FORCING SPRING BULBS
I never grow old of the favourable comments we receive about the breathtaking display of Daffodils, Tulips and Hyacinth at Government House toward the end of January. There is no quicker way to lift a person’s spirit than to bring spring indoors while snow accumulates outside. A pot of spring bulbs seems to answer the calling. Many different bulbs can be forced including tulips, daffodils, hyacinths and crocuses. All of these bulbs need a 12 to 15 week pre-coding period before they can be brought into active growth. This period of enforced cold tells them winter is at hand. When they’re brought indoors to a warm setting, they assume spring has arrived and they set bloom.
Large bulbs marked for forcing are purchased and the process started in mid October. There are many different pots and containers that can be used, but I prefer potting several bulbs together in a 6 inch bulb pan and 12 to 14 bulbs in an 8 inch bulb pan. Large flowered Hyacinths look regal when planted 3 or 4 to a 6 inch pan.
Bulbs store all their nutrients that the plant needs to bloom so they do not need to be potted in a rich nutritious soil. When planting in pots, the tips of the bulbs should just peek above the soil line, which should itself be ½ inch below the pot rim. Then, water the soil well and they’re ready for winter. Keep the soil moist from this time until flowers fade and foliage yellows, signaling the end of a growth cycle.
Tulip bulbs need special attention when potting. They are asymmetrical, having a curved side and a flat side. The largest leaves will grow from the flat side. To ensure they arch out over the rim of the pot, put the flat side of the bulb against the outer rim.
Government House is fortunate to have a root cellar on site which provides the required darkness and 35 – 45 °F/2 – 7 °C required to force bulbs during winter. If a root cellar is not a viable option, there are a couple of other locations one could consider. If you can sacrifice the space, a refrigerator could provide suitable environmental conditions. Place the container in a black polythene bag and store them away from apples and other fruits which give off ethylene gas that can cause bulbs to rot, or flowers to abstain from developing. If you have a cold frame that you can mulch carefully so the interior won’t freeze, this could also provide favourable conditions. Whichever method you choose, bulbs must not be allowed to dry out or freeze during this forcing period.
After 12 weeks, I look for two signs that the bulbs are ready to be brought inside. They are; the roots showing through the pot’s drainage holes and a green shoot emerging from the tops of the bulbs. From early January to late April, I usually bring out about 20 pots of assorted bulbs each week. Pots are placed in a bright, cool location until shoots are about 4 inches tall. They are then moved into bright sun until buds show colour, at which point they are moved back into bright, indirect light. While plants are in flower, they prefer cool nights and days no warmer than 65°F/18°C. At this point, the soil is kept constantly moist and fertilizer withheld.
Most bulbs will not produce a second display indoors. Since they grow in such cramped conditions, it is difficult for them to store the nutrients needed to bloom again. Though I would not discourage any garden enthusiast from planting forced bulbs in the garden, in my experience it is a hit or miss proposition if mass blooms are desired. Forcing uses up about 80 percent of the bulb’s energy so they never become peak performers in the garden.