Wildflower/Perennial
Common yarrow
Achillea millefolium · Asteraceae
Also called: Yarrow, Milfoil, Western yarrow, Soldier's woundwort
Common yarrow (Achillea millefolium) is a low-water wildflower/perennial well suited to Tucson and the low desert. It thrives in full sun.
Common yarrow at a glance
- Water use
- Low (established)
- Sun
- Full sun; tolerates light afternoon shade in the low desert, which helps it through peak summer heat.
- Mature size
- 1-3 ft tall in bloom and spreading 1-2+ ft wide via rhizomes.
- Growth rate
- Fast; can be aggressive/spreading where well-watered.
- Bloom
- Flat-topped clusters of white (wild form) or, in cultivars, yellow, gold, pink, red, salmon, or terracotta., Late spring into summer in Tucson, with possible rebloom in fall if deadheaded; tends to slow in peak heat.
- Cold hardiness
- Very cold-hardy and frost-tolerant in USDA 9a-9b; tops may brown in summer heat but the plant is durable.
- Soil
- Highly adaptable; thrives in lean, well-drained soils and tolerates poor, rocky, alkaline Tucson soils. Avoid wet, heavy ground.
- Native range
- Circumboreal/Northern Hemisphere; native forms occur across much of North America including parts of Arizona's higher elevations, but it is not a low-desert Sonoran native. Most landscape forms are non-native cultivars.
- Best used as
- Pollinator garden, Xeriscape and low-water beds, Groundcover/filler, Cut and dried flowers, Erosion control
- Wildlife
- Attracts bees, butterflies, hoverflies, and other beneficial insects; ferny foliage is deer- and rabbit-resistant.
- Toxicity
- Mildly toxic - can cause skin photodermatitis/contact dermatitis in sensitive people, and is mildly toxic to dogs, cats, and horses if eaten (vomiting, drooling). Flag for pet households; low risk to kids.
How to grow Common yarrow in Tucson & the low desert
Watering
Drought-tolerant once established. Water deeply every 7-10 days in summer and every 2-3 weeks in winter; let soil dry between irrigations. Overwatering causes floppy growth and root rot.
Fertilizer & nutrients
Very low needs. Little to no fertilizer required; a light spring compost top-dressing is plenty. Rich soil makes it flop and spread aggressively.
Pruning & care
Deadhead spent flower clusters to encourage rebloom and prevent excess reseeding; shear back after bloom and cut down old foliage in late winter. Divide clumps every 2-3 years to keep vigorous.
Notes
Tough, ferny-leaved perennial that spreads by rhizomes - give it room or contain it. Keep it lean and on low water for the best, least floppy form in Tucson. Colored cultivars are showier than the white species.
Sources: University of Arizona Cooperative Extension / Pima County Master Gardeners; USDA NRCS PLANTS Database; ASPCA toxic/non-toxic plant list