How to Force Hyacinth Bulbs

Dutch hyacinths are some of the world’s most fragrant flowers. They are a wonderful addition to any spring garden and are also one of the best bulbs for “forcing”. Forcing is a planting technique that lets you bring plants into bloom weeks or even months before they would normally flower in your garden. Read on for easy, step-by-step instructions.

HYACINTH BULBS NEED TO BE PRE-CHILLED

As with most other spring-blooming bulbs, hyacinths need to go through a period of cold weather (35-48°F) in order to bloom properly. Being exposed to wintery temperatures tells the embryonic flower inside the bulb that spring is coming and flower development should begin. If the bulbs are not exposed to the right amount of cold for the right amount of time, the flowers will not form properly and may not emerge at all.

HOW TO CHILL YOUR BULBS

It’s possible to purchase pre-chilled hyacinth bulbs, but they’re not always easy to find. Chilling your own bulbs gives you more control over bloom time and also gives you many more choices for varieties.You can chill your hyacinth bulbs either before or after you plant them. In both cases, the chilling period needs to last at least 13 weeks. During this time the bulbs need:

Darkness
Moist soil or humid air
Consistent temperatures of 35 to 48°F

WHERE TO CHILL YOUR BULBS

In growing zones 7 and 8, winter temperatures may be cold enough to chill the bulbs outdoors. In zones 3-6, you need to protect the bulbs from the extreme cold so they don’t freeze. Consider using an unheated basement, an attached garage or porch, or a greenhouse or cold frame.Another option is to chill the bulbs (planted or unplanted) in a refrigerator. Just make sure not to store any fruit in there at the same time. The ethylene gas given off by ripening fruit will damage the embryonic flowers inside the bulbs.

WHEN TO PLANT HYACINTH BULBS

It’s difficult to know exactly when forced bulbs will bloom. For a continuous parade of spring color, choose several different varieties of hyacinths and plant a few bulbs each week between mid-October and mid-November. Bulbs planted in mid-October will bloom in February. Bulbs planted in mid-November will typically bloom in March and April.

HOW TO PLANT THE BULBS

You can combine hyacinths, tulips, daffodils, crocus and other bulbs in the same pot, but you’ll get better results if you plant just one type of bulb per pot.Hyacinths look best in a shallow, 4 to 6” deep container. Make sure there’s a drainage hole on the bottom of the pot, and use a high quality growing mix to encourage strong root development.Pour some of the growing mix into a bucket and add warm water. Mix it around with your hands until it is completely moistened, but not soggy. Put 2 to 3” inches of the mix in the bottom of the container and set the bulbs on top, pointy-end up. Hyacinths look best when the bulbs are positioned about 1” apart. Cover them with more soil, until the tips are about an inch below the soil surface. Label each pot so you know what’s in it, and water thoroughly to settle the bulbs in place.Keep the bulbs in the dark, and keep the soil lightly moist during the entire 13 to 16-week chilling period.

FORCING HYACINTHS IN WATER

Hyacinths can also be grown without any soil. A forcing vase is designed especially for this purpose. It has a wide base to contain the water and roots, and a narrow neck to hold the bulb so it doesn’t quite touch the water.Remember that all hyacinths bulbs need to be pre-chilled. When using a forcing vase, you can chill the bulbs separately and then put them in the vase, or put them in the vase and then chill them.

TIPS FOR BLOOM TIME

By the time the chilling period ends, your bulbs may have started to sprout. If you want to hold them back a few weeks, just keep the pots cool and dark. When the sprouts are 2” tall, move the pots or forcing vases to a cool window with indirect light. When the buds begin to show color, move the plants to a sunny window.Once the flowers are open, keep the pots or vases in a relatively cool location out of direct sunlight to extend the bloom time. If you want to arrange your hyacinths in a vase, feel free cut the stems just as you would do outdoors.

HOW TO CARE FOR THE BULBS AFTER THEY BLOOM

When planted in a garden, hyacinth bulbs will usually rebloom for 2 or 3 years. Forced bulbs are usually treated as annuals and discarded after they flower.To learn about planting spring-blooming bulbs in containers for outdoor display, read: How to Grow Spring Bulbs in Containers.

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