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Invasive Garden Plants

Diana was a member of the Royal Horticultural Society. She & her family all love gardening. She enjoys photographing & painting plants too.

Plants Which Are Attractive but Spread Rampantly to Take Over Your Garden

I first came across the phenomenon of invasive plants many years ago when I inherited a garden which had very little in it except snow-in-summer and grass in the back garden, and heuchera (London pride), a dog rose and grass in the front garden.

All attractive plants, thought I, but the garden looked a little empty and needed more variety.

In the end, I had to dig out all the snow-in-summer, as it spread all over my rockery. I left the rose bush to flourish as I couldn't bear to cut it down, and I wish I hadn't cut the heuchera back so vigorously, as it barely recovered and was not in fact at all invasive.

Heuchera (London Pride) Is a Very Hardy Perennial But NOT Invasive

A Word of Advice:

Of course, it's important to remember that just because you have invasive plants--rampant growers--it doesn't mean that you need to ban them from your garden design. Just keep an eye on them, and control them, cutting back, uprooting, clipping, and whatever is appropriate to stop them taking over. Many invasive plants are very beautiful, but you need to let them know that you're the master.

Amazingly, Sixty Years After I Took Over My Garden, I Still Have the Same Heuchera I Described in My Introduction Above

I discovered that these particular plants were not in fact invasive, but just vigorous growers in the right conditions, and they certainly have strength and fortitude.

When I started, I bought a few rockery plants over the next year or two, and the rockery looked quite appealing. The white flowers of snow-in-summer bloomed from about April to June, and the small fluffy textured silver-grey leaves were the perfect foil, even if the whole lot did look a bit straggly in summer. Gradually the innocuous-looking plants carpeted the whole rockery and the other rockery plants were subsumed and, one by one, disappeared. I was reluctant to cut them back because they were so beautiful. I would pull out bits here and there, and leave the rest. But in the end I dug the whole lot out...and then I was sorry.

1. Snow-in-Summer

Snow-in-Summer (Cerastium) is Also Known as Mouse-Ear Chickweed, or Silver Carpet--Above is a Close-up Showing the Dainty White Flowers and Silvery Grey Leaves

This is a perennial which tolerates drought and will grow in dry to moist soils. It prefers well-drained, loamy or sandy soil and requires full sun. Snow-in-summer is grown as ground cover with a height of 6-8" (15-20 cm.).It bears masses of small white flowers which bloom in early summer, May and June, above the dense mat of silvery grey foliage.

Trim plant back after flowering to keep it neat and compact.

2. Montbretia - Biological Name Crocosmia

Montbretia (Crocosmia)

Montbretia (Crocosmia)

The Flowers of Montbretia Grow in Delicate Racemes of Rich Golden Orange or Flame Colour

These are deciduous perennials which flower on an arched spike from early summer until autumn. This long-flowering season and satisfying flame colours makes them good value in my eyes, regardless of their bad behaviour. The long leaves are very attractive in spring, but after flowering they flatten and die back and can make the flower border look a bit of a mess if not cut back. They grow from basal underground corms . The corms are unusual in forming vertical chains with the youngest at the top and oldest and largest buried most deeply in the soil. The roots of the lowermost corm in a chain are contractile roots and drag the corm deeper into the ground where conditions allow. The chains of corms are easily separated, which enables them to become invasive and difficult to control in the garden.

Although they are natives of South Africa, crocosmia are still winter-hardy in more temperate regions and flourish in full sun or partial shade

They are easy to propagate by division, removing offsets from the corm in spring: each corm will grow into a separate plant and they need to be planted in clumps.

They grow to about 1 - 2 ft high but may grow up to 1-5 ft. (30-150 cm)

3. Euphorbia

There Are Many Varieties of Euphorbia, Some Invasive Growers, Some Not so Rampant

The buds start showing above ground in early spring, and gradually unfurl to show delicate yellowy green flowers with slightly darker yellow-green leaves which last through spring, summer and autumn--is that good value or what?. These perennials spread slowly, over a number of years, so you may not immediately notice the take-over. Just keep them under control, grubbing out the surplus, and you will have valuable plants, about 8 - 12 inches (20-30 cm.) high which are very attractive and because of their modest colouring, they are a good foil to other plants.

