American Yarrow Achillea borealis LinnaeusNon-native  Synonyms: Achillea aspleniifolia, Achillea millefolium var. occidentalis, Achillea occidentalis, Common Yarrow, Western Yarrow.

Status:

American Yarrow is a common wildflower that is found in dry open habitats and disturbed sites throughout Maryland. The taxonomy of American Yarrow is hotly debated. The US Forest Service website which uses the common name Western Yarrow explains the taxonomic confusion, "The scientific name of western yarrow is Achillea millefolium L. (Asteraceae). There are both native and introduced phases of western yarrow in North America. Introduced and native phases differ primarily in chromosome number and are difficult to distinguish morphologically. Native and introduced phases hybridize. The intricate pattern of morphologic, geographic, and ecologic variation within the species has frustrated all efforts to organize an intraspecific taxonomy on a circumboreal or even a strictly North American basis." There are many different cultivars of yarrow that are used in the horticulture trade. These cultivars come in a variety of colors including yellow and pink. Any yarrow that is observed that is not white should be considered a cultivar.

Description:

From the Ladybird Johnson Wildflower Center website: Yarrow grows to 3 feet tall and has no branches except near the top. The leaves are alternate, 3-5 inches long, with many leaflets on each side of the midrib (1- pinnately lobed); and these are further divided into smaller leaflets, giving them a delicate, fernlike, lacy appearance. Flower heads are arranged in large, compact clusters at the top of the stem, each cluster consisting of 1 or more flower heads. The flower head has 20-25 yellowish-white ray flowers and similarly colored disk flowers.

Where to find:

Look for American Yarrow along open roadsides and field edges across Maryland.

There are 457 records in the project database.

View species at Maryland Plant Atlas

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American Yarrow in Baltimore Co., Maryland (7/1/2012). Photo by Bill Hubick. (MBP list)

American Yarrow in Montgomery Co., Maryland (7/8/2016). Photo by Bonnie Bell. (MBP list)

American Yarrow in Caroline Co., Maryland (8/10/2016). Photo by Wayne Longbottom. (MBP list)

American Yarrow blooming in Anne Arundel Co., Maryland (5/23/2017). Photo by Tyler Bell. (MBP list)

American Yarrow (leaves and stem) in Anne Arundel Co., Maryland (9/18/2010). Photo by Bill Harms. (MBP list)

American Yarrow growing in Kent Co., Maryland (3/26/2016). Photo by Nancy Martin. (MBP list)

American Yarrow post-flowering in Wicomico Co., Maryland (9/2/2012). Photo by Bill Hubick. (MBP list)

American Yarrow in Harford Co., Maryland (4/29/2018). Photo by Josh Emm. (MBP list)


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