Yarrow: A perennial that can handle Heat, Drought & Poor Soil

If you are sitting on our front porch, you can't help but notice the industrious little ants scurrying across the flagstone walkway (Piper, our youngest Sheltie, finds them fascinating and likes to poke at the tiny black ants with his nose). There are actually two ant colonies–one at the far end of the pathway and one a little closer to the porch.

I prefer not to wage war on the creatures with whom I share my garden, but this feeling of goodwill was challenged a few summers back when one of my favourite phlox began to die mysteriously one stem at a time. A quick investigation revealed it was the ants and their earth-moving ways. I refuse to resort to pesticide, so I began to experiment with plants that might live in harmony with the two well-entrenched colonies.

Yarrow in my garden.

That brings me to the main subject of today's post–Yarrow. Yarrow was one of the few plants that seemed to survive the ant's constant excavations (sedum groundcovers are another). The Yarrow actually seems to appreciate the sharp drainage provided by the sandy soil the ants bring up to the surface.

Yarrow is a tough, drought-tolerant perennial that likes a hot, dry, sunny location. Unlike so many perennials that like rich fertile soil, Yarrow is quite happy in average to poor soil (provided there is good drainage). If your garden soil is too rich, you may actually find that your yarrow flops.

Full sun is essential. Too much shade and Yarrow can become leggy.

Mid-summer Yarrow produces a profusion of round, flat blooms that are composed of tiny, daisy-like flowers. Colors include yellow, pink, cream, peach, terra cotta, red and maroon.

Yarrow makes a great, long-lasting cut flower. It's also a great everlasting flower that can be hung to dry. Simply cut your flowers (morning is best) and tie them with a bit of twine. Hang them in a cool, dry place out of direct sunlight until the flowers are dry to the touch.

One final reason to grow Yarrow–bees and butterflies love this flower!

Growing Yarrow from Seed

Plant Yarrow seeds indoors six to eight weeks before the last frost date. Sow seeds on the surface of moist potting soil and gently press down. Place the tray in a warm, sunny location in the house. Your seeds should germinate in two to three weeks.

Myself, I prefer to buy small potted plants in the spring. Yarrow may bloom that first summer, but I find it takes a full season to really get established.

Achillea millefolium 'Cerise Queen' in my garden.

Growing Yarrow

The most important factor in being successful with growing Yarrow is giving it the conditions it requires; full sun, good drainage and average to poor soil. If your soil is heavy, add some organic matter and even some fine pebbles to improve the drainage.

Water well until your yarrow is established. Once it has settled in, you'll find Yarrow is very drought tolerant and may only require supplemental water during times of extreme drought.

Unlike most perennials, Yarrow doesn't require any fertilization.

Yarrow can look rather tired after it flowers. I've found it's best to cut the whole plant back hard. It will look awful for a couple of weeks, but you'll be rewarded with fresh green growth and maybe even a second flush of flowers in late summer/early fall.

Divide Yarrow every three to five years in the early spring or in the fall.

Pests and Diseases

Yarrow is pretty resistant to pests, but aphids can occasionally be an issue. A good blast of water from the hose can dislodge the aphids. If the problem persists, you can use an insecticidal soap.

Powdery mildew and rust can also pose a problem. To eliminate the possibility of mildew, avoid watering the foliage, if possible, and allow for good air flow between plants.

Achillea millefolium 'Strawberry Seduction'

Invasive Tendencies

Common Yarrow, Achillea millefolium can be invasive and is considered by many to be an aggressive weed. Underground rhizomes can colonize a flowerbed and will sometimes even spread to the grass.

Achillea millefolium was introduced to North America in colonial times from Europe and Asia. Since that time it has escaped from gardens to naturalize along roadsides and in fields.

To control Yarrow's wandering ways, pull up any of the wandering underground stems in the spring just after it rains (the ground is softer after a rainfall). To eliminate the plant's spread by seed, deadhead the flowers before they set seed. Yarrow seeds remain viable for years!

Different Yarrows to watch for:

While the species plant Achillea millefolium spreads by underground rhizomes, many of the modern cultivars and hybrids have improved features like stronger stems, larger flowers and clump-forming habits.  

I have made a note in each of the descriptions below as to which varieties are clump-forming and which types are more likely to wander. 

