Plants of
South Australia
Olax obcordata
Olacaceae
Sweetheart Leaves
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Regional Species Conservation Assessments per IBRA subregion.
Least concern
Near threatened
Rare
Vulnerable
Endangered
Critically endangered
Extinct
Data deficient
Adelaide
Arkaroola
Ceduna
Coober Pedy
Hawker
Innamincka
Marla
Marree
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Oodnadatta
Renmark
Wudinna
Keith
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Botanical art

Kath Alcock painting: 1.

Etymology

Olax from the medieval Latin 'olax' meaning ill-smelling; referring to the wood of some Asiatic species which have an unpleasant odour. Obcordata from the Latin 'cordatus' meaning heart-shaped, with the prefix ob- (reversed), referring to the shape of the leaf.

Distribution and status

Endemic to South Australia and found on the western side of Kangaroo Island and three old records in the lower Eyre Peninsula, growing on sandy soil over sheet calcrete. Native. Rare in South Australia. Presumed extinct on Eyre Peninsula.
Herbarium regions: Eyre Peninsula, Kangaroo Island
NRM regions: Eyre Peninsula, Kangaroo Island
AVH map: SA distribution map (external link)

Plant description

A semi-parasitic perennial shrub to 1.2 m high with round, fleshy, yellow-green, inverted heart-shaped leaves and bronze stems. Flowers are white at the axis of the leaves, appearing in spring. Fruits are green, ovoid fruit to 7 mm long, with a persistent stalk. Seeds are round, pale yellow, woody seeds to 4 mm long.

Seed collection and propagation

Collect seeds between December and January. Thorough searching is required to locate the fruits as they are usually hidden between the leaves. Collect the fruits that are large and hard. No cleaning is required. Store the seeds with a desiccant such as dried silica beads or dry rice, in an air tight container in a cool and dry place. Seed viability is average for this species but this may depend on seed maturity when collected. This species is generally difficult to germinate, it has morphophysiological dormancy and complex germination requirements.

Fire Response

Obligate re-spouter and re-seeder. Seedlings observed as well as basal resprouting from burnt plants.

Longevity: >20 years

Time to flowering: 2 to 3 years

Recovery Work

In 2020-2021 this species was assessed post-fire in 1 year and 2 year old fire scars. A total of 1,900 seeds have been collected & banked for a population outside the 2020 fire scar. Further populations will be assessed and seeds collected on Kangaroo Island in 2021–2022. Germination screening testing the response to fire cues will be undertaken in 2021.This project was supported by the Project Phoenix program.

Seeds stored:
  Hide
LocationNo. of seeds
(weight grams)
Number
of plants
Date
collected
Collection number
Collection location
Date
stored
% ViabilityStorage
temperature
BGA430 (8.65 g)515-Dec-2008DJD1380
Kangaroo Island
1-Jan-201220%-18°C
BGA 
MSB
900 (21 g)
1,000 (23 g)
100+17-Dec-2015TST1269
Kangaroo Island
2-May-201770%-18°C
Location: BGA — the seeds are stored at the Adelaide Botanic Gardens, MSB — the seeds are stored at the Millennium Seed Bank, Kew, England.
Number of plants: This is the number of plants from which the seeds were collected.
Collection location: The Herbarium of South Australia's region name.
% Viability: Percentage of filled healthy seeds determined by a cut test or x-ray.