Forcing Spring Indoors 

The chilling facts

With all those spring flower bulbs now on sale, it's a crime not to plant a few outdoors before the ground freezes. However, if digging in the dirt is out of your blood for the season, consider forcing bulbs for later enjoyment. Forced bulbs make wonderful gifts.

The term "forcing" might better be expressed as "fooling"—for what the gardener really does is fool the bulbs into acting as if winter is over and it's time to flower. Two of the easiest bulbs to force are paperwhite narcissus and amaryllis. Neither bulb needs a chilling period.

Let's talk about paperwhites first. Paperwhites (Narcissus tazetta) are the most popular forcing bulbs and the easiest. They grow 12 to 18 inches tall and are identified by their sunburst of white petals surrounding a shallow white cup in the middle of each blossom. The bulbs will produce abundantly—up to three flowering stems per bulb with numerous blossoms on each stem. The most common color for paperwhites is, of course, white, but a golden yellow variety exists as well, called Grand Soleil d'Or. It has a shallow orange cup in the middle surrounded by yellow petals. Paperwhites have a fragrance that's out of this world and so strong that it can literally drive you out of the room or house.

To pot up these fragrant ones, use a medium of soil or pea gravel. If gravel is used, any container that holds water will do, but a shallow glass dish is best (like a Pyrex baking dish). A clear container allows you to check the water level and the progress of root growth. It is important to keep the water level in the gravel just below the bulb (otherwise the bulb will rot). A little charcoal in the container keeps the water clean.

Place the bulbs so that only the bottom half of the bulb is covered with gravel, the top half should be exposed. Flowering will take three to five weeks. A cool spot with low light will help the roots to form, after that, move the pot to a sunny location to encourage bloom.

Amaryllis, like paperwhites, do not need pre-chilling. Their impressive 12- to 24-inch-tall showy flower stalks can produce massive trumpet-shaped blooms 6 inches long and 8 inches across. Flower colors run from red to pink and white to salmon. Native to tropical South America, there are 80 species of amaryllis (Hippeastrum hybrid) ranging from miniatures to the giant flowered ones. Being a tender bulb from the tropics, it is kept indoors except during the summer. Forcing takes six to eight weeks.

Amaryllis is well worth the cost. Each bulb can send up one to two thick flower stalks with four blooms per stalk. One year I received an amaryllis from a friend that produced two stalks with six flowers per stalk. The only thing missing with these flowering giants is fragrance, but their beauty and sheer exuberance makes up for it.

Place one bulb per pot, allowing only an inch of space between the bulb and pot. Amaryllis does best when its roots are a little crowded. Leave the upper two-thirds of the bulb exposed above the soil. Position in a sunny location and water sparingly until shoots appear. Once growth begins, fertilize and water as you would any houseplant.

After blooming stops, keep the leaves growing until midsummer. In August allow the plant to dry down and go into its needed six to eight week rest period. After the bulb has rested, it will start growing new shoots again and can be repotted and kept for many years following this cultural regime.

Other fun bulbs worth forcing include hyacinths, crocuses, miniature bulb irises (Iris reticulata), tulips, grape hyacinths (Muscari) and dwarf narcissi or daffodils. All these bulbs will require a chilling period of 12 to 15 weeks unless purchased pre-chilled. This chilling time is used by the bulbs to produce a good root system, which is essential if they are to be forced into flower.

To chill bulbs outdoors, plant them in clay pots filled with soil mix and water well. The soil mix should be one-third each of peat moss, perlite or vermiculite and potting soil with a tablespoon of slow acting fertilizer mixed into the soil of each pot. Make sure a half-inch of their tops show above the soil and don't forget to leave room for water between the soil and the top of the pot. Insulate the pots with leaves and then cover the leaves with sand. An unheated garage or coldframe can also be used for chilling if temperatures there remain between 35 and 48 degrees Fahrenheit.

The temptation to put potted bulbs in the refrigerator for chilling only works if no fruit or vegetables are kept in the fridge with them. Produce, especially ripening fruit, gives off a gas that can kill the flower bud inside the bulb. Keep the soil moist but not overly wet throughout the chilling period. Once the chilling time is complete, place the pots in a warmer spot (approximately 60 degrees Fahrenheit) in indirect light for a week. Once their shoots turn green, move them into direct sunlight. Cool temperatures—less than 65 degrees Fahrenheit during the day—will keep the flowers fresher longer. Water the potted bulbs as you would any houseplant.

Once forced to bloom out of season, bulbs can take three years to bloom again outdoors, often gardeners just discard them.

Suzann Bell is a horticulturist with the University of Idaho Extension in Ada County. Send gardening questions to Suzann c/o Boise Weekly or e-mail: sbell@uidaho.edu.

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