Seeing things grow (and grow well) in our gardens - where we can't help but think they do so despite our oversights or well-intentioned mistakes - is always a thrill and source of great pride.
But getting excited about a flourishing garden can often lull us into a false perception of how verdant our thumbs actually are. This is because some plants don't actually need us; they might act demure and delicate in their pots, but once they're in the ground, watch out!
I feel it is my duty to alert you to these wolves masquerading in designer sheep's clothing so, at the very least, if you still decide to grow them, you will know how much credit you deserve when they do well.
I'm not talking about plants like goutweed, ribbon grass, the so-called Jerusalem artichoke, Japanese knotweed or purple loosestrife, which are all considered terribly invasive. These plants have been on the gardener's radar for years and are well-known thugs.
Nor am I talking about plants that gracefully reproduce in the most convenient and natural way and, if necessary, are easy to edit out - yellow fumitory (Corydalis lutea), various types of self-seeding poppies, and even the dainty columbines (Aquilegia spp.) and lady's mantle (Alchemilla mollis).
Rather, I'm talking about attractive, seductive plants that haven't yet been roundly chastised for their pushy behaviour. One is the perennial Lysimachia ciliata 'Firecracker.' Known as Firecracker loosestrife, but unrelated to the wellknown purple loosestrife (which is actually a different genus, Lythrum), this striking perennial emerges with dark purple foliage that slowly shifts to suggest dark green and is decorated with complementary golden flowers. This plant received the Royal Horticultural Society's Award of Garden Merit in 1996, due I'm sure, to its sophisticated flower and foliage colour pairing.
But this plant has a root system that creates stolons or runners, much like mint, allowing it to travel widely and tenaciously. This means that by the end of its second season, one plant can create a colony that will muscle in on neighbouring plants and their root systems, requiring garden surgery to extricate one from another.
A relative of Firecracker is Lysimachia clethroides (gooseneck loosestrife), an elegant plant that, sorry to break it to you, will grow well for anyone, anywhere. With a similar galloping root structure, this perennial seduces many gardeners with its gracefully curving (hence, gooseneck) white blooms. It was also given the RHS Award of Garden Merit (1993) and was rather benignly described as "vigorous" and capable of forming an "extensive colony." It seduced me until it started to invade every other plant within six feet.
Now, this next plant is basically a mea culpa since it has been one that I have heartily recommended in the past. Anemone tomentosa 'Robustissima' (Grapeleaf anemone) is a late-summer-blooming perennial that offers up tall wands of pink flowers. It grows well in partial shade and puts on a reliable show from a young age. However, the folks at Fine Gardening magazine have it right when they say "it will overwhelm other plants and may become a nuisance in a bed." Drat. One of the reviews posted on their website says it all: "Robustissima might strike fear into the minds of many gardeners, who should take it at its word. If unable to resist its questionable worthiness, it would be prudent to rush out and buy a property of at least an acre in which to place this treasure - preferably in a far, rough corner."
Perennials with an architectural presence coupled with unique leaf colour and shape are always in demand by adventurous gardeners.
Many have been entranced by the plume poppy (Macleaya cordata), with its large lobed leaves with silver undersides and its statuesque form. However, of those initially smitten with this striking plant, most are smitten no more when their single plant becomes way too many by Season 2.
The moral here is don't be blindly seduced by interesting foliage or beautiful blooms. "Vigorous" usually means "needs strict management," so these plants are not for the laissez-faire gardener.
Ailsa Francis's blog can be found at hortus2.wordpress.com.