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4. Periwinkle - Vinca Minor

Periwinkle With Small Flowers is Called Vinca Minor, and the Larger Variety is Called Vinca Major

Evergreen low-growing perennials which flourish in sun or shade, even under trees, so they are particularly good ground-cover. They have appealing mauve flowers in spring, and then sporadically throughout summer and autumn. In drought conditions be sure to water them. They spread by a network of small roots which grow out of the stems as they creep along the ground. They are about 3 - 6 inches (7.5 - 15 cm.) high.

Take care, because they are very invasive if they like their position, and win any battle where they are in competition with other plants. They are so lovely, with their shiny dark green leaves and little flowers winking at you, that I always feel reluctant to dig them out and cut them back, but you don't want a whole garden with nothing but periwinkle in it, do you?

Just be strict, make a decision where you want them, and don't let them spread beyond that.

5. Weigelia

Weigelia Is a Large Shrub

Weigelia is a deciduous shrub reaching about 10 ft (3 m.) in height. It flowers for a short time in spring and then does nothing much for the rest of the year except that it looks quite pleasant and green.

I grew one plant at the back of my garden, and it spread so much that it now occupies an area of about 50 square feet in the golf course just beyond my back garden, and still spreading, so I cut it back every year. But still worth keeping.

6. Anemone Japonica

Anemone Japonica

Anemone Japonica

Anemone Japonica--One of my Favourite Flowers With Shapely Beautiful Leaves and Delicate Pink or White Flowers in Autumn

Anemone Japonica, Height up to 4ft (1.2m.), always looks good--the new leaves start to develop in mid Spring and grow into a crescendo of large ornamental leaves and heads of flowers in late summer. When they die back, the woody flower stems can be cut and removed, leaving the leaves which remain ornamental. They spread by strong underground roots and you need to make sure you have dug out completely the bits you don't want, as it doesn't take much to get them spreading again. But keep them under control and you have a magnificent perennial with a long flowering season.

7. Forget-me-Nots (Myosotis)

Forget-me-Nots Are Rampant Self-Seeders but Easy to Clear

They are useful plants because they flower from late March to late May, giving a marvellous blue and pink display of delicate blooms. They self-seed vigorously and for this reason, some gardeners call them weeds, and pull them all out. Personally I love them, and only pull out the flowered plants once they have partially seeded, so that there will be a good display the following year, knowing that they are easy to control because they have short roots and I need only keep as many or few as I want. They grow to a height of 6 - 23 ins.(15 - 60 cm.).

8. Borage

Borage--Another Beautiful but Invasive Plant Which Seeds Itself Copiously

They flower from early summer through to Autumn and the blue flowers are very attractive. Borage is actually a herb, and as it is beloved by bees, is sometimes grown as a companion plant to vegetables which need pollinating.

They are annuals, and self-seed prolifically, so are inclined to take over large areas of garden beds, but are easy to control by pulling them out when they are still young, before the roots have taken hold. They grow to a height of 1 - 3 ft. (30-91 cm.).

9. Wild Geranium

Wild Geraniums are so Beautiful That It's Tempting to Leave Them to Flower

They start to bloom in late May for a couple of months. When they finish blooming, if they are cut back they will flower vigorously again in late summer and early autumn. They do tend to spread like mad, hiding any smaller plants, and gradually swamping large areas. Cutting them back rigorously gets them to bloom again, but, in order to stop them spreading where you don't want them, you do need to dig out the roots as well as just cutting back the very pretty leaves. They grow to a height of 1.5 to 2 ft. (30 - 60 cm.).

RHS Encyclopedia of Plants and Flowers

Take the Poll Below About Invasive Garden Plants--See How You Compare With Other Voters

Invasive garden plants can be hard work to control.

But would you really want to dig them out completely, if they bear beautiful flowers, like borage and forget-me-nots in the pictures above?

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