Opuntia engelmannii and O. lindheimeri, are similar prickly pears, but there are also constant differences between these prickly pear cacti. We accept these opuntias as separate and distinct species. However, O. lindheimeri has been described as a variety of O. engelmannii by some authors. However you think of them (one Opuntia species or two), this checklist describes the differences.
- The younger pads of O. lindheimeri are less woody and “softer” or “greener” in appearance. Thus, the two opuntias appear different in overall aspect.
- O. engelmannii spines range from white, to tan, to yellow shades and brownish. O. engelmannii spines are seldom a rich canary yellow or shiny yellow. O. lindheimeri spines are almost always shiny yellow, whereas O. engelmannii spines are chalky and if yellow are dull.
- The base of O. engelmannii spines may be brown, or blackish, or even dark red-brown. Occasionally, plants are found with spine bases that are not darker than the spines. In contrast, the base of O. lindheimeri spines are seldom true brown or black but may be red-brown, dark plum, rust-brown, pink shades, or dark yellow.
- The annular markings of O. lindheimeri spines are more apparent than in O. engelmannii. The markings may not even be observable in O. engelmannii.
- O. lindheimeri fruits are narrower at the base or even vaguely pear-shaped; they tend to have a smooth surface and are typically red when newly ripe. O. engelmannii fruits are oval or roundish, darker (more purple or black-red) and less clear red in color, and with a more rugose (bumpy) surface. The umbilicus of O. engelmanni fruits is usually more depressed into the end of fresh fruit.
- O. engelmannii fruits are sweet and pleasant tasting, whereas those of O. lindheimeri are sour and not sweet. O. lindheimeri fruits are sometimes almost noxious.
- Plants with orange or red flowers occur occasionally (not often) in O. lindheimeri but are rare in O. engelmannii. Yellow flowers of either species may change to orange shades late in the day of anthesis or on the day after. Thus, the flower colors of these two opuntias can be different.
- O. lindheimeri is primarily a plant of Texas east of the Pecos River (extending into LA). In contrast, O. engelmannii is typically found west of the Pecos River to CA. If west of the Pecos River, O. lindheimeri grows in more mesic conditions than O. englemannii such as valley bottoms or partially shaded slopes.