The medicinal parts of yarrow are the aerial parts, meaning everything above the soil: flowers, leaves, and stems. All three contain active compounds, but the flowers and leaves carry the highest concentrations of the plant’s therapeutic ingredients. The stems are typically included when harvesting but contribute less potency on their own.
Flowers and Leaves Are the Most Potent Parts
Yarrow’s flower heads and leaves each bring something slightly different to the table. The flowers are particularly rich in flavonoids, with the main active constituents being apigenin and luteolin. These compounds support the body’s ability to repair skin cells and reduce inflammation. The flowering tops also contain volatile oils that give yarrow its distinctive scent and contribute to its medicinal profile.
The leaves hold their own, carrying a mix of tannins, bitter compounds, and mucilage alongside vitamins and minerals like potassium and copper. Tannins are astringent, which is partly why yarrow has been used on wounds for centuries. The bitter compounds in the leaves act as a digestive tonic, helping stimulate bile flow and support overall gut function. Some subspecies of yarrow also contain rutin in their leaves, a flavonoid known for strengthening blood vessels.
The stems are generally less concentrated in active compounds, but because yarrow is almost always harvested and dried as whole stalks, they end up in most preparations by default. You’re not losing anything by including them, but if you’re making a tea or tincture and want maximum strength, prioritizing flowers and leaves is the way to go.
What These Parts Actually Do in the Body
Yarrow’s reputation in herbal medicine rests on a few key properties: wound healing, digestive support, and anti-inflammatory effects. The flavonoids in the flowers and leaves promote circulation and help skin cells regenerate, which is why yarrow shows up in ointments and creams for cuts, scrapes, and minor skin irritation. The tannins tighten tissue and help slow bleeding, a use so well known that yarrow’s Latin name, Achillea millefolium, references the myth of Achilles using it to treat soldiers’ wounds.
For digestion, the bitter compounds found throughout the aerial parts have a long history of use for stomach pain, bloating, diarrhea, and constipation. These bitters may help stimulate digestive secretions, and the plant’s alkaloids appear to have gastroprotective properties, potentially shielding the stomach lining from irritation. Yarrow has traditionally been used for ulcers and irritable bowel syndrome, though most of the evidence for these uses comes from historical practice rather than large clinical trials.
When to Harvest for Maximum Potency
Timing matters if you’re growing or wildcrafting your own yarrow. Leaves are at their peak right before the flowers bloom, typically in late spring or early summer. At this stage, the plant’s energy is still concentrated in the foliage rather than being diverted into flowering. Once the flowers open, they become the star of the show, and that’s the ideal time to harvest the flowering tops.
Morning is the best time to pick, after the dew has dried but before the heat of the day. Volatile oils, which carry much of yarrow’s medicinal activity, are at their highest concentration during this window. If you wait until afternoon, some of those oils will have evaporated.
How the Medicinal Parts Are Typically Used
The most common preparation is tea, made by steeping dried flowers and leaves in hot water. A traditional guideline suggests up to 4.5 grams of dried herb per day for issues like poor appetite, bloating, or mild inflammation, though this comes from traditional use rather than clinical dosing studies. One documented case linked drinking five cups of yarrow tea daily for a week with adverse effects, so moderation is reasonable.
Tinctures concentrate the plant’s compounds in alcohol, extracting a broader range of active ingredients than water alone. Topical preparations like salves and creams use yarrow’s circulation-boosting and anti-inflammatory properties for skin issues. In all of these forms, the flowers and leaves are the primary material. You’ll rarely find a yarrow product made from roots alone, because the therapeutic compounds are overwhelmingly concentrated in the parts of the plant that grow above ground.
A Note on Allergies
Yarrow belongs to the Asteraceae family, the same plant family as ragweed, chamomile, and chrysanthemums. If you have known allergies to any of these plants, yarrow may trigger a similar reaction. This applies regardless of which part of the plant you use, since the allergenic compounds are present throughout the aerial portions.