. rubiginosa grows in rainforest margins and rocky outcrops. It can be used in shade trees in parks and public areas. When potted, it is suitable for indoor use or bonsai.

Description

A spreading, densely-shading tree when mature, F. rubiginosa may reach 30 m (100 ft) or more in height, although it rarely exceeds 10 m (30 ft) in the Sydney region. The trunk is buttressed and can reach 1.5 m (4 ft 11 in) in diameter. The bark is yellow-brown. It can also grow as on other plants as a hemiepiphyte, or 1-5 m (3-16 ft) high lithophyte. Alternately arranged on the stems, the ovate (egg-shaped), obovate (reverse egg-shaped) or oval-shaped leaves are anywhere from 4-19.3 cm (1+5/8–7+5/8 in) long and 1.25-13.2 cm (1/2–5+1/4 in) wide, on 7-8.2 cm (2+3/4–3+1/4 in)-long petioles (stalks that join the leaves to stems). They are smooth or bear tiny rusty hairs. There are 16 to 62 pairs of lateral veins that run off the midvein at an angle of 41.5-84.0deg, while distinct basal veins run off the midvein at an angle of 18.5-78.9deg. As with all figs, the fruit (fig) is actually an inverted inflorescence (compound flower) known as a syconium, with tiny flowers arising from the fig’s inner surface into a hollow cavity. F. rubiginosa is monoecious–both male and female flowers are found on the same plant, and in fact in the same fruit, although they mature at different times. Often growing in pairs, the figs are yellow initially and measure 4-10 mm (1/8–3/8 in) across. Ripening to red in colour, they are tipped with a small nipple and on a 2-5 mm (1/8–1/4 in) stalk. Fruits ripen throughout the year, although more so in spring and summer. Some trees have ripe and unripe fruit at the same time.

It closely resembles its relative, the Moreton Bay fig (F. macrophylla). They are often confused because they have similar ranges in nature. It is easy to distinguish the F.rubiginosa by their smaller leaves and shorter fruit stalks. It is also confused with the small-leaved fig (F. obliqua), the syconia of which are smaller, measuring 4-12 mm long and 4-11 mm in diameter, compared with 7-17 mm long and 8-17 mm diameter for F. rubiginosa.

Cultivation

Ficus rubiginosa was first cultivated in the United Kingdom in 1789, where it is grown in glasshouses. It is commonly used as a large ornamental tree in eastern Australia, in the North Island of New Zealand, and also in Hawaii and California, where it is also listed as an invasive species in some areas. It is useful as a shade tree in public parks and on golf courses. Not as prodigious as other figs, F. rubiginosa is suited to slightly more confined areas, such as lining car parks or suburban streets. However, surface roots can be large and intrusive and the thin bark readily damaged when struck. Tolerant of acid or alkaline soils, it is hardy to US Hardiness Zones 10B and 11, reaching 10 m (35 ft) high in 30 years. Planting trees 8-12 m (30-40 ft) apart will eventually result in a continuous canopy. The trees are of great value in providing fruit for birds and mammals, though drop large quantities of fruit and leaves, leaving a mess underfoot.

William Guilfoyle described a variegated New South Wales fig that was “12-15 feet high” in 1911. It was F. rubiginosa variegata . A variegated form is in cultivation on Australia’s east coast, and in the United States. It is a chimera lacking in chlorophyll in the second layer of the leaf meristem. The leaves have an irregular central green patch along the midvein with irregular yellow and green elsewhere. Leaves that grow in winter generally have larger green patches than those that do in summer. The chimera is unstable, and branches of all-green growth appear sporadically.

Despite the relatively large size of the leaves, it is popular for bonsai work as it is highly forgiving to work with and hard to kill; the leaves reduce readily by leaf-pruning in early summer. It is the best tree to learn from, and one of the most popular native species in Australia. Its bark remains smooth, and does not attain a rugged, aged appearance. Known as “Little Ruby”, a narrow-leaved form with its origins somewhere north of Sydney is also seen in cultivation.

F. rubiginosa can also be used as a houseplant in brightly lit areas. However, a variegated version requires brighter lighting. It has gained the Royal Horticultural Society’s Award of Garden Merit. It is easily propagated by cuttings or aerial layering.

The wood’s light colour is soft and brittle. It is lightweight and can be used to make small boxes and toys.

Ecology

The fruit is consumed by many bird species including the rose-crowned fruit-dove (Ptilinopus regina), wompoo fruit-dove (P. magnificus), wonga pigeon (Leucosarcia melanoleuca), topknot pigeon (Lopholaimus antarcticus), Pacific koel (Eudynamys orientalis), Australasian swamphen (Porphyrio melanotus), Australian king parrot (Alisterus scapularis), Australasian figbird (Sphecotheres vieilloti), green catbird (Ailuroedus crassirostris), regent bowerbird (Sericulus chrysocephalus), satin bowerbird (Ptilonorhynchus violaceus) and pied currawong (Strepera graculina), as well as the mammalian grey-headed flying fox (Pteropus poliocephalus), and spectacled flying fox (Pteropus conspicillatus). It is one of several plant species used as food by the endangered Coxen’s fig parrot. Many fruits drop onto the ground around the tree, though others are dispersed by animals that eat them.

