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Article from Bean's Trees and Shrubs Hardy in the British Isles
Article from New Trees by John Grimshaw & Ross Bayton
'Olea europaea' from the website Trees and Shrubs Online (treesandshrubsonline.
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An evergreen tree of rugged, much-branched habit and slow growth, generally 15 to 30 ft high, with grey-green foliage. Leaves opposite, narrowly obovate or oval, 11⁄2 to 3 in. long, 1⁄3 to 3⁄4 in. wide, glaucous or silvery beneath, leathery. Flowers white, 1⁄5 in. diameter, in axillary racemes 1 to 2 in. long, the corolla with four ovate lobes; stamens two. Fruit an oval, oily drupe, 3⁄4 in. long, containing a bony seed.
Probably with an origin in S.W. Asia and largely cultivated all over the Mediterranean region. In many parts of Italy, as in the environs of Florence, its grey tints give the prevailing tone to the landscape. In Britain it can only be cultivated out-of-doors in the mildest parts. It has borne fruit in several places in the south-west. At Kew it has lived for a good many years on a south wall, but in such a place is only worth growing for its interest and associations. In the Chelsea Physic Garden, London, there is an example in the open ground, on three stems and about 20 ft high. It was bearing a few almost ripe fruits in January 1975.
The European Olive (see Bean and Krüssmann: B25, K331) has long been known in cultivation, with a history that needs no elaboration here. The taxon that occurs most commonly is Olea europaea subsp. europaea, with var. europaea being the cultivated Domestic Olive, and var. sylvestris (Mill.) Lehr (formerly var. oleaster (Hoffm. & Link) DC.) the wild, Mediterranean Olive (K331). Numerous cultivars have been selected, whether for fruit or solely for their ornamental qualities, and these should be chosen in preference to the unspecified plants sold as tiny saplings with a bottle of olive oil strung round their necks, or as pillaged veterans of ancient groves.
In total, six subspecies of O. europaea are recognised, of which subsp. cuspidata is described below. They are largely distinguished by leaf size and distribution. Subsp. cerasiformis G. Kunkel & Sunding of Madeira and subsp. guanchica P. Vargas et al. of the Canary Islands have linear to narrowly elliptic leaves, (3–)4–6(–8) × (0.3–)0.4–0.6(–0.8) cm. Subsp. laperrinei (Batt. & Trab.) Cif. of the Sahara and subsp. maroccana (Greuter & Burdet) P. Vargas et al. of Morocco have narrowly elliptic leaves, (3–)4–5(–7) × (0.5–)0.6–1(–1.5) cm (Green 2002). These would probably all be worth trying in favourable sunny sites, if material were to become available.
O. africana Mill.
O. chrysophylla Lam.
O. ferruginea Royle
Subsp. cuspidata differs from subsp. europaea in that the fruits are smaller (0.5–1.2 cm long, vs. 1.0–3.5 cm in subsp. europaea), with a thin but oily flesh. Tree 5–10(–18) m. Leaves narrowly elliptic to elliptic, (3–)5–6(–9) × (0.5–)1–1.5(–3) cm; lower surface covered with silvery to rusty red scales. Green 2002. Distribution AFGHANISTAN; ANGOLA; BOTSWANA; BURUNDI; CHINA: Sichuan, Yunnan; CONGO (Dem. Rep.); EGYPT; ERITREA; ETHIOPIA; INDIA: Kashmir, Uttar Pradesh; IRAN; KENYA; LESOTHO; MALAWI; MAURITIUS; MOZAMBIQUE; OMAN; PAKISTAN; RÉUNION ; RWANDA; SAUDI ARABIA; SOMALIA; SOUTH AFRICA; SUDAN; SWAZILAND; TANZANIA; UGANDA; YEMEN; ZAMBIA; ZIMBABWE. Habitat Extremely variable, usually scrubby open areas, forest margins. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration Coates Palgrave 1990; NT540.
With such a huge range it is not surprising that hardy provenances of Olea europaea subsp. cuspidata should occur, but most of those currently in cultivation are apparently of South African origin, usually grown as O. africana, the small-fruited African Olive. Apart from a tree dating to 1948 at Berkeley, none are particularly big. There is a pruned-down specimen outside the Curvilinear Range at Glasnevin (accessioned in 1996) that is apparently thriving, with healthy dark foliage. In Portishead, Somerset there is a 6 m individual in the former garden of Tony Titchen, grown from seed distributed from Kirstenbosch where it occurs as an indigenous Afromontane forest tree (T. Titchen, pers. comm. 2007; Johnson 2007). It closely resembles a normal olive except that the leaves are narrower and perhaps more silvery on the underside, and the fruits are very small. They are an important food source for many frugivorous birds.
In eastern Africa, the African Olive is an important constituent of lower-altitude dry Afromontane forest, often growing with Juniperus procera. On the northern slopes of Kilimanjaro in Tanzania it forms large tracts of monodominant forest following mass regeneration from seed after a fire, and can become a large tree (Grimshaw 1998). Its hard wood is unfortunately excellent for both construction and fuel, with the consequence that it is becoming much reduced in its African range. Collections from elsewhere in the subspecies’ wide distribution would be interesting. Material in cultivation in North America under the name O. ferruginea is presumably of Asian origin. Stock of two different clones grown by Sean Hogan (pers. comm. 2008) originated from the olive collection of the University of California, Davis.