Purple amaranth is a "pigweed" that has been distributed around the world, favoring tropical areas. This species is considered a weed in Europe, Asia, and Africa (Nigeria and Mozambique, specifically). It has a negative impact on farms in Japan and Brazil and is considered one of the chief recurring weeds in crops there. It can outcompete commercial crops such as mulberries, cassava, pineapples, maize, and others. _Common_Name_ also has been reported as poisonous to livestock because of its high nitrate content. The weed can also outcompete native plants in grasslands and islands. In Africa, Central and North America, Asia, and the South Pacific Islands, it is eaten as a minor crop.

Once the weeds start to flower and fructify, it will be difficult to control them effectively. In fact, the best time to remove weeds is before flowering and fructification because the seeds will spread rapidly after that. So, it is necessary to remove weeds more often and to take precautions in advance next year. Purple amaranth is an annual weed, the following methods can control its growth effectively. Mulching: During the seed stage, covering with sawdust, straws or black mulches to effectively inhibit seed germination and the growth of the seedling. Generally, this method is used in winter or spring to inhibit the germination of weed in the soil. If the weeds have already flowered and fructified, this method can be used to isolate the seeds and the soil to prevent the seeds from falling into the soil. Pulling out: Before the weeds fructify, wear gloves or use tools to pull them out. If it is difficult to pull out weed due to dry soil, adding water to the soil helps to make it easy to remove the roots thoroughly. After pulling out the weed, deep tillage can be adopted to remove the residual roots. This method is especially effective for weeds that are in the seedling stage. Pruning: Pruning weeds before they fructify can effectively control the propagation of weeds, especially for annual weeds. Frequent pruning can inhibit the growth and fructification of weeds and effectively them in the same year. Plowing: Before cultivation, plow the soil, collect and discard the roots of perennial weeds, then expose them to the sun or bury them deeply. It can also be used for retting organic fertilizer and composting. Chemical control: Using appropriate herbicides can effectively remove the weed from the area. Note: When removing weeds, it is necessary to wear gloves to avoid direct contact with the weeds, especially for the ones that are poisonous, thorny and allergenic. When removing weeds at the flowering stage, special masks should be worn to prevent allergic reactions caused by the inhalation of pollen.