Forcing Bulbs

San Antonio Express News
Sunday, November 13, 2005

By Dr. Jerry Parsons

Americans buy a billion bulbs a year, mostly from Holland. This figure includes all corms, and tubers, as well as truebulbs. One way of enjoying these bulbs is by forcing them indoors (no, this doesn’t involve violence!).

Crocuses, hyacinths, and the early blooming cultivars of narcissus are the best bets as forced bulbs. The cost of flowers is far less than it would be to buy them potted or cut at the florist’s.

The term “forcing” means getting a plant to produce its shoot, leaf, and flower ahead of its natural schedule. To force hardy bulbs and ‘Paperwhite’ narcissus you need to mimic and compress the process the plant would undergo in the garden.

When buying bulbs for forcing, always choose first rate, top size varieties. Don’t buy ones that are soft or sprouting. You know the old saying, “You get what you pay for.”

To begin the forcing process you must first pot up the bulbs. Use clay pots because they breathe and look pretty. They’re also heavy enough to keep the blooming plants from tipping over. They should be absolutely clean. Pots can be run through the dishwasher after rinsing off any soil. Next, put a piece of crockery, or a rock, over the drainage holes in the bottom of the pots to keep the soil from running out. Since bulbs need moisture, some food, and perfect drainage, use a good commercial potting soil or mixture of equal parts milled sphagnum moss, potting soil, and sand, vermiculite, or perlite. Plant the bulbs with the pointed ends up, as close together as possible without letting them touch. Cover the tops with half an inch to an inch of potting soil, leaving an inch of space below the pot’s rim to allow for watering. Water well after the bulbs are planted. Don’t water again until the clay pot dries to a light pink.

Next put the pots in a cool, dark, sheltered place, to initiate root, then shoot growth. Cold storage is a critical step in forcing. Ideally, temperatures should be between 38 and 48 degrees Fahrenheit. One could use a refrigerator set to around 45 degrees. If you can’t afford the space in the refrigerator, at least try the narcissus described here, as cold storage is not as critical.

Leave hardy bulbs in the cold for at least 10 to 12 weeks, or until you see shoots nosing above the soil and fine white roots coming out of the drainage holes. ‘Paperwhite’ narcissus should be left in cold for only two weeks, at which time they should begin pushing their white shoots up through the soil. Next will be the iris, probably, then the crocus or perhaps the early blooming tulips. Then come the hyacinths, which will get you through February, and finally the daffodils and the other tulips. Watch the plants closely for development, then bring them into a warmer, well lighted area.

Before bringing the plants out into the warm dining room for show, let them sit on a shelf in a cool place, such as an unheated entryway, enclosed porch, or closed off back room. There should be indirect light (north or east) and temperatures in the 50s. Here the plants will green up and grow taller, and their flower buds will mature. This will take from one to four weeks, depending on the type of bulb.

The last step in the process, the actual forcing, is the easiest and the most thrilling. Move the plants into a warm room, pull up a chair, and watch them bloom, weeks or even months before they would outside. Of course there will be gaps here and there in your indoor flower show. Tulip blossoms aren’t noted for their longevity. On the other hand, hyacinths will bloom for nearly two weeks if the room is between 65 and 68.

Other minor bulbs to try include grape hyacinths, and Dutch irises.
Dutch Hyacinths are the easiest hardy bulbs to force. Their many one and a half to two inch wide florets look like doll’s slippers when in bud and lilies when in bloom. Everyone who sees them and smells their fragrance will want one.

Plant only one hyacinth per four inch plastic pot. Use plastic rather than clay in this instance because hyacinths seem to demand more water than the other plants and plastic holds moisture better. To promote proper length and better development of the flower stems, cover the pots with a cardboard box that has some holes punched in it for ventilation. Keep the plants under the box until the stems are several inches tall in the bird’s nest of leaves. Then remove the box and bring the plants out.

Keep hyacinths in an intermediate room until their buds show color. They grow eight to 10 inches tall and get quite top heavy. Before they topple, sink the plant, pot and all, into a 14 inch tall pot and pack damp peat moss all around.

Six “Paperwhite’ narcissus, can be brought up quickly in a warm room. The more frequent problem is delaying them, which you can do by storing them dry at 50 degrees until you are ready to pot them up. Then give them two or three weeks, to make roots in the cold. This is also necessary so that the roots don’t push the bulbs out of the soil, as they tend to do when potted up and set immediately in a warm room. They need only another week or so at room temperature to bloom. Some people like to force ‘Paperwhite’ in pebbles and water.

In a closed, overly warm room ‘Paperwhite’ can be quite fragrant. Narcissus get floppy and need support; the green metal hoops you can buy work, but can also be sank in larger pots, and the container padded with some kind of damp florist’s moss.

Wait until the daffodils have good shoots several inches tall, with the whiter leaf sheath showing above the soil, before moving them into the intermediate stage. Let the buds start to break open before you bring them into the dining room.

Tulips take the most care and time to force. They are leafier and less droopy than cut tulips and make better arrangements. Plant tulip bulbs with the pointed end up and flat side against the outside of the pot. Leave the pots in the cold for at least 12 weeks no less. At the end of this time there should be a smooth ivory spike at least an inch above the soil. You can then bring them up into temperatures absolutely no higher than 60 degrees. It may take another several weeks before the buds are distinct and colored, the leaves unfurled and green enough to show them off to fellow bulb lovers. Because people love tulips, some nurseries are offering pre-chilled tulip bulbs which can be ordered in the next two days from:

After blooming, the ‘Paperwhite’ and other narcissus may be planted into the landscape for future bloom. All others should be discarded.

Dr. Jerry Parsons is a Professor for Texas A&M University and a Texas Cooperative Extension Horticulturist for over 30 years in South Central Texas. For more information on this or other horticulture topics, go to and our County Extension website at

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