Saturday, July 11, 2009

Yarrow, Her Sunshine Plays Upon Thee

Achillea, commonly called Yarrow, is a perennial herb in the Asteraceae family native to parts of Europe, Asia and North America.

It produces flat flower clusters, 2" to 6” across which may include hues of red, pink, gold, yellow and white. Flowering begins in the spring and continues well into summer or even fall. Flower stems range from 12" to 36" in height. The 3” to 8” feathery, fern-like leaves are green or gray and have a fresh, spicy fragrance.

Yarrow, also called ‘Nosebleed Weed’ for its ability to stop a nosebleed, is an immuno-stimulant. It has been used to prevent cold and flu and lower blood pressure, promote digestion and relieve headache, earache and tooth pain. But, as with many medicinal herbs, there are dangers associated with ingesting it.

Yarrow is most widely grown for its ornamental qualities. It lends drama to the perennial border and is excellent for cutting and drying.

If grown in USDA climate zones 3 - 9, Yarrow takes care of itself, requiring virtually no attention. Some cultivars will tolerate heat in Zone 10, but need extra care. Otherwise, it thrives in full sun and in poor, gravely and infertile soil conditions. They can live with a minimum of 8” of rain per year, so they're excellent for xeriscaping. Though drought tolerant, Achillea should be watered during extended dry spells.

Yarrow can be started from seeds or seedlings, but they may lack vigor and be finicky about water and weeding. Let someone else deal with the stress and buy them as bare root plants or growing in small containers.

The Achillea root system needs a minimum of 8” of soil. If your landscape only has a thin layer of topsoil, raised beds or terracotta pots should provide enough depth. Achillea needs a pH between 6 and 8.

Prepare a planting bed by cultivating at least 6" deep, removing all traces of weeds. Add enough soil to raise the bed at least 4" above the surrounding ground level. This will help to promote good drainage. Next, incorporate compost or 5-10-15 fertilizer at the rate of 2 lbs. per 100 square feet into the top 4" to 6" of soil. Do not allow synthetic fertilizer to come into contact with the plant.

Plant Yarrow 12" to 24" apart. Dig planting holes into the cultivated soil a little less deep than the depth of the growing container. Place the plants into the holes and back-fill, watering as you go. Press soil around the root balls. Do not cover the root balls with soil. The tops of the root balls should be slightly exposed. Add a top-dressing of mulch around the plants, not on top of them, about 1" deep.

Achillea spreads by underground rhizomes, so after 4 or 5 years you might thin your plants in the spring. If left to themselves, they will most likely out-compete less aggressive plants. After digging around the perimeter of the mature plant, lift it up and shake off excess soil. Divide the clumps along their natural divisions and replant. Water frequently until you see new growth.

Darker colored flowers may fade in temperatures higher than 80ºF or as they age. You can deadhead flowers to extend the blooming season, but that won’t last past mid October. Or leave the spent flowers on for the birds to enjoy in the winter. In winter the leaves will fall off and may be removed. The evergreen crowns may remain.

Because some Achillea can grow 3' tall, it is best to plant those behind shorter ones, obviously. They can be easily staked, but it may not be necessary. I’ve seen them staked, or leaning over naturally at an angle as if they wanted to greet my knees while I walked along the garden path.

Achillea is susceptible to a preventable disease: mildew. Plants in humid climates, poor sunshine or soggy soil will most likely catch this grey spotty fungus. If your plant has new signs of mildew, spray it with sulfur when the plant is moist with morning dew. Plants with advanced mildew should be removed.

Yarrow is perfect for borders or in mass plantings. It is self-sowing and will spread indefinitely even on slopes. Infrequent foot traffic is tolerated. For an attraction to butterflies that is deer and rabbit resistant, one can’t go wrong with this plant.

Achillea is visually appealing in fresh or dried arrangements. If you want to dry them, cut them at their peak before they fade and hang them upside down in a dark place to avoid the sun’s bleaching rays. They retain their scent and are fragrant in potpourri. The flat flower heads are a great contrast to other shapes.

Horticulturalists have hybridized beautiful cultivars you’ll want to nurture. Among the many cultivars are these beauties:

A. filipendulina ‘Coronation Gold’ - Bright yellow clusters that grow up to 42” high and spread up to 2’ in Zones 3-9.

A. millefolium 'Cerise Queen' - Vivid pink flowerheads that grow 18” high in Zones 3-9.

A. millefolium 'Fire King' - Bright crimson petals surround a yellow center. It grows in Zone 3 - 8 up to 2’ tall.
A. millefolium 'Lilac Beauty' - A taller Achillea that grows 3’ tall in Zones 3-10 with lavender blooms butterflies love.

A. millefolium ‘Oertel’s Rose’ - Pink to light red 2"- 3” clusters that grow about 24" tall. Spreads at least 18”. Successful in Zones 3-10.

A. millefolium 'Paprika' - Orange-red flowers provide a riot of color from Zones 4-8. Has 3” blooms. Height and spread of 2’.

A. x ‘Moonshine’ - This canary colored flower blooms from June to September in Zones 3-9. Has bigger blooms up to 4”. Height and spread of 2’.

Many cultivars exist from crossing and back-crossing among Achillea species. If you’ve been looking for a friendly, low maintenance perennial flower that is drought tolerant, cold-hardy, heat-resistant, deer resistant and produces a specific color for your garden, look no further.

Return to Achillea at goGardenNow.com.

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