The Garden Ecology Lab’s Pollinator Plant PR Campaign Presents….. Yarrow!
The Garden Ecology Lab is releasing a series of plant profiles of the top 10 Oregon native plants for pollinators, based on Aaron Anderson’s 2017-2019 field trials of 23 Oregon native plants. We will feature one plant per week for 10 weeks, this is week 1! Profiles will include photos, planting information, and will highlight common pollinators of each plant.
- Scientific Name: Achillea millefolium
- Life Cycle: Perennial
- Growth Habit: Upright, spreading
- Bloom Duration: June – October
- Hardiness Zone: 3-7
- Special Traits: Drought tolerant, deer resistant
- When to plant: Starts can be planted in the spring or fall.
- Yarrow provides both nectar and pollen to its insect visitors.
- Yarrow was found to be associated with two species of Andrena in Aaron’s research (Andrena cerasifolii, A. candida).
- Andrena is a genus of early summer mining bees!
- Other common visitors to yarrow include sweat bees, nomad bees, and butterflies!
- Yarrow inflorescences provide a great “landing pad” for pollinators- they can rest directly on the plant while they forage.
Yarrow’s Native Range in Oregon
In Oregon, we have our own native variety of yarrow: Achillea millefolium var. occidentalis. Western yarrow's native range covers the entire state of Oregon. Map acquired from USDA Plants Database. Copyright 2014 © ESRI
Yarrow as a pollinator plant
Yarrow is a ubiquitous North American native plant: its range extends from Alaska to Florida and every state and province in between! Though it commonly appears on pollinator planting lists, many people are not convinced that it’s a great bee plant, because it is not typically buzzing with activity like we may see on Goldenrod or Douglas Aster. Instead of hosting an abundance of visitors, yarrow supports a high diversity of insect visitors.
Infographics developed by LeAnn Locher, Aaron Anderson, and Gail Langellotto.
Abundance and Diversity Calculations. Bee abundance was calculated using estimated marginal means of bee visitation to each of our study plants from 5-minute observations conducted from Aaron's 2017-2019 field seasons. Estimated marginal means (EM Means) were assigned categorical values and averaged across years to yield the following categories: 0% = Very Low =EM mean below 0.49; 25% = Low = EM mean of 0.50 to 0.99; 50% = Moderate = EM mean of 1 to 1.49; 75% = High = EM mean of 1.50 to 1.99; and 100% = Very high = EM mean above 2.0. Bee diversity was based on the total sum of species collected on each of our study plants from 2017 to 2019. A Chao 2 Estimator was used to estimate total expected species richness for each plant; Chao 2 estimates were then used to create categorical values, as follows: 0% = Very Low = 9.99 or lower; 25% = Low = 10 to 14.99; 50% = Moderate = 15 to 19.99; 75% = High = 20 to 24.99; 100% = Very high = 25 or higher.
Although yarrow doesn’t buzz with activity like some pollinator plants, it’s certainly not a flower to ignore! Yarrow is a hardy and low maintenance perennial that establishes and spreads readily in gardens. It’s a beautiful cut flower and can also be dried to include in longer lasting floral arrangements; its foliage that maintains its aromatic scent even after drying. Yarrow is additionally a wonderful plant medicine that has been used for centuries.
Did you know?
Yarrow has naturally-occurring pink variants! It can vary from pale pink (left), to deeply magenta (right). These plants were started from seeds collected from wild populations of yarrow, so we can be certain it is indeed a natural variation, rather than a true hybrid or cultivar! Another fun fact: "millefolium" translates to "thousand-leaved", which is a reference to its dissected leaves!
Photos from the field
Tune in next week for the next edition of our Pollinator Plant PR Campaign.