Mother Nature's Montrose Garden: November 2021

Western (Common) Yarrow (Achillea millefolium): good plant for fall

November can be interesting in Western Colorado; you just never know what the weather will bring. Last year we’d already had several snows in Mother Nature’s Montrose Garden by early November. This year it’s been unusually warm, leading to a great display of seasonal color. Next year, who knows!

Planning an interesting November garden can be a challenge, given such unpredictable conditions. Some of our best choices are plants that are hardy (and therefore stay green longer into the cold season) but also add interest in their dormant state. One such plant is our Plant of the Month, Western Yarrow or Achillea millefolia. The scientific name is pronounced uh-KILL-ee-uh mill-ee-FOH-lee um.

Western (Common) Yarrow (Achillea millefolium):in wild
Uncompahgre Plateau, Western Colorado

Yarrow grows throughout the western U.S., from the West coast to the Great Basin and Rocky Mountains. It grows in most of the western and central Colorado counties, but is uncommon or absent in the eastern Colorado plains. You’ll find it in numerous plant communities from the coastal strand of the Pacific to high mountain meadows (to 13,000 ft. in Colorado) and coniferous forests. In the wild it often grows in open meadows and grasslands along with native grasses, perennial herbs and bulbs (above). It often forms a natural groundcover between/beneath taller plants.

Western (Common) Yarrow (Achillea millefolium):growth habit

Yarrow is an herbaceous perennial that is 1-2 ft. tall and wide. In the first year or two it forms a mounded clump (above). But Yarrow spreads horizontally via rhizomes (horizontal underground stems), forming larger clumps and potentially filling an area.

Western (Common) Yarrow (Achillea millefolium):flowers

Yarrow is a member of the Sunflower family (Asteraceae), which makes sense when you look closely at the flowers. The dense, rather flat flowering clusters are composed of many tiny ‘sunflowers’ (see above photos). Plants bloom in the warm season, often from spring into fall. The flower color is usually white, but there are pastel pink or purple variants (below), which are the basis for several horticultural varieties (cultivars). Plant breeders continue to develop cultivars with flower colors that range from red, rust and orange to gold and yellow. Some of these are hybrids with European forms of Yarrow.

Western (Common) Yarrow (Achillea millefolium):natural color

Western (Common) Yarrow (Achillea millefolium): foliage

The foliage of Yarrow is pretty in its own right. The leaves are so finely dissected that they appear feathery or fern-like. They add an interesting texture and medium green color to the summer garden and are sweetly scented. They also remain green well into autumn, making them useful in a garden transitioning to winter.

Western (Common) Yarrow (Achillea millefolium):contrast in fall garden

Yarrow is an extremely adaptable garden perennial. It can be grown in most soils (including alkali) and tolerates everything from full sun to part-shade. You can even grow it in quite shady conditions, although it may not flower.

Yarrow is quite drought tolerant due to a relatively deep, fibrous root system; but it will die back to the ground under very dry conditions. It stays green from spring to fall with occasional water (Water Zone 2 or 3) or regular water (Zone 4; see https://www.slideshare.net/cvadheim/water-zone-gardening). This makes it a good plant for transitions between regularly watered parts of the garden (like lawns) and drier areas. We particularly like Yarrow as a filler plant in newly planted water-wise gardens. It provides needed color while trees and large shrubs are growing. It becomes a welcome groundcover once the larger plants mature.

Western (Common) Yarrow (Achillea millefolium): easy-to-grow perennial

Yarrow is easy to grow. We suggest that you taper off watering in fall, letting the plants die back a bit before winter. Fall is a good time remove plants that have spread too far – you can be absolutely ruthless tearing it out. You can also mow larger areas of Yarrow in fall or summer, if desired. Be sure to set your mower height to high – 4-6 inches – so you don’t damage the plants. After a short dormant period, plants will begin to grow again in the spring. Spring is another good time to dig out unwanted plants. You can re-pot these and give them away as gifts or use them in other parts of the garden.

