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Common name:     Buckthorns                 

Etymology of scientific name:   From Ancient Greek ῥάμνος rhámnos referring to various prickly shrubs, such as boxthorn

Flowers:                  

• The flowers are radially symmetrical. There are 5 (sometimes 4) separate sepals and 5 (sometimes 4 or none) separate petals. The petals may be white, yellowish, greenish, pink or blue, and are small and inconspicuous in most genera, though in some (e.g. Ceanothus) the dense clusters of flowers are conspicuous. The 5 or 4 stamens are opposite the petals.[2] The ovary is mostly superior, with 2 or 3 ovules (or one by abortion).

Fruit:                         

• The fruits are mostly berries, fleshy drupes, or nuts. Some are adapted to wind carriage, but most are dispersed by mammals and birds. Chinese jujube is the fruit of the jujube tree (Ziziphus zizyphus) and is a major fruit in China.

Leaves:         

•  Leaves of family Rhamnaceae members are simple, i.e., the leaf blades are not divided into smaller leaflets.[2] Leaves can be either alternate or opposite. Stipules are present. These leaves are modified into spines in many genera, in some (e.g. Paliurus spina-christi and Colletia cruciata) spectacularly so. Colletia stands out by having two axillary buds instead of one, one developing into a thorn, the other one into a shoot.   

Habit:        

• Rhamnaceae is a large family of flowering plants, mostly trees, shrubs, and some vines, commonly called the buckthorn family

Habitat:                       

• Worldwide distribution, but are more common in the subtropical and tropical regions. The earliest fossil evidence of Rhamnaceae is from the Late Cretaceous. Fossil flowers have been collected from the Upper Cretaceous of Mexico and the Paleocene of Argentina.

Species:                     

• World:            950 S,    55 G

• Australia:      S,    G

Additional notes:                 

• Economic uses of the Rhamnaceae are chiefly as ornamental plants and as the source of many brilliant green and yellow dyes

• The wood of Rhamnus was also the most favoured species to make charcoal for use in gunpowder before the development of modern propellants                       

• Etymology

  • From the type genus Rhamnus, Latin rhamnus meaning a thorn bush, thorny shrubs

• Common Name: Buckthorn family

• Description

  • Shrubs, trees or lianes (rarely herbs outside Australia), perennial, usually with simple, bifid or stellate, non-glandular hairs at least on young growth

  • Leaves simple, alternate (rarely opposite), usually symmetric (oblique in Ziziphus); stipules present or sometimes almost lacking, sometimes spiny

  • Inflorescences terminal or axillary, bracteate, cymose but sometimes appearing racemiform or paniculate or reduced to dense heads, few-flowered clusters or single flowers. Flowers small, usually bisexual and protandrous, actinomorphic, 4- or 5-merous. Hypanthium funnel-shaped to shallowly dish-shaped, sometimes extended into a distinct tube. Sepals valvate, usually adaxially keeled. Petals usually clawed, often small and hood-like, sometimes absent. Stamens isomerous with the sepals, opposite the petals and often enclosed by them; anthers 2-locular, dorsifixed, introrse, longitudinally dehiscent. Disc usually conspicuous, filling or lining the hypanthium or forming a ring around the summit of the ovary or a shelf at the apex of the hypanthium. Ovary at anthesis half- to fully-inferior (sunk in the disc), rarely superior; carpels 2–5; ovule one per loculus, erect; style almost entire to deeply divided. Fruit a capsule, schizocarp, drupe or samara. Seeds usually arillate with a large embryo and scanty endosperm.

• Diagnostic Features

  • The small flowers with stamens adjacent to the petals and often cupped within them is characteristic

  • Many Australian species are stellate-hairy on young stems and leaf undersurfaces

• Distribution

  • An almost cosmopolitan family of 50–60 genera and c. 900 species, most diverse in the tropics and warm dry regions, particularly in Central America and Asia; 25 genera and c. 260 species occur in Australia

  • Australian Rhamnaceae can be divided into two principal groups, one of 9 mainly northern genera each with relatively few species often with relatives beyond Australia in Malesia and Asia, the other of 10 endemic or near-endemic, species-rich, principally southern-temperate genera

  • Four species in four genera are naturalised, while a few others are cultivated as ornamental or fruit trees.

• Habitat

• The large southern-temperate genera are most commonly found in heathlands, shrublands and woodlands; the tropical genera are often found on rainforest edges

• Few species occur in arid biomes

• Uses

  • There are many uses of the fruit of Ziziphus zizyphus, a species probably originating in southern Asia, and now extensively cultivated for food (fresh, dried, pickled, candied, smoked, jams, paste, syrup, teas, juice, vinegar, alcohol, used in deserts and beverages) and medicines (e.g. used in traditional Chinese medicine)

  • Ceanothus (Californian Lilacs) from America includes many showy species (including hybrids and cultivars) grown as ornamentals; also several other genera are cultivated as ornaments 

  • Green and yellow dyes are derived from the berries or bark of several Rhamnus species (see Jury 2007)

  • Some taxa are used for timber.

• Notes

  • The degree of fusion of the ovary with the hypanthium, both in flower and fruit, is important in identifying genera of Rhamnaceae

  • Many genera (e.g. Cryptandra, Trymalium) have ovaries that are inferior (or sunken in the disk) at anthesis

  • After anthesis the roof of the ovary (that part which lies inside the hypanthium around the style base and inside or below the disk) bulges upwards so that in the mature fruit the ovary appears half-inferior or sometimes almost fully superior

  • In other genera (e.g. Spyridium, Stenanthemum) the ovary roof remains flat during maturation of the fruit, and hence the ovary remains inferior

  • The disc and/or perianth may persist on the mature fruit, or remain as a thickened rim or scar

  • In the descriptions these remnants are called the torus of the fruit

  • In genera in which the ovary roof does not bulge after anthesis the torus will usually lie around the fruit apex, while in those with a bulging roof, it will encircle the fruit around the middle or towards the base

• Source: Atlas of Living Australia

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