Forcing Bulbs

force spring bulbs crocus in February

By Jane Schildroth, Linn County Extension & Outreach Master Gardener

I have planted three little groupings of crocus bulbs in just the right spot in my garden.  It will be fun to see the color pop up in the spring along with the other spring surprises.  Now, I’m getting greedy.  This is the year I’m definitely going to try and force some of those crocus bulbs to bloom in February.  It doesn’t seem to be difficult – the hardest part is going to be finding room in the fridge!

Even though I am experimenting with crocuses, it’s also possible to use daffodils, hyacinths, tulips and Paperwhite Narcissus.  The latter produces an aroma I’ve enjoyed for many years when the holidays are over and the house needs perking up.  For varieties of bulbs recommended for forcing, see Forcing Flower Bulbs. Avoid cheap or obviously damaged bulbs to avoid disappointment.

Choose a container with drainage holes and one that is twice as deep as the bulbs you want to plant.  This means for my crocus bulbs, I don’t need a very deep pot.  I will use a commercial potting soil and partially fill my containers.  I want enough soil so the bulb tips will be even with the rim of the pot.  In a pot that is 6 inches in diameter, I can use 10-12 crocus bulbs.  Three hyacinths, 3-5 daffodils or 5-7 tulips will also fit.  Next, fill in with more potting soil until the tips of the bulbs show just above the surface of the soil.  Water from the top or partially submerge the pot in a tub of water until the surface is moist.

When you have planted your bulbs, place the pots in a cool cellar or a refrigerator for 12-16 weeks.  They need this cold period to bloom properly.  Put the pots in a plastic bag if you will be storing them in your fridge.  This will protect the bulbs from fruit, such as apples, which give off a gas that can ruin this experiment.  Once a month, the pots also need to be brought out, watered and left for 1-2 hours with the bag open so the bulbs have a chance to exchange air.  After this time has passed, re-seal your plastic bag and put it back in place.

You’ll know the bulbs have developed properly after 12 weeks in cold storage if there are roots visible through the drainage holes and if yellow shoots are showing from the bulbs.  At this point, place your containers in a location that is 50-60 degrees with low to medium light.  When the shoots turn green, move them to a brightly-lighted and warmer spot.  In 3-4 weeks from their removal from cold storage, the bulbs will flower.  Enjoy your blooms – but act now to make it happen!

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