DIY: How to Force Bulbs in the Winter. A Thoughtful and Affordable Gift!

Hey it’s Caroline, your horticulture coach! Today I’m writing to teach you how to easily grow magnificent spring flowers in the dead of winter. These affordable and thoughtful gifts are great for Hanukkah, Christmas, Valentine’s Day or whatever!

11182216_10155540350055383_1344613156235801015_nTo initiate flower buds, many herbaceous perennial plants require to be exposed to a specific number of days with minimum temperatures. This cold resting period is called “vernalization.” Forcing is the process of providing artificial vernalization. Blooms don’t fully develop if winters are too mild, resulting in bad crop yields and stunted plants. This stress can kill the plant, and is a critical problem with the progression of climate change. (Sorry to be a Debbie Downer, but it’s a fact.) Many seeds also need a cold period to germinate. This is called stratifcation.

It generally takes about 12 to 16 weeks to force tulips and hyacinths. So now is the perfect time to prepare them in the fridge for beautiful, fragrant blooms in late winter! Say goodbye to winter blues and hello to an early spring!


For this DIY you will need:

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A good tulip bulb has an intact skin, or “tunic.”
  1. Spring Bulbs and Corms: I got a little crazy and bought my bulbs without researching… Thankfully just about any spring bulb can be easily forced; except Allium, Camassia, Scilla campanulata, and lilies which are more difficult. The great thing about forcing bulbs is that you can grow plants that aren’t hardy in your climate zone. They can also be mixed together to create detailed arrangements.

When choosing bulbs, avoid buying ones that have already sprouted, are damaged, soft, or smaller than others.  For my first time trying this at home, I chose “Angelique” and “Freeman” tulip cultivars and a mix of Iris.

2. A 32 degrees to 50 degrees F dark area: I used a refrigerator, but garages and basements work well too.

3. Stones or Potting Soil: Aquarium and glass stones work well. If you want to use potting soil, it’s important that it be well draining. A potting soil that is one part sphagnum peat moss to one part vermiculite or perlite should do the trick.

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4. Glass Container or Pot: If you’re using rocks, any glass container will do. If you’re using potting soil, make sure the container has drainage holes. A standard 6 inch pot allows enough room for at least 3 daffodils and up to 5 or 6 tulip bulbs. Pots can be shallow because bulbs only need 1 inch of soil underneath them.

You also may need:

The bulb should never be touching water directly when being forced. You can buy special bulb forcing vases, or just use tape to keep bulbs in place above the water. Soon there will be roots growing into the water below!
The bulb should never be touching water directly when being forced. You can buy special bulb forcing vases, or just use tape to keep bulbs in place above the water. Soon there will be roots growing into the water below!
  • Tape
  • Water polymer (crystal gel or water beads): I decided to try to force some of my bulbs in a superabsorbant polymer called “crystal ice.” If it works, it’ll be a cheaper and attractive alternative to stones. I had so much fun playing with it.
  • A strainer was also helpful to strain the polymer from water.

Let’s Get Started!

If you can’t plant your bulbs right away, store them in the refrigerator. Keep them away from fruit, especially apples, because the ethylene gas they produce inhibits flowering and causes flower abortion.

Planting with soil:

  1. Fill the pot with 1 inch of soil.
  2. Place the bulbs with the tip pointed up. Bulbs can be spaced about 1 inch apart in pots. (As opposed to 2-3 widths of the bulb, when spacing in the ground.) If your bulb has a flat side, position that side to be facing outwards. This will allow the leaves to grow outwards. There is no need to compress the soil, it causes inhibition of root growth.
  3. Cover small bulbs completely. Larger bulbs, like tulips and daffodils, can have their tips poking out of the soil. When filling the pot, allow about 1 cm of “head space” below the rim of the pot. This will prevent overflow when watering.
  4. Keep soil moist, but not wet.

DSC01600Planting with Rocks or Water Polymer:

  1. Fill the container with a few inches of rocks or (saturated) water polymer. It’s better to have a good volume of rocks, so you won’t have to water as often.
  2. Fill the container with water, so that the surface of the rocks is just above the water level.
  3. Place the bulbs 1 inch apart from each other, with tips pointed up. Bulbs should never be touching water, to prevent rot.
  4. Maintain the water level so that it’s just below, but not touching, the bulb.

After Planting:

4. Place containers in a 32 degrees to 50 degrees F dark area.

5. The vernalization (cold) period may be different for different cultivars and species. If the length of time isn’t on the packaging google it.  It generally takes about 12 to 16 weeks to force tulips. Late blooming bulbs will require more time.

6. When shoots and roots are visible, move containers into a cool room (between 50-55° F) out of direct sunlight.

7. Once shoots turn green, move them into direct light and warmer conditions of 60° F. (I don’t have rooms this cool, so I’m just going to do the best I can.)

8. It will take between 2 – 3 weeks to flower. During this time keep soil moist, or maintain the water level.

9. Once flower buds start to form, the plants can be moved out of direct light and into bright indirect light. This will help to prolong the bloom period.

Other tips:

  • If you’re aiming for a specific date, flowering can be delayed by moving the plants into a cool room (40 to 50° F) out with indirect sunlight. To start growing again, bring plants gradually back into sunlight and warmth.
  • Flowers last longer if the they’re moved into a cool room (40 to 50° F) at night.
  • Bulbs cannot be forced two years in a row. After bloom, the bulbs can be added to your garden for many more years of flowers.
  • Don’t add fertilizer. The flower grows from stored energy in the bulb.

Forced Bulb Vlog!


If all goes well, they’ll be blooming in January and I’ll do a follow up post! I’m so excited!

Thank you for watching and/or reading!

Let me know your thoughts, and how it works for you in the comments.

Like, share, skubscribe!


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For more on forcing bulbs visit:

http://www.weekendgardener.net/flower-bulbs/forcing-120712.htm

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2 thoughts on “DIY: How to Force Bulbs in the Winter. A Thoughtful and Affordable Gift!

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