How to force spring bulbs for winter colour

The window of opportunity for planting bulbs to flower for Christmas may be closing, but there’s still time to bring spring colour forward into winter. Plant your bulbs between mid-September and the end of November and they’ll produce beautiful displays that will inject colour and fragrance into your home during the cold, dark days of December, January and February. Read our top tips on how to force bulbs and then browse our bulb pages for more inspiration!

What does ‘forcing’ bulbs mean?

When we force bulbs, we treat them to conditions that mimic their natural dormancy period. This normally means subjecting them to a period of cold and darkness.

This artificial winter is achieved by placing the potted bulbs in total darkness between 1.5- 10℃ for several weeks – a dark, frost-free shed, garage or basement is ideal. During this time the bulbs are fooled into thinking that it is winter and will be stimulated into developing a good root system before pushing out a shoot. After this period, the pots are brought into the house and treated to conditions that mimic the spring. A warmer but still cool position, around 15℃, in bright, indirect light is recommended.

There are a few exceptions to this method. Some species, such as Amaryllis, do not require any pre-chilling, whilst neither Crocus or daffodils (Narcissus) require darkness.

Bulbs treated in this way will flower much earlier than they would naturally, so you can enjoy the scent and colour of spring bulbs throughout December, January and February.

What are the best bulbs to force?

Hyacinths and Paperwhite Narcissi are popular plants to force in time for Christmas, but it is possible to force a wide variety of hardy spring bulbs to enjoy indoors during winter. Here are a few of our favourites:

• Anemone blanda

• Hyacinth

• Muscari

• Iris reticulata

• Narcissus – ‘February Gold’ or ‘Snow Baby’

• Crocus

How long does it take to force bulbs for winter flowering?

The total length of time between potting up your bulbs and blooming can be anything from 6-18 weeks. Exact timings vary according to variety, the size and quality of the bulbs, the temperature that you give them during their chilling period and the temperature and light levels when you bring them into the house.

When should I plant my bulbs for forcing?

Plant your bulbs between mid-September and mid-November to force them to flower in late winter.

Most bulbs require somewhere between 6-15 weeks of cold treatment. After you have brought your bulbs into the house, it can take another 2-5 weeks for them to bloom.

Getting bulbs to flower at a specific time, say Christmas week, requires a combination of experimentation and experience. Planting several pots over several weeks between September and November gives you the best chance of success.

When your bulbs are ready to be removed from their cold, dark spot and are brought indoors, it is still possible to manipulate blooming time. Bulbs that are growing too quickly can be placed in a colder spot to hold them back, whilst any that are still small can be given a slightly warmer position. Always avoid placing your bulbs in a very warm spot, as this will stretch the stems which will then fall over when they carry the blooms.

If you are forcing Hyacinth bulbs it is a good idea to plant each bulb into a separate pot. This is because some bulbs will grow faster than others. When the chilled bulbs are ready for moving into the house you can select several of the same size and pot them up into one container. This way they should all flower roughly at the same time.

The table below gives rough guidelines for how long it takes forced bulbs to bloom. Count backwards to work out the time of planting.

When do you plant bulbs to bloom in time for Christmas?

Imagine inhaling the sweet fragrance of a bowl of deep indigo Hyacinth ‘Dark Dimension’ or the heavenly perfume of exquisite Narcissus ‘Paper White’ (Narcissus papyraceus) on Christmas day! A container of Christmas flowering bulbs that you have prepared yourself also makes a fabulous festive gift with a personal touch.

Hyacinths and Paper White Daffodils will require around 12-14 weeks in total from planting to blooming, so planting must be completed by mid to late September.

Amaryllis require no pre-chilling and take approximately 6-10 weeks to bloom. Plant them by early to mid-November for Christmas blooms.

What should I do if I am too late to force bulbs for Christmas/New Year blooming?

Buy ‘Prepared’ bulbs instead. These have been specially temperature-treated to enable them to flower around Christmas and New Year.

Potted pre-prepared bulbs given as Christmas presents are already in bud and should flower a couple of weeks after receipt. Narcissus ‘Paperwhite’ makes an exquisite festive gift. These pre-shooted bulbs promise up to 10, snow-white flowers that will fill the home with a heavenly fragrance for weeks. For something bigger and bolder, try the trumpet-blooms of Amaryllis. These show offs are fabulous as a table centrepiece. Browse our Christmas Gifts section for more inspiration.

How do you force prepared hyacinth bulbs?

Prepared hyacinth bulbs have been temperature treated to force them to flower sooner. Plant them in containers and place in a cool, dark spot for 6 weeks. Hyacinths that have not been treated may also be forced, but they will need about 10+ weeks in a cool, dark place.

When the shoots are around 7.5cm (3”) tall gradually increase both light and temperature. Place the container somewhere cool and shady for a week to allow the leaves to become green and begin to open to reveal the flower, before moving the container to brighter light in a warmer location.

Removing spring bulbs from their artificial winter too early will mean that they do not grow sufficient roots and will not be able to push out the flower bud.

Step-by-step guide to forcing indoor bulbs

1. Select bulbs that are firm and large – the bigger the bulb, the bigger the bloom. Avoid any that are soft, show signs of disease, or have damaged outer layers.
2. Choose a container – it’s all part of the display. I grow indoor bulbs in dishes, glass cube vases, terracotta bowls, lined baskets, and wooden seed trays. If the container has no drainage holes, use bulb fibre. If there are drainage holes, use a loam-based medium mixed with grit – I sometimes use the grit as a decorative mulch as well.
3. Plant bulbs with their growing tips just nosing through the compost. Make sure that they’re close together, but not quite touching. Hyacinth bulbs can cause itchy reactions in some people, so do wear gloves when handling them.
4. Water them in, then place them somewhere cool, and, if the bulbs require it, dark. Check them regularly and water only if necessary – while they don’t want to be sitting in water, they must not dry out.
5. When good roots have developed and short shoots have pushed through to around 4-5cm long, the pots can be moved indoors. Place them in bright, indirect light away from draughts and radiators.
6. Check your bulbs regularly and rotate their containers if plants lean towards the light. When they are brought into the warmth, they will also require more water. If they dry out at this stage, unopened flower buds may fail to develop.
7. When siting containers, consider the bulbs’ requirements. Iris reticulata will last longer if they’re in a cool room. Daffodils need more light than hyacinths, so place them in a sunny position to prevent them becoming too tall.
8. After flowering, cut off the old flower heads and allow the leaves to die down naturally. You can replant hardy bulbs outside when the soil is workable. Narcissus ‘Paperwhite’ are not hardy, so either dry them and replant in early autumn, or leave them in their containers.

In addition to those in decorative containers, I grow some bulbs in plastic plant pots as they allow me to select those that look as if they’ll come into flower at the same time, so that I can arrange them together in containers for the house. If too many bulbs are ready at once, hold some back by keeping them cool for a while longer.

Awaken your senses from winter hibernation with an early display of colourful spring bulbs. Indoor bulbs present a wonderful opportunity to be creative. From a simple and beautiful bowl brimming with Iris reticulata, to a miniature table top landscape of colourful flowers mingling with decorative twigs and cones, spring bulbs can be used to create varied and uplifting indoor winter displays.