The Gynaikothrips Australis thrips species feeds on the undersides of new leaves of F. rubiginosa as well as F. obliqua, F. macrophylla. Nearby cells become meristem tissues and the plant cells that die are stimulated to form galls. The leaves then turn distorted and curl up. The thrips start feeding after the tree has produced new growth. They live for approximately six weeks. Other times, the thrips will live on old leaves and not feed. The bark shelters the species as it is home to its pupae. The thrips stay in the galls during the night and wander around the tree in the morning, returning to the galls in the evening. Psyllids have almost defoliated trees in the Royal Botanic Gardens in Sydney in spring.

P. imperialis crossed the waters between Australia and New Zealand some time between 1960 and 1972, and seedlings of the previously infertile trees of F. rubiginosa began appearing in brick and stone walls, and on other trees, particularly in parks and gardens around Auckland. They have been recorded as far south as Napier. P. imperialis has been transported to Hawaii, California and Israel, where it has been observed to pollinate its host.

They can live up to 100 years and are known to reseed after bushfires, producing fruit in three years.

Other life in the syconia

As with many other Ficus species, the community of wasps inside the figs of F. rubiginosa is made up mostly of pollinator wasps. These develop deep inside the syconium, presumably protected there from parasites. Also present are much smaller numbers of other wasp species, which do not pollinate the fig. At least fourteen species have been recorded, of which four–two each belonging to the genera Sycoscapter and Philotrypesis–are common while others are rare. Investigation of F. rubiginosa syconia found that the fig seeds and parasitic wasps develop closer to the wall of the syconium. The wasps from the genera Sycoscapter, Philotrypesis have a parasitic nature and are approximately the same size as pollinator species. Their larvae are thought to feed on the larvae of the pollinator wasp. Male Sycoscapter and Philotrypesis wasps fight other males of the same species when they encounter each other in a F. rubiginosa fig. Several genera of uncommon larger wasp species enter the immature figs before other wasps and induce galls, which may impact on numbers of pollinator wasps in the fig later. An example of this is Pseudidarnes minerva, a metallic green wasp species.

The genus Schistonchus has nematodes that can be found in the syconias (and pollinator wasps), of many species figs, with F. Rubiginosa hosting two. They seem to be less species-specific that wasps. S. altermacrophylla is generally associated with F. rubiginosa though it has been recorded on several other fig species.

Taxonomy

Ficus rubiginosa was described by French botanist René Louiche Desfontaines in 1804, from a type specimen whose locality is documented simply as “New Holland”. In searching for the type specimen, Australian botanist Dale Dixon found one from the herbarium of Desfontaines at Florence Herbarium and one from the herbarium of Étienne Pierre Ventenat at Geneva. As Ventenat had used Desfontaines’ name, Dixon selected the Florence specimen to be the type in 2001. The specific epithet rubiginosa related to the rusty coloration of the undersides of the leaves. Indeed, rusty fig is an alternate common name; others include Illawarra fig and Port Jackson fig. It was known as damun (pron. “tam-mun”) to the Eora and Darug inhabitants of the Sydney basin.

In 1806, German botanist Carl Ludwig Willdenow gave it the botanical name Ficus australis in Species Plantarum, but this is a nomen illegitimum as the species already had a validly published name. Italian botanist Guglielmo Gasparrini broke up the genus Ficus in 1844, placing the species in the genus Urostigma as U. rubiginosum. In 1862, Dutch botanist Friedrich Anton Wilhelm Miquel described Urostigma leichhardtii from material collected from Cape Cleveland, Queensland, noting it had affinities to F. rubiginosa. In 1867, he placed Urostigma as a subgenus in the reunited Ficus, which resulted in the taxon becoming Ficus leichhardtii. Miquel also described Ficus leichhardtii variety angustata from Whitsunday Island, later classified as F. shirleyana by Czech botanist Karel Domin. Queensland state botanist Frederick Manson Bailey described Ficus macrophylla variety pubescens in 1911 from Queensland, Domin later renaming it Ficus baileyana. All these taxa were found to be indistinguishable from (and hence reclassified as) F. rubiginosa by Dixon in 2001.

In a study published in 2008, Nina Rønsted and colleagues analysed the DNA sequences from the nuclear ribosomal internal and external transcribed spacers, and the glyceraldehyde-3-phosphate dehydrogenase region, in the first molecular analysis of the section Malvanthera. They found F. rubiginosa to be most closely related to the rainforest species F. watkinsiana and two rock-growing (lithophytic) species of arid northern Australia (F. atricha and F. brachypoda). They classified these species in a new series Rubiginosae in the subsection Platypodeae. Relationships are unclear and it is uncertain into which direction the group radiated (into rainforest or into arid Australia).

Joseph Maiden described variety lucida in 1902, and Bailey described variety glabrescens in 1913. Both had diagnosed their varieties on the basis of their hairlessness. Maiden described a taxon totally devoid of hair, while Bailey described his as nearly glabrous (hairless). As Bailey’s description more closely matched Dixon’s findings (that these variants were only partly and not completely hairless), Dixon retained Bailey’s name and reclassified it as Ficus rubiginosa forma glabrescens in 2001 as it differed only in the lack of hairs on new growth from the nominate form.