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by Pernell Gerver

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"Forcing Bulbs for Indoor Winter Blooms"

potted crocusNow is the time to pot up bulbs for bloom indoors in the middle of winter. It's a fun, easy project to pot up some bulbs which will be in full bloom providing a touch of spring indoors in January, February, and March - in bloom months ahead of bulbs planted in the garden.

This technique is called "indoor forcing" and it makes it possible to create your own colorful pots of tulips, hyacinths, daffodils, crocus, and other spring-blooming bulbs indoors while it's still winter outdoors. Forcing pots of bulbs is a method of tricking the bulbs into bloom by giving them a cold treatment.

Forcing bulbs is a step-by-step process. The first step is to pot up the bulbs into special pots called bulb pans. A bulb pan is half as deep as it is wide.

potted daffodilsThe next step is to fill the pot with potting mix for bulbs. I make my own special potting mix for forcing bulbs. It has excellent drainage so the bulbs don't rot. Put the potting mix up to the first rim of the bulb pan.

Set the bulbs so that they are spaced equally. The bulbs can even touch each other so you can put many in each bulb pan.

Next, add more potting mix up to one-half inch from the top of the bulb pan. Then give the pot a thorough watering.

The next step is the actual forcing process. The pots of bulbs need to be placed in a cool, dark location for a minimum of 12 weeks. The forcing location needs to have consistently cool temperatures. Temperatures need to be below 50 degrees, but above 32 degrees at all times. Possible forcing locations might be an unheated garage, a cool basement, or an outdoor coldframe as long as the temperature range is appropriate. I like to force potted bulbs in the refrigerator since the temperature is ideal for forcing.

potted tulipsEvery now and then check the pots for watering and water as needed to keep the potting mix moist, but not wet, during forcing.

When you've started the forcing process mark your calendar for 12 weeks so you'll know when to take the potted bulbs out of the cold treatment. Some bulbs will have shoots visible.

After the 12-week cold treatment, the next step is to move the potted bulbs to a partially-dark location indoors at around 60 degrees. After a few days move the pots to a bright window in a cool room (or a cool greenhouse if you have one) away from heaters or drafts.

The pots of bulbs will begin sending out leaves then flowers. For the longest-possible bloom, keep the potted bulbs in the coolest room of the house.

Pernell Gerver's Gardening Q & Aby Pernell Gerver

"Certain Bulbs Need to Be Dug Up for Winter"


Q. What bulbs need to be taken out for winter? Thanks!

A. Bulbs that should be dug up and stored indoors for winter include dahlia, gladiolus, canna, acidanthera, pineapple lily, tuberous begonia, agapanthus, sprekelia, Siam tulip, elephant's ear, and caladium. Not all grow from bulbs; some grow from a tuber or a rhizome, but all are tender and would not survive the winter if left in the ground. Here's a tip to keep the bulbs from shriveling up in storage over winter. Spray the bulbs with Antidesiccant before storing them in a cool, dark location indoors. The Antidesiccant seals in moisture. I've had 100% success with keeping tender bulbs from year to year by spraying them with Antidesiccant before storage.

Click here to read more about Antidesiccant and order it from Pernell Gerver's Online Store.

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