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Friday, June 22, 2012

Plant of the Month (June): Western Yarrow – Achillea millefolia

The garden is glorious with clouds of Yarrow blossoms this month.  Yarrow can bloom anytime from spring to fall in our area, but it reaches its peak in summer.   There are many good reasons to include Yarrow in a garden.  We hope this essay will convince you to try this easy-to-grow native perennial.

Yarrow grows throughout California (and western U.S.)  from the coast to the mountains.   You’ll find it in numerous plant communities from the coastal strand, coastal prairie and coastal sage scrub to the chaparral and coniferous forest.   In the wild it often grows in meadows and grasslands along with native grasses, perennial herbs and bulbs.   It often forms a natural groundcover between/beneath taller plants.

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 photo above).  The flower color is usually white, but there are pastel pink or purple variants which are the basis for several horticultural varieties (cultivars). 

We included the bright pink cultivar ‘Island Pink’ in Mother Nature’s Backyard to enhance our pinks/purples color scheme.  ‘Island Pink’,  a naturally pink variant from the northern Channel Islands, is available at many native plant nurseries (see page entitled ‘Where to Buy Native Plants’).   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.

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.  Despite its delicate appearance, Yarrow is one tough plant.  It can survive drought, seasonal flooding, alkali soils, sandy or clay soils, seaside conditions – even people walking on it.   Now that’s our kind of plant!

Yarrow is a natural groundcover.  It spreads via roots 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 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. 

Yarrow is an extremely adaptable garden perennial.  It can be grown in most soils and tolerates everything from full sun to part-shade.  You can even grow it in quite shady conditions, although it may not flower.  It is quite drought tolerant, though it  dies back to the ground under very dry conditions.  It will stay green from spring to fall with occasional water (Water Zone 2) or regular water (Zone 3). 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, water-wise groundcover once the larger plants mature.

Both the straight species and Yarrow cultivars are available at most native plant nurseries.  You can also grow Yarrow quite easily – and inexpensively – from seed.  Seed can be ordered on-line from both Larner Seed and the Theodore Payne Foundation (see ‘Where to Buy Native Plants’).    Store your seed packet in a plastic bag in the refrigerator for better germination.  We suggest starting your seed in containers (washed, recycled nursery pots or plastic drinking cups with a hole poked in the bottom work fine), then transplanting the plants into the garden.  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.  

We suggest planting the seeds in winter, when the rains can do some of the watering.  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 seedlings.  They will soon develop leaves that look more Yarrow-like.  In about 2 months they will be ready to transplant into the garden.

There are many reasons to consider including Yarrow in the home garden.  The flowers are lovely in the summer garden and make nice cut flowers.   Yarrow is one of the best native plants for attracting beneficial insects and repelling ‘undesirables’.   This is one reason that Yarrow was routinely planted – or left as a natural plant – around vegetable gardens 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.

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.  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 and the safe ways to use it.  This plant should be used sparingly, as allergies can develop.   

The entire plant can be used as a natural dye plant, producing shades of yellows and greens.   The flowers, foliage and seeds can be including in fragrant potpourri and sachets.  They are said to repel moths, houseflies and ants.  

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 to cut back old flowering heads and remove plants that have spread too far.  If you wish, you can deadhead (remove spent flowering heads) or mow several times during the summer.   Be sure to set your mower height to high – 4-6 inches – so you don’t damage the plants. After a short winter dormant period, plants will begin to grow again in the spring.  This is another good time to dig out unwanted plants.  You can re-pot these and give them away as gifts or use them as suggested above.

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