Coming down with yellow fever

At this time of the year our garden suffers a little from "yellow fever".

I do not mean the Head Gardener and I take weekends off and head over to Wellington to watch the Phoenix soccer team (although we do that occasionally) . No, what I mean is that yellow starts to dominate the flowers in the garden, with many brightly coloured perennials coming to the fore.

Primary among these are the delightful day lilies, Hemerocallis, one of the most popular of all perennials in the United States, yet somehow neglected in this country.

The common name and the Latin name refer to the flowers' ephemeral life span - literally here today gone tomorrow for these guys. Hemero is Greek for "one day", while "callis" means beautiful, so when the great plant classifier Carl Linnaeus was looking for an appropriate name for the genus in 1753 he hit on Hemerocallis.

Originally found in the wild in China, these plants have been hybridised for many years now and a wide range of plant forms and colours is available, although it has to be said yellow and orange shades still predominate.

Many gardeners have been familiar with the old thin-petalled yellow-flowered varieties and are rather surprised when they see more modern forms, with their deeper colours, stronger texture and much wider range of colours. We grow a number of yellow and reddish forms, as well as one lovely deep mahogany variety, which we planted in our dark-coloured border.

Day lilies are hardy and will cope with anything the weather will throw at them in Wairarapa - they bounce back from cold well and will cope with drought reasonably well too, although they do like the occasional drink during the heat of summer.

There are two different growth habits among modern day lilies - some go completely dormant in winter, the leaves dying off completely for the colder months, while others remain evergreen right through the year. I grow both forms and have to say the dormant forms are probably tidier in the garden as their dead leaves are removed as part of the usual autumn tidy-up, whereas some of the evergreen varieties mainly shed their dead leaves in the next spring, and you can end up with a plant covered in flowers, but also with dead and dying leaves in the middle of the clump.

Although day lilies will grow quite happily in most soil types, they do best in well fertilised, well-drained light-ish soil. We have some growing in quite stiff clay and, although they are growing all right, they do not compare to those growing in better soil. You can also grow these summer beauties in large containers, using a robust container mix. If you do not have any, you could make up a variety of the old John Innes mix - equal parts of good garden loam, peat moss (or composted bark) and well rotted animal manure.

Day lilies are true, long-lived perennials, with fibrous roots are varying from thin to fleshy and tuberous, extending from the crown, which is also where the leaves and flowers emerge. They are easy to divide and increase - just find where the fans are connected at the crown of the plant and carefully cut or pry them apart. You will find that some of the fans are not properly connected and you will only need to disentangle their roots. Try to be careful when undertaking division because even though snapping some of the roots is hard to prevent, it is important to keep as much of the roots as possible. If a fan snaps off of the crown without any roots you are doomed - the leaves will not grow new roots. These are vigorous plants, so when replanting make sure you leave enough room around them for their expansion.

There are many different varieties for sale in New Zealand, with lots of different nurseries growing their own ranges. One that many grow is the pretty little Stella Bella which has small golden bell-like flowers with reflexing petals on a tiny little plant - maybe a foot high. It looks just like that old favourite Stella D'Oro but is evergreen. It can even be used to create a low informal hedge and, in a warm spot, will flower for six months or so. Perhaps the best value of all the day lilies, especially for a smaller garden.

At the other end of the spectrum is the giant form, Spider Miracle. This has flower spikes well over a metre high with large numbers of flowers that are greenish yellow with thin petals that roll backwards in a slightly disconcerting manner, giving a distinctly spidery appearance. This variety flowers for months and is winter dormant.

Among the red-flowered forms, Oriental Ruby is as good as any, with good strong flowers that are ruby carmine red highlighted with an enchanting chartreuse throat. This is another long-flowering repeat flowerer that is also evergreen.

If lighter colours are your thing, Joan Senior could be just what you are looking for, with its near white blooms with a lime green throat. The flowers are large and are carried for months in repeat blooming. Evergreen.

We have a well-established plant of Midnight Magic in the back border, with its deep burgundy red flowers highlighted with a green throat contrasting nicely with the dark-foliaged manuka it is growing under. Like most day lilies, it will grow in this semi-shade but, to be honest, it would be much happier in the sun. This is also evergreen.

We do not grow any double varieties - they look a little messy to my eye - but Betty Wood and Moroccan Summer are two reliable varieties readily available - and both are golden.