Plant Palette

Plant Palette

Bulb Forcing

Photo of Jennifer Schultz Nelson

Jennifer Schultz Nelson
Extension Educator, Horticulture
jaschult@illinois.edu

Although fall has barely begun, it's time to start thinking spring, at least where bulbs are concerned. This is the time of year when garden centers are flooded with dozens of varieties of spring blooming bulbs. If you don't have a yard you can plant in, consider planting bulbs in pots for forcing. It's a great way to bring a bit of spring to your balcony, patio, or even your kitchen table.

Pretty much any spring blooming bulb is fair game for forcing. The most common bulbs used in forcing are hyacinths, daffodils, and tulips.

When purchasing bulbs, choose unblemished, firm bulbs with little or no new growth. Keep in mind that for a given species, larger bulbs are more mature and will produce larger or more flowers than smaller bulbs. Bargain bulbs are no bargain if they are small for their species. They will not flower as well if they flower at all. This is one situation where you get what you pay for.

Planting bulbs for forcing is a little different than planting in the landscape. For one, planting depth is drastically different. Bulbs should be planted with their pointed tops, or noses, exposed. Spacing is also closer than in the landscape. Bulbs should be nearly touching. In a six inch pot, expect to fit six tulips or daffodils, or three hyacinths. Plant tulip bulbs with the flat side of the bulb facing the outside of the pot—this is the side the largest leaf will emerge from, and having it to the outside of the pot will create a visually appealing arrangement.

Potting mix used for forced bulbs should be fast draining. One or two parts basic soilless mix combined with one part vermiculite or perlite makes a suitable potting mix. It is important that the potting mix hold moisture, but not too much, otherwise the bulbs may rot. Water the bulbs after planting, and check them periodically to be sure the soil does not dry out completely.

In planting spring bulbs for forcing, you need space where you can keep the bulbs cool, but not frozen. A cold frame, unheated garage, shed or crawl space will work. If you have space in your refrigerator, that will work too but keep in mind that ripe fruit gives off the gas ethylene which may interfere with your bulb forcing efforts. Temperatures need to be 35-48 degrees Fahrenheit for at least twelve to thirteen weeks for successful flowering.

Potted bulbs in the refrigerator should be wrapped in plastic with a few holes cut in it to allow for air exchange. If you choose to place your pots outside, they need to be covered with at least ten inches of sand, soil or mulch to prevent the pots from freezing.

Mark your calendar as to when to begin bringing your pots indoors in the late winter and early spring. After bringing the pots indoors, place them in a cool sunny spot of 50-60 degrees Fahrenheit for the first week or so, to allow growth to begin. Many sources recommend placing a paper cone or cup over a hyacinth's bloom to draw it out of the foliage and properly elongate. They can then be moved to warmer spots in the house if desired, but realize that cooler temperatures will prolong the life of the blooms.

Some bulbs may be grown in water without added soil, such as paperwhite narcissus and hyacinths. Hyacinths need a cold period in order to flower, while paperwhites typically don't need the chilling period. Research from Cornell University suggests starting these bulbs off in pure water until roots and two inches of shoots form, then switch to a solution of one part hard liquor (vodka, whiskey, rum, tequila, etc.) to seven parts water, or one part rubbing alcohol to ten parts water. The alcohol stunts the growth of the plants by preventing the stem cells from elongating. This results in strengthening the stems, which keeps them from flopping over. This research was done with bulbs forced in water without soil, but it may be worth trying with bulbs grown in potting mix.

Most sources recommend discarding forced bulbs after they've finished flowering. I personally have a hard time doing this. I have successfully planted forced bulbs in my garden and gotten them to flower again. It sometimes has taken two years for them to flower again, but I have been pleasantly surprised by a few that flowered the year after they were forced.

Whether you replant the bulbs or not, a little effort now will definitely be appreciated when you have bright spring blooms brightening a dreary dull winter day.

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