Olive

Olea europaea L. subsp. europaea

Olea europaea L. subsp. cuspidata

Synonyms - Olea cuspidata and Olea africana, the Wild or African Olive are now considered a single subspecies Olea europaea subsp. cuspidata.
Olea chrysophylla, Olea ferruginea, Olea sativa var. verrucosa, Olea verrucosa

Family: Oleaceae

Names:

Olea or the Greek 'elaia' or 'elea' is the classical Latin name for the Olive or its fruit.
Europaea refers to it origin in Europe.

Other Names:

Summary:

The Olive is an evergreen tree to 15 m high with a dense rounded crown. The opposite leaves are narrowly elliptic, 30-70 mm long, the upper surface is dark green and the lower surface silvery scaly. Olive has clusters of small cream to white flowers. Each flower is 5-10 mm in diameter with 4 spreading segments 3 mm long. The fruits are fleshy, elliptic in shape and 20-30 mm long, at first green but maturing purple to black. The seed is a stone contained in the fleshy fruit.
Native to the Mediterranean region, it is widely planted as a commercial crop in Australia and gradually becoming a severe bushland weed. There are numerous cultivars. It flowers in spring and summer.

Description:

Cotyledons:

Two. Longer and broader than the small radicle.

First leaves:

Leaves:

Opposite with pairs at right angle to those above and below.
Stipules - None.
Petiole - Short.
Blade - narrowly elliptic, 10-80 mm long x 3-20 mm wide, leathery, the upper surface is dark green and often glossy whilst the lower surface silvery scaly. Tip pointed. Sides rounded. Base tapering. Hairless.

Stems:

Erect tree to15 m high with a thick trunk and a dense rounded crown. Branches ribbed when young. The bark is initially smooth and pale silver grey to green becoming rough and grey or greenish black with age. Lenticels are conspicuous on young stems.
The stems are usually in a strict opposite arrangement and at right angles to those below (decussate).

Flower head:

Clusters of small cream to white flowers in short axillary or terminal racemes. The fruits are fleshy, elliptic in shape and 20-30 mm long, at first green but maturing purple to black. The seed is a stone contained in the fleshy fruit.

Flowers:

White, fragrant, 5-10 mm in diameter with 4 spreading segments 3 mm long. Usually bisexual.
Ovary - Superior. 2 celled with 2 ovules in each cell.
Style - Short, simple. Stigma - 2 lobed.
Calyx - 1-2 mm long with 4 short teeth.
Corolla - Small, white with a very short (1-2 mm) tube and 4 spreading segments 2-3 mm long.
Stamens - 2. Exerted. Attached near the top of the corolla tube.
Anthers - 2 celled, large.

Fruit:

Fleshy, elliptic in shape and 10-35 mm long x 6-20 mm diameter, at first green but maturing purple to black and containing a bony stone (endocarp) with 1-2 seeds. Stone is brown, oblong, 10-15 mm long and oily. The fruit is a drupe and very bitter before processing.

Seeds:

Straight embryo.

Roots:

Woody and branching. Forms a lignotuber.
Suckers readily from damaged roots and stump.

Key Characters:

Leave simple
4 corolla lobes
Ovule pendulous from summit of cell.
Albumen usually present
Fruit a large drupe
Adapted from John Black.
Subspecies europaea has leaves with a silver grey under surface, greenish white mid veins and leaf edges that are rolled under.
Whereas subspecies cuspidata has leaves with a pale brownish green under surface, yellowish green mid veins and the leaf tip is usually prominently hooked. .

Biology:

Life cycle:

Perennial evergreen tree.
Seeds germinate mainly in the autumn with some in spring. Passage of seed through animals or birds seems to stimulate germination. Initially it grows slowly and produces a large root system. It is usually about 5 years old when it first flowers and takes 10 years to mature and bear maximum quantities of fruit. Flowers are produced on the previous year's wood from October to November and the fruit ripens over summer. After fire or damage it will sucker or resprout. It is a slow growing species but very long lived with some plants estimated to be around 2000 years old.

Physiology:

Drought tolerant.
Frost and waterlogging sensitive.
Flowers develop on second year wood.

Reproduction:

By seed and suckers.

Flowering times:

Spring and summer in WA
October to November in SA, Victoria, WA

Seed Biology and Germination:

Seed germination appears to be enhanced by passage through bird or animal gut.

Vegetative Propagules:

Suckers.

Hybrids:

There are 2 subspecies, cuspidata and europaea and numerous cultivars.

Allelopathy:

Population Dynamics and Dispersal:

Long distance spread is by intentional plantings.
Local spread by birds and especially European starlings and ravens or animals including foxes eating the fruit and machinery.
Blackbirds, starlings, ravens, pigeons, magpies and noisy miners have been seen feeding on olives. Starlings accounted for over 90% of the seed dispersal in the Adelaide Hills.
Birds are the most important vector of spread.