Achillea 'Moonshine' is a classic Yarrow that has pale yellow flowers and silver-grey, fern-like foliage. This cultivar is non-spreading and makes a nice clump. Full sun. Height: 45-60 cm (18-23 inches), Spread: 30-60 cm (12-23 inches). USDA zones: 3-9.

A closer look at the foliage of Achillea 'Moonshine' 

Achillea 'Little Moonshine' is a shorter version of 'Moonshine'. It has the same canary-yellow flowers and silver-grey foliage but on a dwarf plant. This cultivar is also non-spreading and makes a nice clump. Full sun. Height: 30-35 cm (12-14 inches), Spread: 35-40 cm (14-16 inches). USDA zones: 3-9.

Achillea millefolium 'Hoffnung' has yellow flowers that fade to cream and green fern-like foliage. This cultivar is inclined to spread, so locate it carefully. Full sun. Height: 50-60 cm (20-23 inches), Spread: 45-60 cm (18-23 inches). USDA zones: 3-9.

Achillea Anthea is a British hybrid that has yellow flowers tinged with peachy-orange and silver-grey foliage. This cultivar has a non-spreading habit. Full sun. Height: 30-45 cm (12-18 inches), Spread: 30-45 cm (12-18 inches). USDA zones: 2-9.

Achillea millefolium 'Little Susie' has rose-pink flowers and green fern-like foliage. This cultivar is inclined to spread so reduce the size of the clump each spring. Full sun. Height: 30-45 cm (12-18 inches), Spread: 45-60 cm (18-23 inches). USDA zones: 2-9.

Achillea millefolium 'Saucy Seduction' has reddish-pink flowers and green fern-like foliage. This cultivar has a spreading habit. Full sun. Height: 50-65 cm (20-25 inches), Spread: 45-60 cm (18-23 inches). USDA zones: 4-9.

Achillea millefolium 'Strawberry Seduction' has orange-red flowers with a yellow centre and green fern-like foliage. The spread of 'Strawberry Seduction' is less aggressive than the species Yarrow. Full sun. Height: 45-50 cm (18-20 inches), Spread: 45-60 cm (18-23 inches). USDA zones: 4-9.

Achillea millefolium 'Colorado' is a strain that produces flowers in shades of red, pink, white and peach. This variety is inclined to spread, so you ought to site it carefully. Full sun. Height: 45-50 cm (18-20 inches), Spread: 45-60 cm (18-23 inches). USDA zones: 4-9.

Achillea millefolium 'Cerise Queen' has cherry-red flowers and green fern-like foliage. This variety is also inclined to spread so its growth will need to be curtailed each spring. Full sun. Height: 45-75 cm (18-29 inches), Spread: 60-75 cm (23-29 inches). USDA zones: 2-9.

Companion Plants

Yarrow looks great with a whole range of sun-loving perennials that bloom mid-summer. Mix them in with ornamental grasses, Veronica, Sedum, Echinacea, Daylilies, Shasta Daisies, Lychnis and Rudbeckia.

Pink and red yarrow mixed with other perennials. Private garden Uxbridge, Ontario.

Achillea millefolium 'Strawberry Seduction' and Veronica 'Eveline'

Achillea 'Moonshine' in the middle distance. Private garden Uxbridge, Ontario.

Achillea 'Moonshine'  with Veronica 'Eveline'. Private garden Uxbridge, Ontario.

 Soft pink yarrow mixes nicely with purple, white and orange flowers. 

Private garden Uxbridge, Ontario.

Plant Type: Perennial

Height: Depending on the variety, 12-29 inches (30-75 cm)

Spread: Depending on the variety, 14-29 inches (60-75 cm)

Flower: A range of colors including pink, cream, red, yellow, peach, terra cotta and maroon

Bloom period: Summer

Leaf: Soft, fern-like foliage

Light: Full sun

Divide: Early spring or fall

Problems: Aphids, powdery mildew, rust and stem rot

USDA Zones: Depending on variety from 2-9

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A Secret Garden: The Backyard Fairy Garden

In this, the final post in the series on Carole's garden, we will take a tour of the 

garden at the back of the house. 

There is no obvious fencing here. On the contrary, the forest surrounding backyard slips almost seamlessly into a cultivated space.

Gravel paths, like spokes on a wheel, lead you inside Carole's garden 

and to the raised pond that is at its heart.

