Paperwhite narcissus is a type of white scented daffodil which can be forced to flower for Christmas. A greenhouse makes it easier to grow better blooms. You need to buy specially prepared bulbs, and compost them afterwards because they rarely flower normally again. Store the bulbs in a cool, dry, dark, airy place until 4-6 weeks before you want them to bloom. Place them on a 5-centimetre (2”) layer of damp (not wet) bulb fibre or potting compost or even pebbles in a container such as a shallow bulb-pan. For small containers an odd-numbered group of (for example) three or five bulbs looks better than an even-numbered group. They should be close together but not touching each other or the sides of the container, with their pointy ends upwards and leaning in towards the middle of the container. Add a little more compost or pebbles to firm in between the bulbs but leave their tips exposed.
Place the container in a cool spot away from direct sunlight. Check them every couple of days to make sure they don’t dry out completely, but never add enough water to reach the bottoms of the bulbs or they will rot. As soon as the green shoots appear, move the containers to your greenhouse and give them as much light as possible. The more light and the less heat they get the less leggy and floppy the stems will be. Keep the greenhouse cool by ventilation but frost-free at nights, and make sure the plants don’t dry out. Turn them often to keep growth regular and upright. Bring them into the house when the buds are well formed, and the flowers will open in a few days.