Burdekin Plum

I was introduced to the Burdekin Plum fairly soon after arriving in Townsville so I’ve known the fruit for twenty-five years or more, but somehow without getting around to eating one or knowing much about them.

That looked like it would change when we moved into a house that had a big tree in the neighbour’s yard, overhanging our roof, and the time has come: we had the tree trimmed last week and picked up a couple of buckets of fruit afterwards, too many to ignore.

History and botany

The Burdekin Plum, Pleiogynium timoriense, is native to coastal Queensland and its range extends through New Guinea, the Pacific Islands and Indonesia to Malaysia. It has been here, with surprisingly little change to the fruit, for at least thirty million years according to Andrew Rozefelds and Ngaire Kane whose article gives the best introduction to the species I have found.

Tuckerbush.com is also informative and notes that, “Burdekin Plum, also known as Tulip Plum, is an Australian native that produces plump, acidic fruits that are only edible when ripe. Though it is a rainforest species, it is incredibly hardy and drought tolerant. In the wild, it may also occur naturally on sand dunes behind mangroves and in dry sub-coastal regions along the northeast coast.” We don’t get much rainforest here in the Dry Tropics but I have seen them growing wild in the hills on Magnetic Island, and near the beach on the Town Common. There are several, for instance, in the carpark and picnic area at the old Quarantine Station.

The species is a member of the Cashew family, according to Wikipedia,
and its relatives include cashew, mango, sumac, marula, Peruvian pepper and pistachio. The fruit are not at all like plums inside. The stone is huge and the flesh is only a couple of millimetres thick – and it’s stuck to the stones even more tightly than clingstone peaches. It can be eaten fresh but is more often cooked, in which case the fruit is boiled and the stewed flesh used in jams, jellies, chutneys, etc, or added to fruit pies.

The middle plum in my photo has been chewed by a possum or bird and serves to show just how thin the flesh is.

Indigenous people have been eating Burdekin Plums for thousands of years, and the tree and its fruit entered European awareness very early. Cook and his party “ate this fruit at the Endeavour R., and Banks’s journal records that ‘these when gathered off the tree were very hard and disagreeable but after being kept for a few days became soft and tasted much like indifferent [i.e., not very good] Damsons.’” (My quotation is from Wild Food in Australia by AB and JW Cribb, 1975. The whole book is available online.)

Harvesting

Fruit ripens from April to October, according to Australian Rainforest Fruits and to Plants of Tropical North Queensland (both introduced in this post) but it tends to fall from the tree when it is a beautiful deep maroon colour but still hard. As Banks discovered, they are barely edible at that stage. When it is fully ripe the fruit is purple-black and the flesh is soft.

Indigenous people traditionally buried the fruit in sand or ash for a few days to ripen it. A more modern approach recommended to us was to put them in a paper bag in a cupboard. The Wikipedia article about the species says, “Fruit must be removed from tree to ripen for several days in a dark, damp place,” but “damp” is not mentioned anywhere else and our experience was that damp fruit went mouldy faster than it ripened. The paper bag was much better!

The gap of a few days between fruit-fall and edibility has probably contributed to the plum’s neglect as an edible native fruit. If one comes across a tree, any fruit that is ripe has been on the ground and (often) attacked by animals; if fruit is nearly ripe, it has to be picked and kept safe, which isn’t always convenient on, e.g., a bushwalking trip.

I wondered why a tree should adopt such a fruiting habit and the only theory I could think of was that it relied on ground-dwelling animals to disperse its seeds; and the only rainforest ground-dwelling rainforest animal I could think of that might be big enough to swallow the fruit whole was the cassowary. A little research (I love the internet) proved me right on both counts. This DES page gives a good account of how it all works.

Preparation and Consumption

Neither Cunningham, Tankard nor Norrington even mention the fruit in their books on tropical food gardening (see this post for details of their books)

When I asked on the helpful, enthusiastic Food for Thought – Townsville facebook group, I received responses ranging from bare awareness that they were edible, to voices of experience:

• I think they need to be buried in sand to ripen but I’ve only had them once. Would love to try again.
• I’ve tried and failed… eagerly awaiting the answer!
• Just know they are nice when ripe but not much flesh on the large woody seed. Have successfully germinated the seeds. Curious to try the recipes next time i get some fruit.
• A lady on Magnetic Island has the jam stall and makes the best burdekin plum jam!!
• Brown paper bag in the cupboard to help them ripen. I’ve made a cordial out of them before and subsequently a jelly (with regular gelatin.)
• They make a great conserve – goes well with cheese. A bit fiddly to make.
• From ‘Wabu jananyu’, my edible natives book by the Girringun Aboriginal Foundation: ‘We pick the fruits early and bury them in the sand for a few days to ripen them. Ngaguba can be eaten raw or used in jams. This is another prized fruit for us and we watch the trees and wait for the ngaguba fruit to be ready to be picked.’ There are green/white and the usual red fleshed versions.
• Burdekin plums can be eaten fresh, obviously, or sliced and added to fruit salads. They can be cooked down to make sauces or chopped up and used to make gravy for pairing with meats such as venison, kangaroo, and emu. Traditional jams, jellies, and wine go without saying. It can also be used in lieu of rhubarb in fruit pies such as strawberry and apple. No recipes sorry but when I get my hands on some, I’ll attempt a chutney.

The (equally helpful and enthusiastic) folk on Oz Rare Fruit didn’t have any recipes for me but a search through their old posts revealed a similar level of awareness of the tree, i.e., they knew it and knew that the fruit was edible only when really ripe. One creative person had successfully used it as a substitute for plums in sloe gin. Another had grown it as far South as Sydney.

In the end, I had three recipes for jam and none for anything else. I have already been cooking but will leave the recipes and my comments on the results for a separate post.