Nature’s Notebook

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Photo for species Achillea_millefolium

Common yarrow, which was often used by Native Americans, has been used as a medicinal plant for over 3,000 years, and is still used today.

 

 

Photo Credit:
© William S. Justice. Courtesy of Smithsonian Institution, Dept. of Systematic Biology, Botany.

Achillea millefolium

common yarrow, yarrow (common), hierba de las cortaduras, milfoil, plumajillo, bloodwort, western yarrow, carpenter's weed
What does this species look like?
What does this species look like?: 

Common yarrow is an erect, perennial, herbaceous plant growing 8 to 40 inches tall, often having several plants joined by underground creeping stems. Its tiny, white (or sometimes pink) flowers occur as small flowerheads with many disk flowers that have both male and female parts and five ray flowers that are generally female; these small flowerheads are then grouped into showy, flat-topped clusters at the top of the plant. Flowers are insect-pollinated.

Common yarrow is found on slightly disturbed, well-drained soils, mostly in grasslands and dry meadows, canyon bottoms, open forests, and roadsides. It is moderately drought tolerant, and intolerant of dense shade.

Why observe this species?

Common yarrow is a USA-NPN regional plant species. Regional species are ecologically or economically important but are distributed more locally than calibration species. The USA-NPN integrates these observations to understand better plant responses within the different geographic regions of the nation.

Where is this species found?
States & Provinces: 
AB, AK, AL, AR, AZ, BC, CA, CO, CT, DC, DE, FL, GA, HI, IA, ID, IL, IN, KS, KY, LA, MA, MB, MD, ME, MI, MN, MO, MS, MT, NB, NC, ND, NE, NH, NJ, NL, NM, NS, NT, NU, NV, NY, OH, OK, ON, OR, PA, PE, QC, RI, SC, SD, SK, TN, TX, UT, VA, VT, WA, WI, WV, WY, YT
Special Considerations for Observing

If drought seems to be the cause of leaf senescence for a plant, please make a comment about it for that observation.

Which phenophases should I observe?
Leaves

Do you see...?

Initial growth
New growth of the plant is visible after a period of no growth (winter or drought), either from above-ground buds with green tips, or new green or white shoots breaking through the soil surface. Growth is considered "initial" on each bud or shoot until the first leaf has fully unfolded. For seedlings, "initial" growth includes the presence of the one or two small, round or elongated leaves (cotyledons) before the first true leaf has unfolded. More...

Leaves
One or more live, fully unfolded leaves are visible on the plant. For seedlings, consider only true leaves and do not count the one or two small, round or elongated leaves (cotyledons) that are found on the stem almost immediately after the seedling germinates. Do not include fully dried or dead leaves. More...

Flowers

Do you see...?

Flowers or flower buds
One or more fresh open or unopened flowers or flower buds are visible on the plant. Include flower buds that are still developing, but do not include wilted or dried flowers.

How many flowers and flower buds are present? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), simply estimate the number of flower heads, spikes or catkins and not the number of individual flowers.

Less than 3;3 to 10;11 to 100;101 to 1,000;More than 1,000

More...

Open flowers
One or more open, fresh flowers are visible on the plant. Flowers are considered "open" when the reproductive parts (male stamens or female pistils) are visible between or within unfolded or open flower parts (petals, floral tubes or sepals). Do not include wilted or dried flowers.

What percentage of all fresh flowers (buds plus unopened plus open) on the plant are open? For species in which individual flowers are clustered in flower heads, spikes or catkins (inflorescences), estimate the percentage of all individual flowers that are open.

Less than 5%;5-24%;25-49%;50-74%;75-94%;95% or more

More...

Fruits

Do you see...?

Fruits
One or more fruits are visible on the plant. For Achillea millefolium, the fruit is very tiny and seed-like and is crowded into a tiny spent flower head' The seed-like fruit changes from whitish-yellow or yellow-green to tannish and drops from the plant' Do not include empty flower heads that have already dropped all of their fruits'

How many fruits are present?

Less than 3;3 to 10;11 to 100;101 to 1,000;More than 1,000

More...

Ripe fruits
One or more ripe fruits are visible on the plant. For Achillea millefolium, a fruit is considered ripe when it has turned tannish and readily drops from the spent flower head when touched' Do not include empty flower heads that have already dropped all of their fruits'

What percentage of all fruits (unripe plus ripe) on the plant are ripe?

Less than 5%;5-24%;25-49%;50-74%;75-94%;95% or more

More...

Recent fruit or seed drop
One or more mature fruits or seeds have dropped or been removed from the plant since your last visit. Do not include obviously immature fruits that have dropped before ripening, such as in a heavy rain or wind, or empty fruits that had long ago dropped all of their seeds but remained on the plant.

How many mature fruits have dropped seeds or have completely dropped or been removed from the plant since your last visit?

Less than 3;3 to 10;11 to 100;101 to 1,000;More than 1,000

More...