Forcing Bulbs and Tubers

Two of the most important factors in forcing bulbs and tubers successfully are planning and timing. If you plant your bulbs too late, or leave them too long in a dark cupboard, they may flower too late or fail to flower at all.

With forcing, you can have spring-flowering bulbs blooming indoors in the depths of winter. Here we tell you everything you need to know to force bulbs successfully.

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You should purchase your bulbs in late summer, which is when they usually begin to appear on the market, although you can buy and plant them as late as October. However, the earlier you plant them the earlier they will bloom. Bulbs planted in late August should flower by mid-December.

When choosing your bulbs, look for those that have been specially prepared for forcing, to ensure that they will develop flowers at the right time.

Planting bulbs

  • Prepare a bowl by placing a thin layer of charcoal in the bottom and then adding a thin layer of bulb fibre which you have previously moistened.
  • Set your bulbs in the bowl, close together but not touching each other or the edge of the bowl. Finish by filling with fibre, but leaving some space for watering.
  • Place in a cool dark, well-ventilated cupboard or in a garage. The temperature should be no more than 4°C (40°F). Place folded newspaper on top.
  • When growth has started bring the bulbs out and gradually accustom them to the light by placing a cone of newspaper over them for a few days.

Equipment for planting

Buy any equipment you need at the same time as you buy your bulbs, so you do not have to delay planting because you do not have everything you need. For the planting medium you will need bulb fibre, or you can use a good soil-based potting compost mixed with equal parts peat. You will also need a little powdered or broken charcoal to keep the compost sweet, and a clean container without drainage holes.

 

Planting and growing

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If you are using bulb fibre, soak it first in some water and then squeeze it out so that it is just moist. Plant hyacinths, narcissi and daffodils with the ‘noses’ of the bulbs showing above the compost. Others should be covered with half their depth of compost.

Do not allow the compost to dry out; check every few weeks and, if necessary, moisten it a little. When the leaf tips are about 25-5cm (1-2in) high, bring the bulbs into a light but cool room at 10°C (50°F). When growth has reached 10cm (4in) increase the temperature to 18°C (65°F) and maintain this throughout the flowering period.

Bulbs to force

  • The following are single or double early flowering varieties: ‘Brilliant Star’, brilliant red; ‘Pink Beauty’, pink and white; ‘Diana’, white; and ‘Scarlet Cardinal, a double flowering scarlet.
  • Tulip (Tulipa)
  • Hyacinth (Hyacinthus) These are varieties of H. orientalis, known as Forcing bulbs and tubers
  • ‘Peeping Tom’ another N. cyclamineus hybrid with golden yellow flowers; and ‘Paperwhite’, a cultivar of N. tazetta, with fragrant white flowers.
  • Crocus: Of the many varieties of Crocus, the large-flowering Dutch crocuses are the most suitable for forcing: ‘Little Dorrit’, silvery blue; ‘Pickwick’, lilac with deeper lilac stripes; and ‘Kathleen Parlow’, with white flowers.
  • Dutch hyacinths: ‘Bismark’, pale blue; ‘Yellow Hammer’, cream; ‘Lady Derby’, pink; and ‘Princess Irene’, pink.
  • Daffodils (Narcissi) ‘Golden Harvest’, a golden yellow trumpet daffodil; ‘Jack Snipe’, a hybrid of N. cyclamineus with white petals and an orange-yellow cup;

Can I keep the bulbs in a cool place after they have flowered, and force them again the following autumn?

It is extremely rare for bulbs forced into flower one year to flower again the following year under the same growing conditions. Forced bulbs should either be discarded, or planted out in the garden.

Is it possible to force freesias to flower indoors in the same way as daffodils and hyacinths?

These are very tender and are not suitable for forcing, but you can grow them indoors to bloom at their normal time.

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