 

One of the unique and distinctive features are the decorative frames which mark off the perimeters of the garden. Carole tells me that the frames were:

"... developed from a reprinted book offered by Lee Valley Tools called 'Beautifying the Home Grounds' that was originally published in 1926. We designed it together and my husband built it. I wanted something to define the edges of the garden and to add some winter structure as well. We started with the higher, larger section at the back as the focal point of the garden. As we came forward, we made the sections smaller with less segments."

Yarrow, Achillea 'Coronation Gold'



The decorative frames also serve as supports for climbers like this Clematis.

Clustered Bellflower, Campanula glomerata (Sorry, Carole wasn't sure of the particular cultivar, but says that this type of Campanula is well-behaved and is not an aggressive spreader.)

Dwarf Purple Bellflower, Campanula

Pink Yarrow, possibly Achillea 'Wonderful Wampee' which is part of the same Tutti Frutti series of Achillea as 'Pomegranate', which you can also see in if you scroll down just a bit further. 'Wonderful Wampee' has soft pink flowers and is a nice, compact plant. Full sun and somewhat poor soil with good drainage. Height: 45-70 cm (18-27 inches) 45-60 cm (18-23 inches). Hardy USDA Zones: 4-9.

Penstemon 'Dark Towers': Height: 60-90 cm, Spread: 45-60 cm. Full sun. Normal, sandy or clay soil are fine. Average to dry conditions. Zones: USDA 3-9

Feather Reed Grass, Calamagrostis x acutiflora 'Karl Foerster': is often overused in commercial settings, but is still a wonderful ornamental grass. Soft, feathery green plumes appear mid-summer and mature into wheat-like spikes.  Trim to the ground in early spring. Height:120-150 cm (45-60 inches), Spread: 60-70 cm ( 23-27 inches). USDA Zones: 3-9.

I asked Carole if there was any significance to the fairies in this part of her garden. She replied that there is "...no real signifigance, other than I like them."

Rose Campion, Lychnis coronaria: is a short lived perennial that re-seeds. The plant has a low mound of soft silver-grey foliage and magenta or white flowers. Full sun and average soil. Height 60-90 cm when in flower. Spread: 40-50 cm. The flowers have no fragrance, but butterflies like them.   Drought tolerant. Zones 3-9. 

Yarrow, Achillea 'Pomegranate': was bred to be a compact, bushy Yarrow. Full sun and somewhat poor soil with good drainage. Remove faded flowers to promote a second flush of blooms. Height: 45-70 cm (18-27 inches) 45-60 cm (18-23 inches). Hardy USDA Zones: 2-9.

Veronica 'Eveline': Height: 45-50 cm, Spread: 30-40 cm. Will tolerate part shade, but blooms much better in full sun. Normal, sandy or clay soil are fine. Moist soil is preferred, but it will tolerate average conditions. Deadhead to encourage repeat flowering. Zones: USDA 4-9

In the foreground on the right:

Euphorbia polychroma 'First Blush': has foliage that is green and white with pink variegation. Full sun and moist, well drained soil. Yellow flowers in spring. Height: 30-45 cm (12-18 inches), Spread: 45-60 cm (18-24 inches). Hardy: USDA Zones 4-9.

Monarda 'Petite Delight': I have this Monarda in my own garden, and despite its tendency to develop powdery mildew mid-summer, it is a really nice plant. Most Monarda are tall, whereas this one is short and compact. (Use this Monarda at the front of a flower border.) The flowers are a pretty shade of mauve. Unlike many taller varieties, which start to become a bit bedraggled as the flowers mature, the flowers on 'Petite Delight' always look attractive. 

Full sun with a bit of light shade in afternoon is ideal. 'Petite Delight' grows in a variety of soil types and likes average to moist conditions. When flowers fade and the foliage gets spotty, cut the plant back to promote fresh growth. Height: 25-30 cm (20-12 inches) Spread: 30-45 cm (12-18 inches). Hardy USDA Zones: 3-9

Yellow Verbascum with red Monarda and yellow Heliopsis daisies in the background.

Catmint, Nepeta x faassenii 'Six Hills Giant': Prefers sun and somewhat dry conditions with good drainage. Height: 90-120 cm (36-48 in), Spread: 60-90 cm (24-36 in) Cut the plant back 2/3 in July to promote fresh growth and more fowers. Hardy USDA zones 3-8.

I hope, with my photographs, I have managed to covey what a pleasure it was to 

spend a bright, summer afternoon in Carole's garden. 

Have a wonderful weekend!