Like the name suggests, the lemon aspen is part of the citrus family. The taste of its edible fruits has been described a mix between a grapefruit and a lime. It is known under the alternative name of rainforest lemon because it grows in jungles. This Australian species has its origin in North Queensland, as well as coastal areas all the way down to Sydney.
The scientific name of the species is acidula and comes from a Latin word meaning "a bit acid". Lemon aspen was first discovered and described by Ferdinand von Mueller, who was a Victorian state botanist.
Lemon aspen is just one of the popular names of the plant and fruit, which are also known as lemonwood or hard aspen. However, it is not a true aspen and unrelated to those that grow in the Northern Hemisphere, which are part of the genus Populus and the family Salicaceae that notably includes the willow. The lemon aspen is a member of the genus Acronychia and the rue family Rutaceae, related to the Citrus genus of the real lemon.
The species is important for its edible fruits, which grow in heavy clusters and are either green or white, with a diameter of 3-4 cm. The strong lemon flavour is combined with herbal notes that also resemble honey and eucalyptus.
The lemon aspen bloom starts at the end of summer, when the first white flowers appear. The berries become ripe during the autumn and winter and fall to the ground when mature. Shaking the branches is usually enough to easily harvest them. Lemon aspens enjoy full sun exposure in protected locations and are vulnerable to frost and strong winds. It grows best in sandy soils or other types with good moisture and drainage and doesn't do well in dry areas. The lemon aspen eaves have a length of about 25 cm and form dense and attractive green foliage.
The lemon aspen tree has a nice aspect and requires almost no maintenance, which makes it popular in gardens. It can reach a height of 12-15 m in a climate similar to its native rainforest habitat but no more than 6-7 m in other locations. With regular pruning, it is suitable for pot cultivation or as a hedge, similar to other citrus species.
Australian natives in north eastern Queensland depended on the fruits as a source of food. It is still popular in the state today and cultivation continues in the area. The Atherton Tablelands are the Queensland region where most production is located. It is grown on a smaller scale in parts of south east Queensland and northern New South Wales.
The Acronychia acidula fruit has a tart and acidic taste that makes fresh consumption quite uncommon, although it can be eaten out of hand when ripe. It is widely used as a cooking ingredient or as processed food. Just like its citrus relatives, the fruit juice and pulp are valuable in cooking, especially for sweet or savoury recipes.
The lemon aspen fruit also has cosmetic properties and its extract is an ingredient in products for skin care and repair, as well as a sunscreen and anti-aging agent. Similar to many native Australian fruits, the lemon aspen has much higher antioxidant content than most normal varieties. It is more potent than a blueberry, for example. The lemon aspen fruit provides large amounts of iron, zinc and folate, as well as some calcium and magnesium.
The flavour of the lemon aspen has been compared to a grapefruit. It is packed with vitamin C, a strong antioxidant that boosts the human immune system. Including it in your diet reduces the risk of flu and common cold.
The lemon aspen fruit can be consumed both fresh and cooked. It has a rich lemon taste, with intriguing hints of honey and eucalyptus. The fruits pair well with chicken and seafood or can be prepared as juice, cake, salad dressing, syrup or jam.
Since the taste is very similar to classic citrus fruits, the lemon aspen can replace them in most recipes. The fruit is an ingredient in syrups, juices, fruit wine, flavoured mineral water, cordials, confectionary and glace fruit. It is a very useful item in the food industry, where it is included in dressings, preserves, chutneys, sauces, mayonnaise, relishes and many sweet and savoury meals.
The lemon aspen is part of a large family of plants that includes both shrubs and trees with a strong aroma. They are found virtually in all parts of the world, including tropical areas like Australia or South Africa, and are widely cultivated for their fruits.
Lemon aspen is cultivated in Australia in small-sized plantations that specialize in bush food. These are located on the continent's East Coast, between North Queensland and the northern parts of New South Wales. Lemon aspen has a fast rate of growth, so pruning is mandatory in order to prevent it from reaching a height that would have harvesting difficult. When grown from seed it starts to produce fruits after four years and it has an average yield. It requires a lot of water when immature and should be planted in sunny locations, with soils rich in clay and loam with good drainage.
Like most bush fruits, the lemon aspen has become increasingly popular lately but cultivation remains limited. The fruits have economic value mostly because they are turned into quality jams, which share the acidic and spicy flavour of other citrus varieties. Even if some plantations have been established on the coasts of Queensland and northern New South Wales, most of the fruits for jams processing are harvested from the wild. For best results and fruit production, the tree needs moist and well drained soils, as well as sheltered locations with full sun exposure.
The lemon aspen tree grows in protected places in the wild because it is quite sensitive to strong winds. A windbreak should be built before starting a lemon aspen orchard, in order to provide shelter during flowering and fruiting, when the species is most vulnerable. It is also possible to plant native windbreaks, which provide a number of additional benefits. These create a habitat for insects that pollinate the tree as well as predators of harmful parasites. In addition, they reduce evaporation and increase local biodiversity.
There are several ways to improve the soil of commercial plantations in order to boost production. Applying a lot of organic matter on sandy soils is an excellent solution to make them retain more water in a natural way. Soils that are rich in clay, or those located in cooler climates, benefit from ripping and mounding in order to guarantee adequate drainage.
It is also a good idea to periodically mulch the rows. This will prevent soil erosion, increase the content of organic material, kill harmful weeds and improve water retention.
The lemon aspen can be propagated using either seeds or cuttings. Seeds are viable as long as they are fresh and don't need any additional treatment. In order to use cuttings, take them from the growth of the current year and make sure they are firm. It grows quickly and will start to produce fruits after about four years.