Forcing Flower Bulbs
Forcing Bulbs Indoors
The opportunity of having a whole season of flowering daffodils, tulips, and hyacinths indoors during winter is a reality. Little (minor) bulbs, such as snowdrops, scilla, muscari, chionodoxa, and crocus force equally well as the large (major) bulbs, daffodils, tulips, and hyacinth. Both the major and minor bulbs are handled in the same way, although the forcing period may vary slightly. Some cultivars (early cultivars and those that do not grow too tall) are better suited for forcing than others. Catalogs will usually identify forcing varieties.
The term "forcing" refers to inducing a plant to produce its shoot, leaf, and flower ahead of its natural schedule and out of its natural environment. To force hardy bulbs you need to mimic and compress the process the plant would undergo outdoors in the garden.
Type Of Pot
The type of pot (plastic versus clay) is a personal preference. Plastic pots do not dry out as rapidly as clay, are easier to clean and lighter in weight, as well as less expensive. Clay pots have aesthetic qualities in and of themselves and don't necessarily need a basket or covering to be attractive. Bulbs will grow equally well in either. The pots should be scrubbed clean before use and clay pots soaked for several hours to saturate pores.
When Forcing Bulbs, SIZE Is Important!
When buying bulbs for forcing, always choose first-rate, top-size varieties. If purchasing through mail-order, order bulbs by August or earlier to ensure adequate time to receive the bulbs by the first part of October. If you buy from the local garden center, scrutinize them the way you would produce at the grocery store; don't buy bulbs that are soft or sprouting. High-quality, large bulbs are necessary because the bulb contains the food required to produce a flowering plant.
Type Of Soil For Forcing Bulbs In Containers
Since bulbs need moisture and perfect drainage, a mixture of equal parts peat moss, potting soil, sand and vermiculite or perlite is best. Mix thoroughly and moisten with enough water to a damp consistency. If you anticipate planting bulbs outdoors after forcing, add 1 teaspoon of 5-10-5 dry fertilizer to every quart of soil mix to give the bulbs an extra boost after flowering. Hyacinths, crocus, and narcissi can be grown in pebbles and water - with no additional nutrients, however, they are usually completely exhausted and should be disposed of after blooming.
Planting Bulbs In The Pot
The next step in planting is to place a few pieces of broken crockery over the drainage holes, to prevent the soil from running out initially and clogging later. Fill your pot half-full of soil mix, then adjust the soil level until the tops of the bulbs reach the rim of the container. Plant bulbs with the pointed ends up, as close together as possible, without letting them touch. Tulip and other bulbs with a flat side should be planted with the flat side facing the edge of the container. This will allow the first leaves to form a border around the edge of the pot.
Add enough soil mix to fill the pot, and water the bulbs thoroughly from the top or immerse in a tub of water - this will settle the soil around the bulbs. Label each pot with the name of the cultivar, date of planting and date to bring out of cold storage.
How Many Bulbs Per Pot?
Daffodils, narcissi, crocus, muscari and other bulbs look great in pots when planted in groups of three, five, or more. Hyacinths look quite handsome when planted singly, or in groups. Dense plantings are recommended for minor bulbs.
What To Do After Planting?
After planting, place the pots in a cool, dark place, such as a cellar or refrigerator to initiate root and shoot growth. Other suitable environments include an insulated cold frame, under a porch, or an unheated garage. Cold storage is a critical step in the forcing process. Ideally, temperatures should be 35 to 48 degrees F. If necessary, set boxes, pots or black garbage bags over your potted bulbs to keep them dark during the cooling period. The medium should be kept moist through the rooting and cooling period. After five or six weeks, the roots should emerge out of the bottom of the containers of the large hardy bulbs.
How Long To See Blooms on My Forced Bulbs?
Forcing will take about 12 weeks for the early blooming bulbs (snowdrop, crocus, daffodil) and about 16 weeks for the tulips. Longer cold storage will result in taller flowers, while storage time shorter than 13 weeks will result in smaller plants and sometimes aborted flowers. A good rule of thumb: when you see the shoots 2 to 3 inches above the soil and fine white roots emerging from the drainage holes, it's time to bring the pots out of cold storage. At this stage of development, move the bulbs to a cool location, such as an unheated entryway or closed off back bedroom, where the temperatures are in the ’50s. Bulbs should be placed in indirect lighting and should not be allowed to dry out.
Fertilizing Forced Bulbs
Feed weekly with a half-strength solution of houseplant fertilizer. Turning the pots every day or so keeps the flower stems straight and strong. In a week or two, the stems will elongate and the buds will become plump. When the foliage and buds are well developed, move the pots to a bright, sunny window in the house, where temperatures are near 65 degrees F. Once the flowers begin to open, take the plants out of direct sunlight to prolong the bloom.
You will be pleased at how quickly the bloom unfolds compared to weeks, or possibly months, before they would outside. Hyacinths will bloom for nearly two wonderfully fragrant weeks if the room is between 65 to 68 degrees F. Iris reticulate and crocus may fail to bloom or last only a day if temperatures get over 65 degrees F.
What To Do After Forced Bulbs Have Flowered?
After flowering, cut the flower stems and place the pots in direct sunlight, keeping the foliage growing until it begins to die back. As it withers, don't pull the leaves off, store the bulbs in the pots in a cool, dry place until late summer or early fall, at which time they can be planted into the garden. Attempts to force the same bulbs indoors will be unsuccessful, as forcing weakens the bulb and the bloom will be small and unsatisfactory the following year. Once the bulbs are back in the garden setting, they will return to a natural schedule, and in several years will again produce a wonderful show of flowers.
