Gardening: Ready, Poinsett, grow...

Ah, Christmas time. Snowy walks, roaring fires, turkeys, puddings, tinsel-trimmed trees and, of course, a bright red Poinsettia on the table.

Over recent years, Poinsettias have become one of the must-haves at festive time, but do you give much thought to where they came from and how they are grown as you pick one up?

Our nursery at Pentland Plants near Loanhead produces more than 85,000 each year for supermarkets and other retail outlets, which sounds a lot, but across the world more than 500 million are sold. They originate from Mexico, growing as large trees and were discovered in the 1820s by American Joel Robert Poinsett, who took back some cuttings and grew them on.

We buy cuttings from Ethiopia and Kenya in July and propagate them on in little paper pots before transplanting into a one-litre pot once they are big enough. They can be tricky little blighters to grow and have very specific requirements – a warm cosy environment, no drafts, regular watering, low humidity, growth regulators to keep them compact, and feed to make them green and healthy.

We pinch out the main stem to make them branch out so they have lots of colourful bracts. The coloured parts you see are actually leaves and the little fuzzy yellow cyathia in the centre is the flower. We use biological control in our glasshouses to stay pest free and mix a special fungicide in with the compost to keep disease at bay.

If you give your Poinsettia the correct conditions it will reward you with colour for months, the one I had last year was lovely up till last week when I replaced it with a new one. If you would like to keep yours for next year you need to cut it back to about eight inches in March, re-pot it and care for and feed it like any other house plant.

Poinsettias are photoperiodic so they change colour as the day lengths shorten, so from mid-September to mid-October you have to keep your plant in total darkness when it becomes dark outside.

The more bracts a Poinsettia has, the better the plant, so choose yours carefully and keep them in your warm living room if you want to prolong their life past Hogmanay. Don’t worry, though, I’ll have another 85,000 for you to pick from next year!

• Carolyn Spray is director of Pentland Plants, Loanhead, www.pentlandplants.co.uk, 0131-440 0895, and a presenter on the BBC’s Beechgrove Garden.