Western (Common) Yarrow (Achillea millefolium): tiny seeds

Both the straight species and Yarrow cultivars are available as plants at most native plant nurseries. You can also grow Yarrow quite easily – and inexpensively – from seed, which is readily available from many native plant seed sources. Seeds can either be sown in prepared beds or grown up in containers for planting out. When seedling directly into the garden we suggest planting the seeds in late fall or winter, as seeds benefit from the cold exposure.

We like to start seed in containers (washed, recycled nursery pots work fine), then transplanting the plants into the garden. Many seed companies give their seeds a cold pre-treatment before shipping. You can also store your seed in a plastic bag in the refrigerator for better germination. Seeds can be planted in outdoor containers from mid- to late spring through early-summer, depending on your climate. The seeds are small, so sprinkle them on the potting soil and lightly cover with additional potting soil. Water them in - then be sure to keep the soil moist until seedlings develop.

Western (Common) Yarrow (Achillea millefolium): emerging seedlings

Western (Common) Yarrow (Achillea millefolium): larger
seedlings look more like Yarrow

Seeds will begin to germinate when the days start to warm, so don’t give up if your seeds don’t germinate right away. The picture above shows newly germinated Yarrow seeds. The seedlings will soon develop leaves that look more Yarrow-like. In about 2 months they will be ready to transplant into the garden.

Western (Common) Yarrow (Achillea millefolium): in mixed planting

So how to use Yarrow in the garden? Let me count the ways! The flowers are lovely in the summer garden and make nice cut flowers. It’s a great filler plant around shrubs. You can plant it in a mixed prairie or meadow planting. Or include Yarrow in more traditional mixed perennial beds and cottage gardens. Its flowers and foliage add welcome interest to the fall and winter garden. That’s one good reason to not cut the plants back in fall. You be glad you waited when you see the contrast between dried seed heads and winter snow.

Western (Common) Yarrow (Achillea millefolium): many traditional uses

Yarrow has many traditional uses. The flowers can be used to make an aromatic tea. Young leaves can be included in a salad – they are tart, so use sparingly. The entire plant can be used as a natural dye plant, producing shades of yellows and greens. The dried flowers, foliage and seeds are sweetly scented and can be including in fragrant potpourri and sachets. They are said to repel moths, houseflies and ants.

Yarrow has a long history of use as a medicinal plant. The leaves are effective at stopping the bleeding from minor cuts and scratches. The whole plant makes a variety of plant chemicals known to have anti-bacterial and anti-fungal qualities. As with any herbal medicine, you should be sure to learn about the precautions associated with it. This plant should be used sparingly, as allergies can develop.

Western (Common) Yarrow (Achillea millefolium): natural groundcover

Yarrow is a natural groundcover and can literally fill an area. This can be either good or bad, depending on your needs. Yarrow makes a wonderful groundcover, particularly in those difficult areas under trees that range from quite sunny to quite shady. It also works well on those hard-to-maintain slopes. Yarrow can be cut back – even mowed occasionally to 4-6 inches – to keep it as a non-flowering groundcover. Or you can mow some areas and leave others to flower. If you don’t want Yarrow to spread, it does well in pots/containers and planters if you divide it every other year.

Western (Common) Yarrow (Achillea millefolium): good choice
for an edibles garden

Old time gardeners included Yarrow in or around their edibles gardens. Yarrow is one of the best native plants for attracting beneficial insects and repelling ‘undesirables’. This is one reason why Yarrow was routinely planted – or left as a natural plant – around vegetable gardens and orchards in the past. Plant Yarrow near your vegetable garden and you’ll begin to see the benefits right away. Yarrow is also said to intensify the flavors of herbs planted near it.

Western (Common) Yarrow (Achillea millefolium): attracts
small native pollinators

Yarrow attracts some the smaller native pollinators – pollinator flies, small native bees and others. It occupies a habitat niche often not filled by other flowering plants. Plant it next to a seating area to watch these small visitors. The seeds of Yarrow provide food for winter birds. This is another reason to leave the plants unpruned until spring.

Western (Common) Yarrow (Achillea millefolium): at home
in medicinal garden

In summary, Yarrow is a great native plant for home gardens, large and small. It’s not only attractive but useful – a boon for those with small gardens. And it can be used as a lawn substitute or groundcover in larger gardens. There must be a spot, if only in a container, for some Yarrow in your garden.