(Editor's Note: This article was originally published on August 16, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
Kniphofias comprise about 70 or so species native to Africa. They are named after Johann Hieronymus Kniphof, a German physician and botanist.
The plants form clumps of long arching leaves and have an underground rhizome with fleshy roots. They like rich soil in an open sunny position and once planted resent disturbance. Spring planting gives them time to settle in before their first winter. They will tolerate a little frost, but are hardy only to zone 5 or 6 (as I found to my disappointment when I lived in Maine!) Practically disease free, they are tough plants and very easy to care for.
The plants look a little like Aloes with their fleshy leaves and tall stems covered with hanging flowers, but their leaves are not succulent like Aloes. The flowers are attractive to hummingbirds, insects and some other birds and are rich in nectar.
For gardeners the plants are indispensable additions to the late summer border and the bright colours light up a hot colour scheme. Years ago the red hot poker was an old-fashioned red and yellow flowering plant, but in recent years a lot of work has gone into producing hybrid plants that are now available in colours including creamy yellow, browny orange, coral and lime yellow. They make good cut flowers.
Two British gardeners who have championed the Kniphofia are Christopher Lloyd and Beth Chatto. The latter introduced the charming dwarf 'Little Maid', and Lloyd famously ripped out the rose garden at Great Dixter and replaced it with hot borders brimming with tropical looking dahlias, cannas and kniphofias.
Some varieties to look out for include 'Green Jade', 'Bressingham Comet', 'Toffee Nosed', 'Bees Lemon', 'Tetbury Torch' and 'Nancy's Red'. Plants are available in sizes ranging from 18 inches to towering 4 or 5 footers. Most garden centres carry them or you can buy them online.
Autumn colours like orange red and yellow are prized among tree and shrub growers, so why not incorporate them into your summer perennial border? Gardeners have often been shy to embrace the bold hot colours - orange must be the most misunderstood colour in the garden, but imagine acid yellow kniphofias paired with orange dahlias, shocking pink cosmos or dahlias with orange, or crocosmias and heleniums with accompanying yellow pokers. Blues and purples go well with kniphofia colours, providing a beautiful contrast. But if bold isn't your style you can still grow kniphofias, creams, greens and corals would fit into a calmer scheme.
I hope this article encourages you to try these wonderful perennials. I've loved them for years.
Photo credit Begoniacrazii for 'Green Jade'. Other photos of 'Timothy', 'Toffee Nosed' and the border at Howick Hall gardens are my own.