Forcing Bulbs in the Winter

Posted by @jmorth on
Most daffodils are easy to force over winter. Let's discuss the best methods, and finish by giving some examples of some favorite cultivars from the various divisions.

Deep pots are best, allowing room for root development, but they need good drainage. 5 typical sized bulbs do well in a 6" pot. Bulbs may be placed in close proximity to each other, but preferably not touching. Press firmly into the medium; more medium used to cover 'shoulders' of bulbs. This too should be firmed in.

When thinking about forcing bulbs for the winter, you have two options. The first is placing your pots outdoors, plunged into the earth and covered with a protective layer of insulation (light soil, leached ash, straw, or pine needles). The protective layer must be a substance through which emerging buds (shoots) may grow through unobstructed. Using this method, you will have to maintain watering, but not too much. Usually 12 weeks is sufficient outside, at which time you will bring the potted bulbs inside. Water more frequently at this stage, never allowing the soil medium to become dry. Also, the higher the humidity you can create, the better. If you wish to keep using your forced bulbs for several years, flowering stems are removed, weak tomato (high potash) fertilizer may be applied, keep in bright light till warm enough to translocate, then plant bulbs outside in the spring. They will often bloom the following season, although they sometimes need a season to recover.

The second option is to pot up the bulbs as described above in the fall. Let the roots get a good start by watering and letting them sit for a week or so before placing into a dedicated refrigerator with the temperature maintained at around 34 to 40°. Check water periodically. 12 weeks later, or when obvious growth is noticed, pots will be well rooted and may be removed. I let mine acclimate under fluorescent lights in the basement where winter temps average around 60° for a week or so. It is during this time that the flower stalks will emerge. When the buds are about to burst, move them to their desired location for display. To enjoy in subsequent seasons, as described above, transplant into garden.

Before having a refrigerator dedicated to forcing, I was able to successfully force bulbs by utilizing a covered outside stairwell that led to the basement. Bulbs were potted up and placed in big totes. The totes were then placed in the stairwell and covered with blankets. This method's advantage was less watering because the humidity was maintained by the enclosure.

Cold stage of forcing (2 methods I use)

Refrigerator dedicated to forcing:
Thumb of 2013-08-30/jmorth/24adad

Tote in a basement's covered stairwell (overflow area).
Thumb of 2013-08-30/jmorth/15d8e9

After the cold stage, pots are put under fluorescent lights in basement where the temperature is around 60°. When buds are fully formed, the pots are moved upstairs (higher temps) to enjoy.

Thumb of 2013-08-30/jmorth/6cb803

Daffodils are classified in 12 divisions. Some divisions are more forcible than others. Below are the recommended cultivars, grouped by division, that I’ve personally had success forcing:

Div. 1 Trumpet Daffodils:

Trumpet Daffodil (Narcissus 'Topolino')
Trumpet Daffodil (Narcissus 'Mount Hood')

Div. 2 Large Cup Daffodils:
Large-cupped Daffodil (Narcissus 'Carlton')
Large-Cupped Daffodil (Narcissus 'Delibes')
Large-Cupped Daffodil (Narcissus 'Ice Follies')
Large Cup Daffodil (Narcissus 'Smiling Sun')
Large Cup Daffodil (Narcissus 'Sound')

Div. 3 Small Cup Daffodils
Small-Cupped Daffodil (Narcissus 'Barrett Browning')

Div. 5 Triandrus
Triandrus Daffodil (Narcissus 'Ice Wings')
Daffodil (Narcissus 'Petral')
Triandrus Daffodil (Narcissus 'Thalia')
Triandrus Daffodil (Narcissus 'Hawera')

Div. 6 Cyclamineus:
Cyclamineus Daffodil (Narcissus 'Itzim')
Cyclamineus Narcissus (Narcissus 'Jack Snipe')
Cyclamineus Daffodil (Narcissus 'Jetfire')
Cyclamineus Daffodil (Narcissus 'Rapture')
Daffodil (Narcissus 'Tete-a-Tete')
Cyclamineus Daffodil (Narcissus 'Emcys')

Div. 7 Jonquilla:
Jonquilla Daffodil (Narcissus 'Curlew')
Jonquilla Daffodil (Narcissus 'Derringer')
Jonquilla Daffodil (Narcissus 'Hillstar')

Div. 8 Tazetta (need little or no cold time to force):
Tazetta Daffodil (Narcissus 'Falconet')
Tazetta Daffodil (Narcissus 'Martinette')
Paperwhites

 



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