Gardening: Forcing hyacinths requires 10 to 13 weeks of cold, darkness

For the News-DemocratDecember 12, 2013 

Q. I have two dozen hyacinth bulbs for forcing with special hyacinth glasses for growing the bulbs. Could you give the correct directions on how I should proceed? I have always placed them about 1/2 of an inch above the water. Should they be placed in a sunny window? I have good luck planting them outside after blooming on a warm day. I do want to provide some directions when I give these, tied to the glasses, to friends.

-- B. T. of Belleville

A. All hardy spring flowering bulbs require a period of cold treatment of 35 to 45 degrees in a dark location for 10 to 13 weeks to condition the bulbs to form roots and initiate floral buds. You can pay extra for bulbs that have been pre-chilled for just three or four weeks. You will still have to extend the cold period for another 7 to 10 weeks.

You could do this in a refrigerator, but keep the bulbs away from the crisper drawers that hold vegetables and fruit. These can release ethylene gas, which will stop bulb development.

Or you can place them in a cold frame once the soil temperatures begin to drop; again for a minimum of 10 weeks. You can cover these with leaves and top with a wire fence or slats to keep the leaves from blowing away.

After this cold treatment, place the bulbs in the hyacinth glasses just so the roots are in the water below the indentation of the sides of the glasses. If you add too much water above the indentation, the bulbs will rot. Place the bulbs and glasses in a cool location with no light at all or very little light but no sunlight of any duration for a week or two. As the floral buds begin to emerge from the bulb, gradually move these bulbs to brighter light conditions but bring the temperature up slowly. Avoid direct sunlight as this will speed up the flower development and make it end in a short time.

Then, as you already know, you can plant the bulbs outside once the bloom period is over. It will require another cold treatment to produce floral buds. You may want to add a 5-10-5 or a 6-10-4 fertilizer at the rate of 2pounds per 100 square feet. Make sure the fertilizer is below the bulb so the bulb will not come into contact with fertilizer pellets.

Q. My friends and I have been discussing snow and freezing temperatures in relationship to controlling insects. Does a layer of snow prevent freezing temperatures from going deeper into the soil?

-- B. K. of Collinsville

A. The deeper the layer of snow, the better the soil is insulated from the colder air. You may be surprised to find out just the cold weather of this past week froze only the top 1/2 inch or, at most, an inch. To control and kill insect pests, you want very cold temperatures around zero or below without any snow on the surface of the soil.

This could freeze the soil down to 6 or 7 inches. As a number of farmers and gardeners know, we have not experienced any unusual cold conditions for the last few winters to kill the larval stages of overwintering insects. As result, their numbers have built up very early in spring.

If you would have tilled the garden in late November or early December, you could have pulled some of these insects higher closer to the soil surface and killed a lot of insects as the cold came quickly this year.

Charles Giedeman is a local contributing writer. Send your gardening questions to Lifestyle Editor Pat Kuhl, Belleville News-Democrat, P.O. Box 427, 120 S. Illinois St., Belleville, IL 62222-0427. Or email to

Do it now

FISH PONDS: Do not use a heater to keep the water warmer as an electrical stoppage can result with dead fish.

Do not feed the fish now. They will feed but their digestive organs slow down with the lower temperatures and the food will rot in their gut, killing the fish.

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