What do gardeners look for in a perennial? What are the characteristics that make a perennial a “keeper?” There are many, including of course its beauty, whether it is invasive or not, whether it can support itself or needs to be staked, and the time and colour of the bloom period. One of the most important characteristics of a perennial that I look for is the length of bloom period. Some perennials are indeed beautiful, but in my relatively small garden it is hard to justify allotting them space if they bloom only for a couple of weeks every year; instead I try to choose plants which sport bloom for a much longer period.
One of the plant families with the longest bloom period is the Achillea plant family – more commonly called yarrow. These plants will begin to bloom in late June and will still have some colour in late fall when garden cleanup begins. They are phenomenal bloomers, and indeed, they are in bloom longer than any other perennial in my garden.
Yarrow is a tough plant – it is a native plant and you can find yarrow in the ditches throughout the Prairies. They never winterkill and although the native plants produce rather non-descript white blooms, the domestic versions have been bred to produce an array of colourful flowers including bright white, magenta, pink, coral, carmine red, mauve, and even a couple that are bicoloured.
Yarrow is an undemanding plant that will be happy in any ordinary garden soil. The plant is extremely drought tolerant – I have never seen mine wilt even in the hottest, driest period of the growing season. The foliage is attractive, being fern-like, and the plants generally get about 60 cm tall, although there are shorter varieties available as well. I never fertilize my yarrow and they still seem to thrive and they are planted in some of the driest locations in my garden where tree roots rob the soil of much of its moisture. Yarrow do like full sun, and a few of the plants that I have are forced to endure part shade and tend to get a bit floppy and require support, whereas if they were in full sun their stems would be stronger and they would be entirely self-supporting.
Like many perennials that have been developed from native species, the yarrow is not bothered by insect or disease problems. The blooms – which are really umbrels of blooms– last a long time but eventually some of them should be removed to improve the appearance of the plants and also to encourage the development of more bloom.
One of my favourite yarrows is my golden yarrow which produces bright sulphur-yellow blooms which hold their colour well whether on the plant or cut for use in dried arrangements. Some yarrows, however, are not as good at keeping their colour and tend to fade in the bright sun; the bicoloured Paprika is one example. In my garden I also have a pale-pink yarrow and a deep-burgundy one which both hold their colour well. There are some yellow yarrows whose blooms are a softer shade of yellow that blends into the border better than the golden one does; Moonbeam and Moonglow are a couple – they all seem to have the word “moon” in their names. I also like the bright-yellow Cloth of Gold yarrow whose umbrels have a felt-like texture (it is also the tallest yarrow). The foliage of this yarrow is blue green, while most yarrows have green foliage. The shorter woolly yarrow, which also has yellow blooms, has grey-green foliage, while the variety called Silver yarrow has silver foliage.
The one disadvantage of yarrow is that it tends to be invasive and some people are adverse to have such “spreaders” in their gardens. I find that yarrow is not that terribly invasive, it’s just that the clumps more than double in size during the growing season so each spring I simply – quite ruthlessly, as these are tough plants – remove over half of each clump to keep them in bounds. I do not recommend the variety that was developed a few years ago that flowers from seed in one year called Summer Pastels. Its blooms are often nondescript pale colours but worse yet, it self-seeds prolifically and becomes a weed in the garden. If you have some space in your perennial border, add a couple of yarrows and you will be delighted with their performance.
– Albert Parsons writes from Minnedosa, Manitoba