Spinach is believed to have originated in ancient Persia (modern-day Iran) and later spread to China in the 7th century. It was brought to the United States around 1806.

Purslane is a common weed in North America even though it has roots in Africa and the Middle East. Purslane will grow in full sun in almost any soil and does best in warm weather. It prefers regular watering but can survive in drought; however, these weeds will die at the first freeze of the year

These weeds thrive in hot weather, can tolerate drought, respond highly to nutrients in the soil, and can adapt to avoid shading. This puts them in competition with warm-season vegetables. Most pigweeds can grow into large, erect-to-bushy plants anywhere from 2 to 7 feet high. There are over 60 different species of pigweed, which make their identification tricky.

Common lambsquarters is a summer annual broadleaf weed found in gardens, farmsteads, barnyards, roadsides, and row crops such as corn, soybean, sugar beet, and potato. It grows well in disturbed, fertile soils and emerges early in the season. It is a heavy seed producer; noted to produce an average of about 70,000 seeds per plant. Seeds can stay viable for over 20 years, so removing plants before they set seed is important.