Forcing Bulbs

With cooler weather arriving here in the suburbs, many of us are already thinking ahead to the cold winter months. We’re getting our gardens prepped, our leaves raked and our bulbs planted. But did you know that now is a great time to get started on a winter project? One that will bring you beautiful blooms during the cold, gray days of January and February?

Forcing bulbs is a great way to sneak a little bit of spring into your home during those long winter months.  To force bulbs, however, you will need to start them now. They’ll do the majority of the work, but you’ll have to help them a little along the way.

The reason forcing bulbs starts now is that you are tricking the bulbs into thinking they’re growing in the spring.  In order to do that, you’ll need to chill the bulbs, as if they are in the cold ground during the winter.  Chilling the bulbs can take anywhere from 8-15 weeks, depending on the bulb. Paperwhites and amaryllis, however, do not need to go through this chilling process. This is one reason they are so popular during the winter months. Paperwhites can also grow in almost any medium: soil, stone or water.  The forcing process covered here is for other bulbs, like hyacinths, tulips and crocus.

There are two ways to go about forcing bulbs. The first way is to cool the bulbs for the required time, then pot them up, place them in a sunny window and water them. This is a space saver for you, but is not always the best choice. 

The second option is to buy the bulbs, plant them in pots, and then cool the pots for the required amount of time.  This method allows for the roots to establish themselves in the soil and generally gives you better results. Bulbs need to be planted in pots that allow for at least two inches of soil under each bulb. This gives the roots space to grow.  Also, to help support the plants as they grow, pack as many bulbs into your pot as possible. Place the bulbs in a single layer, touching the sides of the other bulbs as well as the sides of the pot.

With either option, chilling is a must.  This can be done by placing the bulbs, or pots of bulbs, in a paper bag in the refrigerator. Keep them away from fresh fruits and vegetables, or where they could get wet. If you have an extra refrigerator in your basement or garage, that could be the perfect place for them where they won’t get disturbed—just don’t forget that you put them there! You could also put potted bulbs in an unheated garage or basement, where it will be plenty cold for them, but not freezing. It is better if that room you put them in is dark.  If you choose to pot the bulbs before chilling, be sure to keep the soil damp, but not soaking wet.

As a general rule, you will need to start chilling bulbs in September for blooms in January, October for blooms in February, November for blooms in March, and so on. Here is a more specific list on how long you need to chill various bulbs:

Chilling and Blooming Times

  • Daffodils (Narcissus): 12-15 weeks of chilling
  • Tulips: 10-16 weeks of chilling
  • Crocus: 8-15 weeks of chilling
  • Grape hyacinth (Muscari): 8-15 weeks of chilling 
  • Snowdrop (Galanthus): 15 weeks of chilling
  • Hyacinth: 12-15 weeks of chilling

Depending on which method you used for chilling, potted or not potted, the next step may vary.  If you have already potted the bulbs, all you need to do is keep an eye out for green sprouts. Once the sprouts start to peek through the soil, it is time to move the pot into a warm, sunny room. If you have not yet potted up the bulbs, you will need to do that now, using the same method as discussed earlier. Once they are potted, lightly water the pot until the soil is damp. Put these pots in a warm, sunny window.

When your bulbs begin to bloom, take them out of the direct sunlight to help preserve the blooms. Enjoy the touch of spring during the cold months of winter.

Christian Goers