Introduce Crocosmia into
your garden, either by planting it's button-like corms or an established plant, and within 2 or 3 years you will be digging up portions of it to plant elsewhere in your garden or to give away to other gardeners.  It makes itself right at home and multiplies quite freely underground.

 

Not exactly what I would call invasive (though some might), it is simply strong willed.  As nothing seems to bother it, it is virtually trouble-free.
The variety 'Lucifer' is a fiery red that always catches the eye of visitors.  My garden also has a bold, golden yellow variety named 'Jenny Bloom.'
There are also orange varieties.

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