Forcing bulbs has been a gardening hobby for centuries. Medieval tapestries and ancient frescoes depict forced bulbs blooming, sometimes in special crockery or glass vases. Blooming hyacinth in special hyacinth glasses became the vogue during Victorian times, and the pastime’s popularity continues today.
You can enjoy the fragrance of attractive and colorful hyacinths all winter long if you force them properly into bloom.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Amaryllis is a popular indoor bulb planting that’s often forced into bloom around the holiday season.
Photo Credit: ©2002 Dolezal Publishing/Donna Krischan
Spring bulbs are the most commonly forced plants; only a few summer and evergreen bulbs are forced into bloom, usually so their flowering matches specific holiday occasions. You can force bulbs for display indoors in your home while outdoor conditions are still too cold to permit their growth, and you can force bulbs in your garden beds to match a special occasion like a wedding or garden party. The general process is easy to master. Achieving blooms for a specific time just requires planning and some experimentation.
Forced spring and summer bulbs – crocus, daffodil, hyacinth, flag iris, Easter lily, paper whites and tulip, among others – are cured and stored depending on the species until 4-10 weeks before they are to be planted. Then they’re chilled by keeping the unplanted bulbs in mildly humid conditions at 35-45 degrees F. Following the chilling, they’re planted in soil or suspended over water, then held in a low-light area at 50-65 degrees F until they develop abundant roots and green shoots. Finally, they’re brought inside into a bright display location at 65 degrees F during the day and 55 degrees F at night, where they quickly grow foliage, develop flower shoots and bloom. The total time needed is 12-20 weeks from the beginning chill period until flowers.
You can force your bulbs in water for an attractive, one-time display, or you can plant them in soil in containers (or even in the garden, weather permitting).
Since bulbs are reared throughout the world before your garden retailer receives them, you might be planting some bulbs grown in a different hemisphere with seasons reversed from those in your region. Other bulbs have been prechilled, heat-treated or held under controlled conditions for varying, precise lengths of time, making them variable in their growth and bloom times.
For this reason it’s best to set aside the largest bulbs lifted from your own garden for forcing if precision timing is your goal. Cure, store, chill and plant several containers with a week’s interval between them to ensure that you have top-quality blooms at the time you desire.
Spring bulbs need special preparation prior to planting in order to be forced to bloom out of season. Because in nature they would winter through a cold, moist period followed by rapidly warming days, those conditions need to be simulated artificially if your bulbs are to bloom. With practice, you’ll be able to entice bulbs to flower on cue.
To prepare bulbs for forcing, just gather your bulbs, some dry sphagnum moss and net bags or paper sacks with punched holes, then take the simple steps shown in the following pictures and described in their captions.
Guide to Forcing
| Bulb
| Chill*
| Plant†
| Bloom∆
|
Amaryllis
(Hippeastrum) |
None |
65˚F/18˚C
3 weeks |
68˚F/20˚C
3-4 weeks |
| Crocus |
10 weeks |
40˚F/4˚C
4-6 weeks |
65˚F/18˚C
2-4 weeks |
| Daffodil (Narcissus) |
8 weeks |
40˚F/4˚C
6-8 weeks |
65˚F/18˚C
3-4 weeks |
| Hyacinth |
63˚F/17˚C
8 weeks or more |
40˚F/4˚C
6-8 weeks |
70˚F/21˚C
2-3 weeks |
| Flag iris |
5 weeks |
40˚F/4˚C
6-8 weeks |
68˚F/20˚C
3-4 weeks |
| Lily |
6 weeks |
40˚F/4˚C
6-8 weeks |
65˚F/18˚C
3-4 weeks |
| Paperwhite |
8 weeks |
40˚F/4˚C
3 weeks |
65˚F/18˚C
2-3 weeks |
| Tulip (Tulipa) |
8 weeks |
40˚F/4˚C
4-6 weeks |
65˚F/18˚C
4 weeks |
* Chill in the vegetable keeper of your refrigerator at 40-45˚F (4-7˚C) unless otherwise specified.
† Time until shoots first emerge; confirm rooting has taken place, the move indoors to area with bright, indirect light.
∆ Bloom time varies with cultivar. Extended bloom period with cool overnight room temperature, 60-65˚F (16-18˚C). |
Preparing Bulbs for Forcing
Preparing Bulbs for Forcing - Step 1
Select either lifted, cured or stored spring bulbs (or those from your garden store if available), which may have been prechilled. Choose the largest possible bulbs to use for forcing.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Preparing Bulbs for Forcing - Step 2
If desired, make a base of sphagnum moss, then layer your bulbs into a paper bag that has a few punched holes in it. Loosely close the bad, leaving air to circulate through the holes.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Preparing Bulbs for Forcing - Step 3
If your bulbs have not been treated with fungicide, place the bag of them into the humid vegetable keeper of your refrigerator. If your bulbs have been treated, choose instead a sheltered indoor spot with similar temperature conditions. Chill bulbs for at least the minimum number of weeks their species require. When that time is up, you can plant your bulbs in soil or suspend them above water in a bowl of rocks or in a hyacinth glass.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
