To force a bulb means that you are manipulating its environment so that it will bloom out of season. Before spring flowering bulbs can be forced to flower in a container, they require a cold period of 12-15 weeks at temperatures between 38°-48°. This allows production of a good root system. A spare refrigerator is excellent for chilling the potted bulbs. I have even used my basement window wells and covered the pots with a heavy layer of straw…much to the delight of the field mice!
Paperwhite Narcissus and Amaryllis do not need to be cooled when you buy them. They have already been prepped for forcing by the supplier. Plant them as directed, set them in a sunny location, and let nature take its course. Paperwhites can also be grown in water, much like hyacinths.
Hyacinth bulbs are first chilled in a doubled paper bag for 13 weeks and then set in a special water vase to grow; the basal plate of the bulb must touch the water for the roots to start developing. To prevent diseases, Hyacinth bulbs are treated with an agent that will irritate skin. Be sure to wear thin plastic gloves and wash after handling.
Forcing spring bulbs in a container is simple. Select a container from 6-24” wide with good drainage. Fill 2/3rd full with a good potting mix; do not use garden soil or fertilizer. Plant the bulbs so they almost touch each other and cover with more potting mix, leaving about a half an inch from the top. Tag your pot with start date and cultivar. Water the container and place it in a cold (38°-48°) dark location for the duration. Check it periodically to be sure the mix has remained damp, but not wet. Too wet and the bulbs will rot.
The number of bulbs for a 6” pot: narcissus, 3 large bulbs and up to 6 if smaller bulbs are being used; paperwhites or tulips, 5-6; hyacinths, 3; minor bulbs like muscari or crocus, 12-15.
For a 24” pot and using a single kind of bulb you will need up to 50 tulips or smaller narcissus, or 30 of the larger flowering narcissus, and possibly 80-100 of the minor bulbs.
When using one kind of bulb per container, create several containers with staggered blooming periods. You can also plant an assortment of bulbs in one larger container but be sure they have the same bloom period. When using an assortment of bulbs, plan on layering them in the container. Plant the larger bulbs deeper and first, add potting mix and then place the next layer of bulbs on top and add more mix. End with the minor bulbs planted closer to the edges, keeping mix a half inch from top.
As time draws near for removing your containers from the cold treatment, you may see pale whitish tips emerging. This is the start of your bulbs, and once placed in the light, they will soon begin photosynthesis and turn green. It won’t be much longer and your blooms will emerge for the long awaited color!