Suggested Bulbs for Forcing
Spring Flowering Bulbs (Crocus, Daffodils & Tulips):
Spring-flowering bulbs need a longer period of chilling to bloom. Crocus, daffodils and tulips are all suitable for forcing, but some varieties work better than others (and are often listed as suitable for forcing in catalogs). Shorter varieties tend to make a better indoor display and won’t flop over as easily. And regardless of the type or variety, use the largest bulbs you can get, since the flowers will be larger. Tulips tend to be more difficult to consistently force, with daffodils less so. 'Tete-a-Tete' is a very good variety of small daffodil for forcing. Hyacinths, crocus and grape hyacinths are easier to force.
Preparing the bulbs for forcing is simple. Choose pots with a drainage hole(s) and fill the containers partway with a light, well-drained soilless potting mix. (You may want to put a layer of gravel in the bottom of the pot before adding the potting mix.) Place as many bulbs as you can in the pots without them touching each other or the sides of the pot - crowding them in gives a better show of flowers. Add enough potting mix over the bulbs so they are sticking out of the soil about halfway. Water the pots well.
The planted pots then need to be chilled for 10-12 weeks at 40-50 degrees F. You can just place them in a refrigerator, but some people have good results keeping them in an unheated garage or a cold frame, as long as the temperature doesn't drop below 20 degrees F. But too much freezing and thawing will cause the bulbs to rot, so the consistent temperatures in a refrigerator ensures success. Check the pots periodically and water as necessary to keep the soil moist, but not wet. If you're using a refrigerator, you can cover the pots with an open plastic bag, which reduces the need for frequent watering. You can also place the well-watered pots in a closed plastic bag that won't be opened again until taking the pots out. Doing it this way the soil surface and bulb tops might become covered with an ugly-looking, but harmless, mold that disappears within days and the plants will bloom perfectly. If you're potting bulbs on more than one date, label the pots so you know when to take each out.
Two to four weeks before you want them to bloom, take the pots out of the refrigerator and move them to a warm spot in indirect light for a few days. Then when the sprouts have greened up, transfer the pots to the sunniest window you have, and continue to water as necessary.
Here's some suggested varieties of spring-flowering bulbs that are good for forcing:
Tulips: Apricot Beauty, Bing Crosby, Edith Eddy, Mirjorma, Yokohama, Jingle Bells, Attila, White Dream, Princess Victoria, White Swallow, Estella Rijnveld, Calgary, Gudoshnik, Red Riding Hood, Stresa
Daffodils: Barrett Browning, Dutch Master, Ice Follies, Golden Harvest, Salome, Pink Charm, Flower Record, Louis Armstrong, Unsurpassable, Tete-a-Tete,
Crocus: Pickwick, Rembrance, Flower Record, Peter Pan, Purpurea Grandiflora
Hyacinths:
If you don't have room in the refrigerator for a bunch of pots of soil, try forcing hyacinth bulbs. Simply put them in a paper bag in the refrigerator, for 4-6 weeks. Bring them out and put them in specially designed forcing vases filled with water just up to the base of the bulb. Place them in a bright window and in about 4 weeks you should have beautiful, scented hyacinth flowers!
Suggested varieties of hyacinth/muscari for forcing: Blue Spike, Early Giant
Paperwhites
Paperwhites are often forced in a shallow pot or bowl (without drainage holes). A clear container lets you see the roots developing and makes it easier to gauge the water level. After filling the pot about two-thirds with pebbles, gravel or soil, place as many bulbs (flat end down) in the container as will fit without touching each other. Then fill in around the bulbs. Add water to the pot until it just reaches the bottoms of the bulbs. Place the container in a cool, dark spot (45-50 degrees F) to encourage root growth. In about three weeks, after roots have developed, move the pot to a cool, sunny spot. Sprouts will quickly develop and soon thereafter blooms. Keep the water level just at the base of the bulbs. The fragrant flowers will last 10 days to several weeks in cool conditions (less if it's warm). You can adjust the bloom time a little, by adjusting temperature and watering. If the plants are developing too quickly, move them to a cooler spot and reduce watering, but if you need to speed them up, put them in a warmer place. You can stake the stems if they start to flop over.
Here's some varieties of paperwhites good for forcing: Bridal Crown, Spell Binder, Jenny, Cheerfulness
Amaryllis
Plant amaryllis bulbs in containers with a drainage hole (and saucer to catch water run-off). These large bulbs are often potted individually, in a pot an inch or two larger in diameter than the bulb, but several can be combined if you have a large enough container. Soak the bulbs and roots overnight in lukewarm water before potting. Place a layer of gravel in the pot and add a few inches of soilless potting mix. Place the bulb on top of the potting mix so that the top of the bulb is barely above the rim of the pot, and fill with more potting mix around the bulb, leaving the neck exposed. Water well, and place in a cool, sunny spot. Water sparingly until a sprout forms, then water more frequently to keep the soil moist. It will take six to eight weeks for the plant to bloom.
Other Good Bulbs for Forcing
Snowdrops, Dutch Irises, Blue Squill, and Glory-of-the-snow
SEE: Pruning Spring Flowering Bulbs After They Bloom
SEE: Forcing Flower Bulbs Indoors
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