A How-To Guide to Forcing Bulbs Indoors

A How-To Guide to Forcing Bulbs Indoors

By Michael Jenkins

We’ve written before in this blog about planting bulbs and caring for them, but the truth is we haven’t paid as much attention to them as maybe we should have. Bulb plants—daffodils, tulips, and the like—are much loved by many gardeners and can be some of the first flowers to appear in the spring. After a long winter with record-setting cold temperatures in many places, color and life in the garden is a welcome sight. While waiting for your bulbs to burst forth naturally is one of the fun parts of spring gardening, you can also cheat a bit by forcing bulbs indoors. “Forcing” in this case means getting them to grow and bloom earlier in the year than they would have naturally. It requires very little in the way of special materials; the art of of forcing bulbs indoors is one of timing more than anything else. So for those of you who are new, here’s a how-to guide to forcing bulbs indoors, written as a beginner’s guide for all of us.

A quick note before we start: while this advice applies to many bulbs, some bulbs native to temperate or tropical places don’t require a chilling process, and doing so can actually harm them. Amaryllis and paperwhites are the most common examples; these just need a soak in lukewarm water for a few hours before being planted in good light potting soil with the top half to two-thirds of the bulbs exposed. Place the container in a warm, sunny spot indoors and keep the soil damp.

Forcing bulbs requires us to convince the bulbs that they’ve been through winter and that warmer weather has arrived. If you’re growing bulbs indoors, the easiest way to simulate winter is by giving them some time in the bottom of a refrigerator, an unheated basement or garage, or any other cold but protected space. As with most gardening, some experimentation may be required here and that’s part of the process and part of the fun.

So how long do you need to chill your bulbs? That depends, but here’s a quick rough guide to how long to chill your bulbs in order to best force them indoors:

  • Amaryllis:no chill time needed, blooms generally occur in six to eight weeks after planting
  • Crocus:eight to 15 weeks of chill time; blooms in two to three weeks
  • Daffodil:two to three weeks of chill time, blooms in two to three weeks
  • Hyacinth:eight to 15 weeks of chill time, blooms in two to three weeks
  • Iris:13 to 15 weeks of chill time, blooms in 2-3 weeks
  • Snowdrop:15 weeks of chill time, blooms in two weeks
  • Tulips:10 to 16 weeks of chill time, blooms in two to three weeks.

After chilling your bulbs as needed, the next step is planting. Bulbs indoors or on a patio require containers with good drainage, a light potting soil mix, a warm space with good light. Artificial light is fine for bulbs indoors as long as it’s full-spectrum, so use a good grow light. Moist but not wet conditions are desirable for most bulbs, so a small indoor greenhouse or other container/plant cover can help.  Give bulbs some time to wake up after chilling by planting them in the container with roughly half to two-thirds of the bulb exposed. Keep them in a warm place with some indirect light at first. Once they start to put out growth, move them into more direct light.

Forcing bulbs is an interesting garden experiment, a fun way to bring color indoors in winter, and a way to get a head start on the spring flower garden. We encourage you to give it a try and learn a bit more about how bulbs grow. If you’ve forced bulbs successfully, we’d love to hear your stories so reach out and let us know how it went!

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