Forcing bulbs for winter bloom

Posted by: Irene Shonle, Gilpin County Extension

Although it’s probably too late to plant bulbs outside for spring bloom, you can still plant them for indoor bloom. Even better, indoor bulbs will bloom earlier than they would outside ---right when winter seems endless and you really need that pick-me-up. Unless you already bought bulbs and didn't get a chance to plant them, at this time of the year, your best bet for finding bulbs will be online retailers. 

 

Amaryllis bulb (Irene Shonle)

Paperwhites are the standard for indoor forcing because they are the easiest. They require no refrigeration, and will bloom reliably about 6 weeks from planting. They don’t even require soil – water will work fine.  Amaryllis are the second most popular indoor bulb, and the ones you buy in the store have usually been prechilled or dried down to bloom after about 6 weeks as well. However, other bulbs such as tulips, narcissus (daffodils), hyacinths, crocus and grape hyacinths will all come beautifully into bloom with just a little more effort.  I particularly like planting tulips and crocuses indoors, since the critters eat them more often than not outdoors.

 

Hyacinths (Plant Talk Colorado)

In planting bulbs for indoor forcing, it is easiest to plant all the same variety in one pot so you don’t have to worry about different chill and development requirements. Loosely fill the bottom two inches of the container with potting soil. Plant the bulbs close together in the pot – typically they are planted much more closely together than bulbs planted in the ground. Plant 6 tulip bulbs, 3 hyacinths, 6 daffodils, or 15 crocus for a 6-inch pot. Place the bulbs in the planting mix with the pointed side up. The soil under the bulbs should be loose so that the roots can grow freely. Add more loose soil, but don't bury the bulbs -- leave the tops of the bulbs exposed. With tulips place the flat side of the bulb next to the rim of the pot since the largest leaf will always emerge and grow on that side, producing a more attractive pot. The bulbs should be watered immediately upon planting, and thereafter the soil should never be allowed to become dry. 

After planting, immediately put the pot into a dark and cold spot. Bulbs (except paperwhites) must be given a dark and cold (35– 48 degrees F) temperature treatment for a minimum of 12–13 weeks. This cold treatment can be provided by an unheated garage, attic, basement, or crawl space, as long as the bulbs don’t freeze.   Make sure to check that the soil doesn’t dry out during this period; water if necessary.  It is easy to forget about your bulbs, so mark your calendar to remind yourself when the first pots can be removed from storage for forcing to begin. For example, if you plant in early November, bring in the first pots in late January to early February. For a continuous supply of flowers, bring in a few pots at weekly intervals. On average, the bulbs will flower in three to four weeks; closer to spring, they flower more rapidly.

In the home, place the pots in a cool, bright location. A temperature of 50–60 degrees F is preferred for the first week or until the shoots and leaves begin to expand. Then, they can be moved to warmer locations (or can stay in the cooler temperature, but they will not bloom as quickly). Discard tulips, narcissus, crocus, paperwhites and hyacinths after flowering as they normally are "spent" and are not likely to ever flower satisfactorily again (although if you feel like gambling a little effort, you could dry down the tops of the bulbs and try planting them in the garden. They may bloom in a couple of years).  Amaryllis, on the other hand, can be kept in a pot and brought to rebloom yearly: http://www.ext.colostate.edu/ptlk/1303.html.