Forcing flower bulbs is a simple way to treat yourself to indoor fragrance and color throughout the winter and early spring. It sounds harsh but, in fact, you’re simply simulating the fall and winter outdoor conditions to “encourage” bulbs to bloom earlier.
There are two types of bulbs for growing indoors:those that need a chilling period and those that don’t. Bulbs such as crocus, daffodils, hyacinths, tulips and dwarf irises are native to cold climates and require chilling to trigger blooming. While amaryllis and paperwhite narcissus originated in warmer climates, so they don’t require cool temperatures to flower.
Growing Bulbs that Don’t Need Chilling
These bulbs maybe grown in a pot (with drainage holes) filled with soil, or in a shallow bowl with a layer of gravel on the bottom to hold the bulbs in place. If growing in a bowl, add water to just below the surface of the gravel. Be sure to only cover the lower one-fourth of the bulbs and maintain the water level carefully to avoid bulb rot. For about the first two weeks hold containers in indirect light and temperatures of about 60° F, and then move to a warmer, brighter location. These bulbs will bloom in about four weeks from planting.
Gorgeous paperwhite narcissus are not only easy to force, but fragrant, too. The varieties most notable for their delicate fragrance are ‘Ziva’ and ‘Inbal’. Purchase bulbs now, store in a cool place, and consider starting them every two weeks for flowers right through the winter. Just the other day we were perusing the latest issue of Chicagoland Gardening Magazine and in it we read a practical tip for keeping paperwhites from getting tall and floppy. Research conducted at Cornell University found that when growing paperwhites in shallow containers using stones not soil, watering with a four to six percent solution of “hard” liquor the plants will flower normally, but will grow one-third shorter. Here’s what to do: Plant your bulbs as usual in gravel-filled trays and fill with plain water. About a week later, when roots are growing and shoots are green, pour off the water and replace it with the alcohol solution. To make this solution, mix one part 40 percent distilled spirits (80 proof) to seven parts water. Continue to water with this solution to keep your paperwhites shorter.
Bulb Containers and Planting
When using soil, containers should have drainage holes. Containers should not be smaller than four inches, but can be larger. They should be deep enough to allow two inches of space below the bulbs for root development, and to allow the bulbs to be completely covered with potting mix.
Place a pot shard over the drainage hole and fill the container with several inches of good quality potting mix. The bulbs should be planted with their broad bases down and their pointy noses up. You can place them close together so they nearly touch or leave space between them. Plant tulips so that the flat side of each bulb faces the outside the pot. That way, the first leaves to arise will droop attractively over the rim of the pot. Cover the bulbs with about one inch of potting mix, shake to settle the soil down but do not compress it. The soil should stay loose to encourage rooting. Water gently and thoroughly so the soil is moist throughout. Add more soil if needed to cover the tips. Label the pots with the bulb varieties, date planted, and the date when it should be removed from cold storage.
Layering bulbs is a great way to have a fuller looking pot and beautiful spring color for a longer time. Select a container that is at least eight inches deep and follow the previous planting instructions. Plant the largest bulbs (daffodils and tulips) first, leaving space between the bulbs. Add an inch or two of soil to hold the bulbs in place. Add the next layer of bulbs between the bulbs of the first layer, adding more soil. Now add the smaller bulbs. The last layer of bulbs need to be about three inches below the finished soil surface. Don’t worry if the smaller bulbs sit right on top of a lower bulb, they will all find their way to the top. This container will need at least 12 weeks of chilling.
Growing Bulbs that Require Chilling
Most spring bulbs require a chilling period to “turn on” the growth of roots and shoots in the bulb. The necessary chilling period (33° to 45° F) varies by type of bulb: tulips, 12 to 14 weeks; daffodils (Narcissus), ten to 12 weeks, and hyacinths, crocus and iris need eight weeks. Several other bulbs may also be forced: winter aconite (Eranthis hyemalis), eight weeks; Siberian squill (Scilla siberica) and Spanish bluebell (Scilla hispanica), ten weeks. Among the easiest to force tulips are the species greigii and praestans and the variety ‘Apricot Beauty’.
Place the containers in a cool dark place such as a cold frame, unheated basement, a garage that does not get below 33, or a refrigerator that does not contain fruit. Fruit naturally emits ethylene gas as it ripens which can deform or kill the buds inside the bulbs.
The soil should be moist but never wet throughout the chilling period to ensure good root development. Check the containers every week or so for dryness. You will probably find they do not need water more often than every three or four weeks. You can loosely cover the container with plastic, but check to be sure that mold is not forming. If it is, remove the covering to improve ventilation.
After the cooling period, and three or four weeks before you want the blooms, take containers from the storage area to a moderately warm spot (about 60° F). Keep them in indirect light for a few days, or cover with a sheet of newspaper. When the shoots turn green, move them to a spot that gets direct sun but relatively cool temperatures (less than 65° F in the day and about 50° F at night). The cooler the temperatures the longer the blooms will last. Water the bulbs as you would a houseplant, they will require much more water now. Don’t let the soil dry out, but don’t overwater, either. Give the pot a quarter turn regularly so the growth does not become lop-sided.
With a little planning and preparation now you can release the pure potential of spring flower bulbs and encourage them to add beauty and fragrance to your home all winter. Visit The Growing Place for all the advice and supplies you’ll need to be successful.
Posted on 10/22/2014 at 7:30:00 PM