Soursop, also known as graviola, is a fruit that comes from the Annona muricata tree, which is native to tropical regions of the Americas and the Caribbean but has since been cultivated in various other tropical climates around the world. It is in the same genus, Annona, as cherimoya and is in the Annonaceae family.
The soursop is adapted to areas of high humidity and relatively warm winters; temperatures below 5 °C (41 °F) will cause damage to leaves and small branches, and temperatures below 3 °C (37 °F) can be fatal. The fruit becomes dry and is no longer good for concentrate.
Soursop is widely promoted (sometimes as graviola) as an alternative cancer treatment, but there is no reliable medical evidence that it is effective for treating cancer or any disease.
Away from its native area, some limited production occurs as far north as southern Florida within USDA Zone 10; however, these are mostly garden plantings for local consumption. It is also grown in parts of China and Southeast Asia and is abundant on the Island of Mauritius. The main suppliers of the fruit are Mexico followed by Peru, Brazil, Ecuador, Guatemala, and Haiti.
The fruit is quite large, can be oval or heart-shaped, and has a green, spiky exterior. The flesh inside is white and creamy, with a texture somewhat like custard when ripe. Its flavor is a unique combination of strawberry and pineapple with sour citrus flavor notes, contrasting with an underlying creamy flavor reminiscent of banana or coconut.
The leaves are typically oblong to oval, sometimes lanceolate (lance-shaped), with a p ointed tip. They are glossy and dark green on the upper surface, while the underside can be lighter green or have a slightly paler hue. When crushed, soursop leaves can emit a characteristic aroma, which some describe as slightly musky or like the fruit itself, though this isn’t as pronounced as in some other aromatic plants.
The bark of a young soursop tree is smooth and can be greenish-brown or grey. As the tree matures, the bark becomes rougher, darker, and often has a more brown or greyish-brown appearance. Initially, the bark might be relatively smooth, but over time it develops a rough texture with longitudinal fissures or cracks. The bark isn’t overly thick compared to some other tree species. On younger stems or branches, you might notice small, raised, corky spots or lines known as lenticels. When cut, the inner bark or phloem layer, which is just beneath the outer bark, can be somewhat fibrous and might have a lighter color, often with a greenish tinge when fresh.
The flowers of the soursop tree are relatively large and can be quite conspicuous.There are three outer petals which are thick, fleshy, and yellowish-green or pale yellow in color. These petals can sometimes have a purplish or reddish base. Inside the outer petals, there are three inner petals that are smaller, thinner, and usually more yellowish. These inner petals form a sort of cone or dome in the center. The flowers emit a fragrance that can be described as sweet or musky.
The flowers are primarily pollinated by beetles, which are attracted by the scent and the somewhat fermented or yeasty odor the flowers can produce.The flowering can occur at various times of the year, depending on the climate, but often happens in cycles. In tropical climates, soursop might flower and fruit almost continuously or have several peaks throughout the year.
The soursop tree has a relatively shallow root system. Like many trees, it starts with a taproot when young, but this might not remain as dominant as the tree grows. These spread out from the base of the tree, seeking water and nutrients. They are fibrous and can spread quite widely but not deeply.
The flesh of the fruit consists of an edible, white pulp, some fiber, and a core of indigestible black seeds. The pulp is also used to make fruit nectar, smoothies, fruit juice drinks, as well as candies, sorbets, and ice cream flavorings. In many cultures, it’s also used in desserts, and its leaves are sometimes used for tea.
Facts About Soursop Tree
- Flowers can be used in salads, as infusions or as a garnish where they’re not the main component.
- Some laboratory studies have looked into soursop for its potential anti-cancer properties, particularly related to compounds like acetogenins. However, these studies are in early stages, and human trials are limited, so it’s not used as a cancer treatment.
- While soursop may have many potential benefits, it’s also worth mentioning that consuming large amounts, especially of the seeds or in extract form, might not be safe. There’s concern over long-term use potentially leading to neurological issues similar to Parkinson’s disease due to the presence of annonacin, a neurotoxin.
- It’s generally advised for pregnant or breastfeeding women to avoid soursop leaf products due to insufficient reliable information on safety.
- As with many herbal remedies, there could be interactions with medications. For instance consuming extracts in large amounts might affect blood pressure or blood sugar levels, so caution is advised if one is on medication for these conditions.
- The roots, like other parts of the soursop tree, contain various alkaloids and compounds. Their consumption or use in remedies should be approached with caution due to potential toxicity.
- As with any new food, there’s a risk of allergic reactions, especially if one is sensitive to other plants in the Annonaceae family.
Cultivation
Growing Soursop
Climate
Soursop thrives in tropical climates. It does not tolerate frost or very cold temperatures. Ideal temperatures are between 25°C to 28°C (77°F to 82°F). It can grow in subtropical areas if protected from cold winds and given a warm microclimate.
Soil
- Use well-draining soil rich in organic matter. A pH of 6.0 to 6.5 is ideal, though it can tolerate slightly acidic to neutral soils.
- Sandy loam or loamy soil that doesn’t retain excessive water is best to prevent root rot.
Planting
- Seeds: You can grow soursop from seeds, although trees might not produce fruit true to the parent plant. Seeds should be planted in seedling trays or pots with good drainage. Germination takes about 15-30 days.
- Grafting: For guaranteed fruit quality, use grafted plants. This ensures the tree will bear fruit similar to the parent tree.
Location
- Choose a sunny location. Soursop trees need plenty of sunlight, at least 6 hours daily.
- Ensure there’s enough space as the tree can grow up to 30 feet (9 meters) if not pruned.
Watering
- Water regularly to keep the soil moist but not waterlogged. Reduce watering in cooler months or if the plant shows signs of too much moisture.
Caring for Soursop
Fertilization
- Use a balanced fertilizer (like 10-10-10 NPK) every three months during the growing season. Organic compost or manure can also be beneficial.
Pruning
- Prune to shape the tree, remove dead or diseased branches, and to encourage fruiting. Pruning also helps to keep the tree at a manageable size for harvesting.
- Prune after harvesting the fruit to encourage new growth.
Pest and Disease Management:
- Common pests include mealybugs, scale insects, and fruit flies. Use neem oil or insecticidal soap for minor infestations.
- Root rot can be an issue if overwatered. Ensure good drainage to prevent this.
- Anthracnose, a fungal disease, can affect soursop. Use appropriate fungicides if signs appear.
Mulching
- Mulch around the base to retain soil moisture and reduce weed growth, but keep the mulch a few inches away from the trunk to prevent rot.
Harvesting
- Fruits are ready to harvest when they’re slightly soft to the touch and the skin yields to gentle pressure. The skin will still be green, but the spines will be spaced further apart and less sharp.
- Harvest with care as the fruit can bruise easily.
Pollination
- Soursop flowers are typically pollinated by beetles in their natural environment. In areas where these pollinators are scarce, hand pollination might be necessary to ensure fruit set.