Origin and History:

Native to the Mediterranean region and SW Asia.
One of the oldest cultivated plants in the Mediterranean area. It is a symbol of peace and on the United Nations flag.
The first recorded planting was on John Macarthur's Elizabeth Farm at Parramatta in NSW in 1805 and these trees are still present.

Distribution:

ACT, NSW, QLD, SA, TAS, VIC, WA.
Naturalised in China, Lord Howe Island, and North Africa.

Courtesy Australia's Virtual Herbarium.
It is widely planted as a commercial crop.

Habitats:

Lowland grassland, grassy woodland, dry sclerophyll forest, riparian areas and rocky outcrops.
Prefers full sun but will tolerate shade.

Climate:

Temperate, Mediterranean, semi arid to sub humid warm temperate regions usually with winter dominant rainfall and hot dry summers.
It is most invasive in areas with an annual rainfall of 500-800 mm.

Soil:

Tolerates most soil types except those that are waterlogged.

Plant Associations:

Significance:

Beneficial:

Commercial fruit crop for edible fruit, oil and medicines. Timber for carving, turning and supports in mines. Shelter for stock.

Detrimental:

Becoming a severe bushland weed.
Pollen causes hay fever.
It is the most serious woody weed of the Adelaide Hills.

Toxicity:

Not recorded as toxic.

Symptoms:

Treatment:

Legislation:

Noxious weed of SA when not planted for domestic or commercial purposes.
Sub species africana is a noxious weed in one part of NSW.

Management and Control:

Grazing normally provides control and it often becomes a problem after stock are excluded from an area.
Small plants can be hand pulled providing the roots don't break off.
For the cut stump method, cut down the tree and peel back the bark around the stump and immediately apply undiluted triclopyr + picloram or triclopyr.
For basal bark spraying mix 1 L triclopyr or triclopyr + picloram (e.g. Access®) in 10 L diesel and wet the lower metre of the trunk of the tree.
Remove some soil and drill directly into the lignotuber for drill and fill control.
Avoid applying herbicides in hot dry conditions.
Use the basal bark mix to treat any regrowth.
Glyphosate has not been very effective with these methods.

Overall spraying with 2,4-D680 or glyphosate450 at 1:100 can be used to control seedlings that are less than 6 months old. Use triclopyr600 or triclopyr + picloram at 1:50 for trees up to 2 metres tall. Use an organosilicone wetting agent with overall sprays.
Best control appears to be from applications made in late spring to early summer.
Replant with desirable species as soon as possible after control is achieved.
Planting Kangaroo Grass (Themeda australis) and using controlled spring burns has been effective at keeping previously infested areas Olive free.
Fire provides good control of seedlings but older plants will resprout.

Thresholds:

Eradication strategies:

Basal bark spray with a mix 1 L triclopyr + picloram (e.g. Access®) in 10 L diesel and wet the lower metre of the trunk of the tree. Repeat by spraying foliage with this mix if regrowth occurs.
Spray seedlings every second year with 10 L/ha triclopyr + picloram plus organosilicone adjuvant or spot spray until just wet with 10 mL triclopyr + picloram + 2.5 mL organosilicone adjuvant per 1 L water.

Herbicide resistance:

None reported

Biological Control:

Unlikely to be introduced because Olives are an important crop.

Related plants:

Olea paniculata is a native of NSW and Queensland.
Ligustrum lucidum (Broadleaf Privet)
Ligustrum sinense (Chinese or Small-leaf Privet)
Syringa vulgaris (Lilac)
Ash Trees

Plants of similar appearance:

Bullock-bush or Boonaree (Alectryon oleifolius).
Banyalla (Pittosporum bicolor)
Myoporum
Native Mock Olives (Notelaea spp.).
Oliveberries (Elaeocarpus spp.)
Phebalium
Native Correa seedlings look similar to Olive seedlings.
Olive Grevillia (Grevillea olivacea) has similar leaves.

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P685. Diagram.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Blood, K. (2001). Environmental weeds: a field guide for SE Australia. (CH Jerram & Associates, Australia). P22-23. Photos.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra).

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne).

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P. Diagram.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (2007). Western Weeds. A guide to the weeds of Western Australia. (Second Edition). Plant Protection Society of Western Australia, Perth, Western Australia. P198-199. Photo.

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne).#716.2, 716.3.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P570.

Moore, J.H. and Wheeler, J.R. (2013). Southern Weeds and their Control. (Second Edition). South Coast NRM and Department of Agriculture and Food Western Australia. P. Photos.

Muyt, A. (2001). Bush Invaders of South-East Australia: a guide to the identification and control of environmental weeds found in South East Australia. (R.G and F.J. Richardson, Australia). P241-243. Photos.

Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious weeds of Australia. (Inkata Press, Melbourne). P522-524. Photos.

Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P413.

Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P. Photo.

Wheeler, Judy, Marchant, Neville and Lewington, Margaret. (2002). Flora of the South West: Bunbury - Augusta - Denmark. (Western Australian Herbarium, Bentley, Western Australia). P725. Diagram.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.