November 12, 2012 - 11:09 am - Posted in News

Christina Lloyd, ISU Extension and Outreach Agriculture and Natural Resource Intern

Clippings: A Weekly Column about Plants, Gardens, & Yards

By: Christina Lloyd, ISU Extension and Outreach Agriculture and Natural Resource Intern

As we are entering our last five weeks of fall, it’s not hard to imagine the upcoming winter months we have ahead of us. If you’re anything like me, than spring fever usually sets in for you at about the same time as winter, which leaves us longing for the spring. However, recently I was introduced to the idea of forcing bulbs, which is the manipulation of bulbs so they flower out of their natural season, providing blooms during a time of snow.

When forcing bulbs, there are five essential things that are important to remember. These are type, container, planting, chilling, and forcing. Type is the most essential part of the forcing process. When forcing bulbs you want to make sure that the bulbs you are using are of flowering size and good quality. Bargain bulbs may be tempting but for the use in forcing they don’t work as well.

The next aspect of forcing bulbs is finding and using the right container. For the most part, any sort of container will do whether it is metal, ceramic, plastic or clay as long as it is clean and sterile, has adequate drainage and is at least twice as deep as the bulbs to be planted. Another type of container that is commonly used is a forcing vase. Narcissus, hyacinths and crocuses are the most common type of bulbs that are grown this way. This container holds the bulb in the top of the vase and allows the roots to grow downward into the water that is in the bottom.

When planting, the first step is to ensure proper soil consistency. One recommendation for soil that works well consists of one part garden soil, one part peat moss and one part perlite. To help facilitate drainage small pebbles can be added to the bottom of the container before the soil. The container should be filled three fourths of the way full with the soil mixture. The bulbs are then placed on top of the soil. Keeping the flat side of the bulbs next to the rim of the container is useful because this is where the largest leaf usually grows out and can then drape over the container. After the bulbs are placed where you want them, surround them with additional soil until only the tips of the bulbs are showing. Lastly, you want to water your bulbs thoroughly. Once this is done it’s time to move on to chilling.

Chilling is the key to manipulating the plants life cycle. It forces the bulbs to think they went through a winter. This can be done in a variety of ways from placing them in a cold frame, an attic, a cellar, a garage, or a refrigerator. When using a refrigerator, the bulbs should be kept separate from any fruit in the fridge as the chemicals given off from the fruit can affect the plants growth. In addition, soil moisture levels should be monitored when using the refrigerator because the soil has a tendency to dry out in this environment. A cold frame can be used by digging a trench that is one foot deep and as wide and long as needed to fit all of your containers. Cover the containers with soil, leaves, or straw to buffer the bulbs from the cold and prevent them from freezing. While the plants are in the chilling process, they should remain at a temperature between 35 to 50 degrees F and in an area with minimal light for 12-16 weeks.

After the bulbs have chilled for the appropriate amount of time they can finally be forced. The first step is to remove the desired bulbs from chilling and place them in a cool, semi-lighted area that is between 60 to 65 degrees F. Leave them here until the shoots turn green, which usually takes between four to five days. After the shoots turn green the plants can be watered and moved to a warmer and more brightly lit area. They should bloom within the next 2 ½ to 3 ½ weeks.

When forcing bulbs, several types of bulbs can be placed in one container to create arrangements. You can also stagger your bulbs to have continuous blooms throughout the winter. Lastly, to help prolong a bloom, you can put it back into a cool spot at night.

I hope this gives you hope for a hint of spring during the season of snow ahead of us. For any questions, please feel free to contact me at my email clloyd@iastate.edu, by phone at (712) 737-4230 or through your local County Extension office. Additional information was provided by the Iowa State University Extension article Forcing Flower Bulbs (March 2001), the Purdue University Cooperative Extension Service article Forcing Bulbs for Indoor Bloom (July 2005), the University of Minnesota Extension article Forcing Bulbs for Indoor Beauty in Winter (2012), and the University of Rhode Island Landscape Horticulture Program article Forcing Bulbs: factsheet.

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