The upper photograph displays the red form of Slender Pigweed. The 'redness' of individual plants can be quite variable – this is particularly true of the leaves, which can vary from green with dark purple blotches to to brilliant red. The flowering panicles and spikes are most likely to assume a bright red color. Another species that is often more or less red, Amaranthus cruentus (Red Amaranth), is occasionally cultivated as a garden plant. This species has been known to escape from cultivation, although this is uncommon. Some authorities regard Red Amaranth as a cultivated form Slender Amaranth, or Amaranthus hybridus cruentus. However, Mohlenbrock (2001) considers Red Amaranth a separate species that has bracts about 2-3 mm. in length and staminate flowers with only 3 stamens, rather than the usual 5. Another similar species, Amaranthus retroflexus (Rough Pigweed), is somewhat stouter and has longer bracts (about 4-6 mm.) than Slender Amaranth. To my knowledge, Rough Pigweed doesn't assume a red form.