Forcing Spring Bulbs
By Andy Conrad:Â Pike County Master Gardener Coordinator
Have you ever thought about bringing some of beauty of spring into your home during the winter months? Forcing spring bulbs can fill your home with fragrance, freshness, and bright colors-just when you need it most. Forcing bulbs is described as the flowering of the bulb out of season or out of its normal environment. Spring bulbs can be potted any time from October through December for winter flowering. Bulbs that can be forced include hyacinths, tulips, crocus, daffodils, and paperwhite narcissus.
What is “forcing?”
Forcing is a term used to describe the process of manipulating a plant’s growing environment, allowing it to bloom earlier than usual. All hardy bulbs require a cold or chilling period and then an increase in temperature in order to bloom. A bulb planted outside in the fall and winter gets this cold period naturally and has to wait for warmer spring temperatures to bloom. The forcing process mimics the outdoor winter climate but brings it into warmer temperatures before nature is able to provide it. This premature dose of warm weather is what “forces” the blooms to emerge earlier than naturally possible.
Normally, bulbs require 12 to 13 weeks of cold treatment to ensure adequate rooting and the needed 1 to 4 inches of top growth. After this period of time the bulbs can be brought into a cool, sunny location. A temperature of 50 to 60 degrees for the first week is preferred or until the shoot and leaves are extended. They then can be moved into a warmer location. It is best to avoid direct sun. Hyacinths may have a tendency not to have an elongated flower stem and hence “stick” in the clasp of the leaves. You can overcome this by putting the plants in the dark for a few days in order to “draw” the flower out of the bulb. Once in flower, cool temperatures (especially at night) will prolong the flower life.
How do I “force†my bulbs?
Forcing is easy to do. All that is needed are the proper supplies, location, and a little planning and patience. Use a good potting soil to plant the bulbs. Do not worry about proper spacing – it is better to have your bulbs placed close together to have a good showing of blooms. Fill the pot 2/3 to 3/4 full of soil. Do not pack the soil. Place the bulbs on the soil and fill the pots to within ½ inch of the rim. Only the necks or tips of the bulbs should be showing. Water well and never allow the soil to dry out. A temperature of 38 to 45 degrees is ideal for rooting. These temperatures can be found in the main part of your refrigerator or in an unheated garage. Temperatures that are too cold will slow the rooting process; whereas warmer temperatures will hasten top growth before the roots are well established. Check your bulbs regularly for the required growth.
Paperwhite narcissus are the easiest bulbs to force as they do not require a cold treatment in order to bloom. Another method for forcing papwerwhites is to select a container, dish, or shallow bowl. Fill the container halfway with pebbles, stones, or marbles. Settle each bulb into the pebbles. Fill the container with water until the bottoms of the bulbs are touching. Even though paperwhites do not need a cold storage, they should be started on the cool side and then moved to a sunny window in your kitchen or living room. This gradual temperature change will discourage the paperwhites from becoming stretched or too leggy. They will flower in three to five weeks and their fragrance will permeate the air.
And after the show is over . . .
Once the blooms have faded, cut back the flower stalks. If you intend to keep the bulb, allow the leaves to remain and continue watering until they have died back on their own. Store the bulbs in their pots in a cool, dry place until autumn, and then plant them outdoors. Do not try forcing the same bulb over and over. A forced bulb will only bloom once indoors without another cold storage treatment. Forcing uses a lot of the bulb’s energy and food reserves. Next year’s garden display of this previously forced bulb will no doubt be less – experience has shown that some bulbs will never bloom again. Paperwhite narcissuses are not hardy and will not bloom again, indoors or out.
You can sometimes find “sale†bulbs this time of year at your local home and garden centers. You can also order bulbs over the Internet. You can also look for bulb forcing kits that will have all of the materials needed to complete this project.
This article is based on material taken from http://www.ext.nodak.edu/county/cass/horticulture and http://berks.extension.psu.edu/MG.
© Copyright 2010 Connections Magazine
