Yarrow is a plant that has been used for centuries in traditional medicine. It is also commonly known as achillea, bloodwort, carpenter's weed, devil's nettle, nosebleed, old man's pepper, staunchweed, thousand-leaf, and wound wort (among other names). But, does it work for the wide variety of elements it's been used to treat? As is common with herbal supplements, we don't yet have enough research to say for sure. However, preliminary studies do show promise for this herb in multiple areas. The flowering portion of the yarrow plant is what is typically used for medical purposes. Yarrow isn't just a single plant, though—the name is applied to about 140 different but closely related varieties that fall into the genus Achillea. Yarrow plants have been researched for a wide range of health problems and ailments that it has been traditionally used for. The following uses all have some studies associated with them. However, most of them have been performed on animals or on cells. Human trials, so far, have been rare. That means research is in its early stages and the findings have to be replicated in larger and more in-depth studies before we know for certain what medicinal benefits yarrow has—and how safe a treatment it is. Inflammation A 2017 review of the medical literature on the yarrow plant called achillea millefoilum L. listed several medicinal uses of the plant that have shown promise in studies. One of those uses is as a topical anti-inflammatory. Multiple studies support its anti-inflammatory action. A 2017 paper in The Journal of Ethnopharmacology said it had an "evident anti-inflammatory property" with a positive impact on the pH balance of the skin and its moisture content. Wound Healing Achillea millefoilum and achillea asiatica both have had positive preliminary results in a topical application for wound healing. In a 2017 study on achillea asiatica extract, researchers concluded that the herb was effective at improving skin wounds in rats through multiple effects at the cellular level. A 2018 study in the Journal of Maternal-Fetal Neonatal Medicine demonstrated a positive effect of achillea millefolium ointments on the healing of episiotomies. (An episiotomy is a small incision in the perineum that doctors sometimes make during childbirth.) Digestive Disorders A study out of Africa demonstrated an anti-spasmodic effect of achillea millefolium L. in part of the digestive system, which means it may be beneficial in conditions that involve spasms in the digestive tract, such as irritable bowel syndrome. Anxiety A 2015 review of the anti-anxiety properties of essential oils found that two varieties of yarrow—achillea umbelata and achillea wilhemsii—did appear to help lessen anxiety. Researchers said it appeared to have this effect with a different mechanism of action than the popular anti-anxiety drug class benzodiazepines. Neurological Conditions A 2017 study out of Iran supports the use of achillea millefolium in neurodegenerative disease, including multiple sclerosis, Parkinson's disease, stroke, and epilepsy. This conclusion is based on findings in animal studies. In multiple sclerosis, researchers say the supplement lessened disease severity, lowered neuroinflammation, and reduced the number of demyelinating lesions. In Parkinson's, they say it improved motility and muscle tone. In strokes, it appeared to reduce the infarct volume, and in epilepsy, it reduced the seizure severity. Other Possible Benefits The 2017 review and other studies support yarrow's effectiveness for: Immune-system support Regulating blood sugar in diabetes Protecting the liver and gallbladder Stimulating menstruation Helping with sleep Treating hemorrhoids Alleviating hay fever Speeding elimination of urine Possible Side Effects You may think that, because it's a "natural" product, yarrow supplementation is low risk or risk-free. Keep in mind that even natural substances can have dangerous side effects and drug interactions and treat them as you would pharmaceutical drugs. Yarrow is generally considered safe to use medicinally. Possible side effects may include: Drowsiness Increased urination Skin irritation when used topically (such as for wound healing) However, some groups of people may face more serious risks from taking yarrow supplements. Slowed Blood Clotting Yarrow is suspected of slowing blot clotting. That can be a problem, though. For instance, it's recommended that you stop taking it at least two weeks before a scheduled surgery. If you need emergency surgery, make sure the medical staff knows of this potential risk. In addition, it could be dangerous for people with bleeding disorders, as it may increase the risk of bleeding. DAYS TO GERMINATION:10-14 days at 65-72F (18-22C). SOWING:Transplant (recommended): Sow 8-10 weeks before last frost. Do not cover seed as light is required for germination. Bottom water or mist lightly to avoid covering the seed with displaced soil. Transplant to cell packs or 2-4" containers when the first true leaves appear, approximately 3 weeks after sowing. Harden off and transplant outside after the last frost. Direct seed: Sow seed in late spring, after late frost, early summer, or fall. Thin to stand 12-24" apart. Support may be necessary. GROWING ON:Grow seedlings for 3-5 weeks at 70-72F (21-22C) in full light. LIGHT PREFERENCE:Sun. SOIL REQUIREMENTS:Any well-drained soil. PLANT SPACING:12-24". HARDINESS ZONES:Zones 2-9. HARVEST:Fresh: Harvest when pollen is visible on the flowers. Cut in the coolest part of the day. USES:Excellent cut or dried flower. Permanent beds and mass plantings.