Diarmuid Gavin: Red carpet - the classic Poinsettia
A classic seasonal favourite, the Poinsettia can be nurtured at home with some very careful lighting
From giant succulents right the way through to the tiniest rock plants, euphorbias are a diverse and successful plant family. Many of you will be familiar with varieties such as Euphorbia characias Wulfenii, a handsome architectural plant with bold cylindrical heads of lime green flowers that sit proudly on silvery green leaves. This plant was greatly admired by horticulturist Gertrude Jekyll and is found widely in herbaceous borders today.
One of my personal favourites in this family is Euphorbia mellifera, the Honey Spurge, which forms a beautifully rounded shrub with elegant foliage and honey-scented flowers in spring.
But perhaps the most successful of this tribe is Euphorbia pulcherrima, otherwise known to Christmas shoppers as Poinsettia. This euphorbia is produced in its millions in preparation for the festive season and thousands of them are now lining the tills at DIY shops, supermarkets and garden centres and are purchased for indoor Christmas decorations and by last-minute shoppers as gifts.
In Ireland alone I know of one dedicated grower who produces hundreds of thousands of these winter favourites in a series of glasshouses in North County Dublin. It's not an easy task. Almost all will be grown for multiple retailers so standard sizes are a must. To achieve that is challenging: they have to be set on raised levels at exactly the right distance apart; the temperature has to be kept constant, with any breakdown of the heating system, the whole crop could be wiped out in a matter of hours.
The heat is required because the plants originate in Mexico. The shrub was first discovered by the American Ambassador to Mexico, Joseph Poinsett, after whom it is named. He was a keen amateur botanist and brought it back to the United States with him in 1828 - and the rest is history.
The cheerful red foliage has come to signify Christmas on both sides of the Atlantic. Legend has it that a poor young Mexican girl had no gifts to bring to the altar at Christmas so she gave what she could - some plants from the roadside which then miraculously sprouted red blooms.
The red blooms are actually leaves, called bracts, which are brightly coloured to attract pollinators. Breeders continue to work on new variations all the time and today they are also available in cream and pink versions.
There are very particular light and dark requirements to produce its brightly coloured bracts which growers now have down to a fine art. You need a certain amount of dedication to do this at home and that's why many people will discard the poinsettia after the festive season. The tricky bit is trying to get the foliage to colour up in time for Christmas.
The plant needs to be in complete darkness for 14 hours a day for at least eight weeks for the leaves to turn red. Start around next October to aim for red leaves for next Christmas. Use black polythene or somewhere that's completely dark for 14 hours and then, during the day, bring the plant back out to good daylight conditions.
Poinsettia comes from a dry, sunny country and will display signs of homesickness such as shedding its leaves if you don't make it feel at home. So, if you want to keep it happy, the first rule of thumb is don't expose it to any cold draughts. This includes the journey home from the garden centre or when bringing it as a gift. While they often come wrapped in plastic, I would cover the top with a plastic bag as well when transporting it.
Try to position it somewhere in the house that isn't susceptible to sudden draughts - hall doors and porches, for this reason, aren't the most suitable spots.
As a tropical plant it will enjoy good light but keep it away from direct sunlight. While it likes warmth, don't put it in front of direct heat such as radiators or fires. There's no need to sit your poinsettia in a tray of water, just water carefully when the soil is dry to the touch.
As with most indoor plants, the most common cause of plant failure is under- or over-watering so try to strike a balance. With modern breeding and a little care, you can be enjoying the festive foliage for many months to come.