Hartley Magazine

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Forcing Christmas bulbs in the greenhouse

Now that the greenhouse is emptied of summer tomatoes, it’s the perfect moment to move in some bulbs. With a bit of luck and the wind behind you, you can have them in flower for Christmas, but if you don’t manage to hit Christmas just see them as a boon, something spring-like and jolly for the bleak early months of the year. Some rules: First, choose treated bulbs, from the garden centre or online. These will have been given the cold treatment required to fool them into thinking that they have been through winter already, and that now it is time for them to bloom, and if you buy non treated bulbs you will have to do this yourself, which is complicated. Potting up of forced bulbs doesn’t have to be as sensible as it does for most plants. You are putting them into short-term lodgings from which they are going to be turfed out as soon as they are past their best (ideally into the garden where they can live to bloom another day), so you don’t have to worry about the usual concern such as drainage holes, or frost-proofing. Any container that can hold water will do it: as long as you can hold the bulbs just above the well of water, you are away. And so for example you can pot them up in pretty ceramic bowls, or in the sort of hurricane lamps that double as straight sided glass vases. Pebbles, moss or bulb compost will do the job of keeping the bulbs lifted just above the well of water that your container will hold, so that they can just dip their roots down into it, rather than sitting directly in it and risking rotting. Hour-glass shaped glass bulb forcers are the ultimate expression of this, created especially to hold the bulb – usually a hyacinth in their case – just above the water, and designed so that the swirling roots become as much a part of the display as the flowers.

It is time to force bulbs for Christmas and beyond, and a spell in the greenhouse can help.

Hyacinths are the most urgent to get in if you are aiming for Christmas, and they should ideally be in by early October, though of course it is still worth doing them later. ‘Woodstock’ is a beautiful rich reddish purple, and ‘Carnegie’ a pure white. There is little point in comparing perfumes as all hyacinths are so strong and will scent the entire house, but both of these are good. They need to be kept somewhere dark and cool until they show 5cm of leaves. A shed is good, but you can also put them in a cool greenhouse here as long as you can exclude light, for instance by covering them with a cardboard box. After this time they need a week or so uncovered somewhere cool and bright, such as an unheated porch, or the cool greenhouse again. As soon as their leaves have greened up you can bring them indoors to flower.

Hippeastrums or Amaryllis should also be planted up from now on for Christmas, taking between six and eight weeks to flower. Pot them up into compost keeping half of their large bulb above the surface, water them, and keep them somewhere cool and bright until ready to flower. The same goes for paperwhite narcissi, which will do well in the brightness of the cool greenhouse as in low light conditions they can get leggy and floppy. Bring them in just as they are about to start flowering. Plant bowls of them staggered over the next few weeks so that you have a succession of them, and you are more likely to hit the date.