Lang Son, with its unique topographical conditions, is home to many famous products. One of the Lang Son's specialties that cannot be overlooked is the custard apple. Lang Son custard apples are renowned across the country not only for their beautiful appearance but also for the distinctive quality of the fruit. 

Lang Son custard apple has a fruit diameter of 74.3 mm or more, a fruit height of 75.02 mm or more, a weight of 268.15 g per fruit or more, an edible portion ratio of 42.33% or more, and a Brix level of 11.2 degrees or more. 

Specific characteristics and qualities of Lang Son custard apples are a result of their adaptation to the natural conditions of the geographical area. This area features a landscape of valleys and limestone mountain slopes, with soil types consisting of red-yellow and red-brown soils on limestone. The nutrient composition of the soil includes: average total nitrogen of 47.87 mg/kg, average total phosphorus of 135.55 mg/kg, average total potassium of 0.03 mg/kg, average available phosphorus of 130.32 mg/kg, average available potassium of 0.02 mg/kg, average cation exchange capacity of 2.56 cmol+/kg, average magnesium (Mg2+) of 1.21 mg/kg, and average sodium (Na+) of 0.94 mg/kg.
Lang Son's custard apple variety has the scientific name Annona squamosa Linn. The origin of the variety is controlled through a pedigree record. The propagation process is carried out in the geographical area using seed propagation methods. The local people choose land in the limestone mountainous region with good drainage to cultivate this specific product. After three years of planting, the first harvest will take place; in the following years, the local people will harvest in two seasons (main season: from July to the end of August, intercropping season: from the end of October to the end of December). 

The geographical area includes: Chi Lang town, Dong Mo town, Bac Thuy commune, Bang Huu commune, Bang Mac commune, Chi Lang commune, Gia Loc commune, Hoa Binh commune, Mai Sao commune, Nhan Ly commune, Thuong Cuong commune, Van An commune, Van Linh commune, Van Thuy commune, Y Tich commune in Chi Lang district; Huu Lung town, Cai Kinh commune, Dong Tan commune, Dong Tien commune, Ho Son commune, Hoa Binh commune, Hoa Lac commune, Hoa Son commune, Huu Lien commune, Minh Son commune, Minh Tien commune, Nhat Tien commune, Quyet Thang commune, Son Ha commune, Tan Thanh commune, Thanh Son commune, Van Nham commune, Yen Binh commune, Yen Son commune,  Yen Thinh commune, Yen Vuong commune in Huu Lung district, Lang Son province. 

Source: Bảo hộ chỉ dẫn địa lý "Lạng Sơn" cho sản phẩm quả Na 
Translator: Nguyễn Hải Phong