The Casual Gardener: Heleniums help keep a sense of summer well into September

If you're hoping to extend your late summer display by a few weeks look no further than the beguiling helenium

Many heleniums have ‘rhubarb and custard’ colour combinations

WHEREAS summer often peters out, leaving a blurred line between the seasons, this year autumn appears to have arrived quite suddenly.

We may yet be treated to a period of bright, stable weather that can be characterised as an Indian summer but there's no doubt that the hot, sweaty days are well behind us. Soon the leaves will drain of chlorophyl, triggering an autumn display of red, yellow and orange foliage – watch this space to find out where you'll get the best colour over the coming weeks.

As the nights become noticeably longer and the temperatures fall, gardeners do their utmost to keep the spirit of summer alive. Sheltered areas will fare best, while dead-heading will prolong a plant's flowering period.

For me, perennials in the asteraceae family are those which best evoke a sense of summer well into September. Varieties of aster, coupled with Rudbeckia and Echinacea are classic prairie plants that will stay upright and in bloom for a few weeks yet, as long as they are not battered by heavy rain or blustery winds.

The helenium is another North American plant with a daisy-type flower that extends seasonal interest. Their distinctive shuttlecock flowers have velvety petals, many with vivid ‘rhubarb and custard' combinations in shades of spicy red, hot orange, caramel, yellow and rust, while at the centre is a soft, bonbon-like ball of various colours.

Following the example of the bees that lap up the helenium's pollen, there's almost a temptation to eat what looks like the seductive, sweet centre; however, it's worth noting that this plant is poisonous to most mammals. It has been used medicinally, though, and is known commonly in the US as ‘sneezeweed', because helenium's petals were used for making snuff.

The best time to plant these herbaceous perennials into a fertile, well-drained border is in spring, when they'll also tolerate division. As long as conditions are right – ie they get plenty of light and adequate water – then they'll not require much attention.

They are a plant said to respond to the ‘Chelsea chop', which sees around a third of growth cut back relatively early in the season – at the time of the eponymous flower show – thus encouraging studier growth and a greater profusion of flowers.

Some maintain that heleniums will work in both a formal and naturalised setting but I'm a bit sceptical about the former. When you consider its best companions are Verbena bonariensis, late-flowering ornamental grasses, bronze fennel and all the above mentioned prairie plants, it has to be informality writ large or else something more rigid in form but very bold.

There is an abundance of varieties available. The German nurseryman and horticultural visionary Karl Foerster, who gave his name to a great reed grass cultivar, also bred heleniums, giving the world ‘Flammenrad' (meaning ‘flaming wheel') in the early 1950s. It is a tallish, sturdy variety with flowers that are brown in the centre with predominantly yellow petals flashed with red.

'Moerheim Beauty' is slightly taller, at more than a metre, with red petals that face downwards. With taller varieties, especially those that haven't had the Chelsea chop, some staking is often necessary to prevent them toppling. Taller types also have rather ugly stalks which necessitates the screening of the stalks with other plants.

Alternatively select a shorter variety that needs no support, such as 'Kleiner Fuchs', with two-tone flowers of deep red and gold. The dwarf and bushy 'Rubinzwerg' has ruby-red flowers and the RHS's Award of Garden Merit.

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