Why red hot pokers are ravishing
Coming in a range of sizes, kniphofias will withstand frost and give borders a blaze of late-season colour, says
ADMITTEDLY, i t has taken me half a lifetime t o appreciate t hem properly, but I now know there is so much more to kniphofias than the red hot pokers that give them their popular name.
Several years ago I started to plant them in my grass borders to add bolts of colour to what are otherwise quite subtle tapestries of hue and texture, especially as we now go into autumn. However, I wanted more than just a blaze so explored the possibilities that kniphofias had to offer, and I grew increasingly impressed by the range of colours and sizes available.
Kniphofias come from southern and central Africa, often from very damp situations, although our cooler climate means they will thrive with less water. Many are also very hardy as even in South Africa they will grow high in the mountains, where the temperature can drop to as low as -20C in winter. They are named after Johann Hieronymus Kniphof, an 18th-century professor of medicine and botanist from Erfurt in Germany.
Although we tend to use them as a lateseason blaze of colour in our borders, kniphofias can also be subtle, and some of my favourites – such as ‘Tawny King’, which has apricot flowers that last for an exceptionally long period, ‘Wrexham Buttercup’, which starts green and ages to a lime yellow, and ‘Little Maid’, which has small cream flowers – can almost look delicate in their flowering season.
Kniphofias have a reputation for being thuggish and dominant. One reason is that the most widely grown examples, such as K. rooperi and K.K uvaria ‘Nobilis’ ‘Nobilis’, celebrated for their vibrant poker heads, are the largest – ‘Nobilis’ rises as tall as 2.4m. Kniphofias are also often left undivided for too long and the clumps get too big. Most are better for being lifted and divided every three years or so, which not only stops them becoming unwieldy and overwhelming but also refreshes them and do does them a lot of good. When planting, it is a mistake to put them too deep, so always ensure the surface of the compost in the pot is flush with the surface of the soil in your border. They tend to be very adaptable and will grow in most soils, including heavy clay, although some need extra drainage and I put a handful of grit under the half dozen ‘Little Maid’ plants I added to my borders this spring.
While many red hot pokers start flowering in mid-summer there are a few types that wait right until the end of the season to brighten up a border. Of these, K. linearifolia is one of my favourites. It remains green throughout the summer but then in October the orange flowering stems appear for a brief few weeks of startling display. When it has finished flowering and died back it is a good idea to give the plant a thick mulch to protect it from the hardest frosts. The rather more common K. rooperi is another late kniphofia that will flower well into October, having started in September. Its flowers are more cone-shaped than upright and it’s rather hardier than K. linearifolia.
All kniphofias do best in full sun, although they will cope with some shade. They respond well to summer moisture but dislike sitting in cold, wet soil in winter. Mulching generously with garden compost in late autumn will help them through the worst of the winter weather. Many of them are evergreen but the fol i age of deciduous varieties should be left on the plant over winter. They often remain vibrant until March, when they start to die back and look ragged, and it will be time to cut back as new growth appears.