Kahili ginger (Hedychium gardnerianum), a native of the Himalayas, is a gorgeous plant, which puts forth a generous display of fragrant, showy flowers. Too bad then that another description for the plant is ‘invasive weed.’ It thrives in moist areas – pretty much anywhere on the east side of the island. Its rhizomes form dense mats, and crowd out native seedlings, and birds eat the fruit and spread the seeds.
Controlling the spread of this plants requires its complete removal, but even then regular follow up is required as the plant can reestablish from dormant seeds or scraps of rhizomes left in the soil.
Graham's Island 
Its an invasive alien here in South Africa too. It is amazing how even small parts of rhizomes remain viable even when removed from the soil and left to dry out. We are continually removing these ginger plants around our place.
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Such a lovely flower, but it’s such a bad plant to have get a foothold.
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Yes it has a lovely flower, but can be bad in the wrong places as you say as it is so tenacious and displaces other lovely plants!
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