Solidago altissima

Solidago altissima is one to two meters (40-80 inches) tall, with fine hairs on the stem. The leaves are located along the stem, not in a rosette near the ground. One plant can produce as many as 1500 small yellow flower heads in a large conical array.[3]

Solidago altissima is self-incompatible, meaning that the pollen from one plant cannot pollinate the female flower parts of the same plant.[4]

Solidago altissima has diploid, tetraploid, and hexaploid populations and morphological variations which has generally led to classifying it into two subspecies, which roughly speaking can be identified as being from the eastern and western parts of the continent. At least in the Midwest, it is common to have plants of different ploidy interspersed, with little apparent tendency for one type to dominate even a fairly local geographical area.[4]

Within Solidago, S. altissima is part of the Solidago canadensis species complex, which is classified in the subsection Triplinervae.[4] S. altissima has sometimes been classified as part of S. canadensis.[3]

Subspecies[1][3][7]

• Solidago altissima subsp. altissima: This is the autonym subspecies. It is in eastern Canada except Newfoundland and Labrador, and it is in the provinces of Saskatchewan and Manitoba.[8] In the United States, it is east of the Mississippi River except Wisconsin, Illinois, and North Carolina; all U.S. states directly on the west of the Mississippi River; and, Nebraska, Kansas, Oklahoma, Texas, Utah, Arizona, and California.[8] In Mexico, it is in the north except on the Baja California Peninsula, Sonora, and Sinaloa.[8] It is in all other states as far south as Oaxaca and Veracruz except Mexico, Morelos, Puebla, Tlaxcala, and Mexico City.[8] It is native in all of the above states and provinces where it resides.[8] It is an introduced species in East China, South Central China, Korea, New South Wales, Taiwan, and Transcaucasus.[8]

• Solidago altissima subsp. gilvocanescens (Rydb.) Semple: This subspecies is in western Canada and Ontario.[9] In the United States, it is only east of the Mississippi River in Illinois, and is then distributed west through the Great Plains states.[9] In Mexico, it overlaps subsp. altissima except in the west.[9]