Bulbs That Don’t Need Chilling: Is Cold Treatment For Bulbs Necessary

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By Bonnie L. Grant

Few things give back as much as flowering bulbs. They are easy to plant and care for and come in a wondrous array of forms and colors. Planting time is important with bulbs because some require the chilling period of winter to force spring bloom. So, the disorganized gardener will have to rely on summer blooming bulbs if he/she forgot to plant in fall. Here is a little primer on the many wonderful bulbs that don’t need chilling.

Non-chilling Flower Bulbs

Spring blooming bulbs naturally go through a period of chilling during winter, which will cause dormancy. The warmer temperatures of spring force the embryonic plant inside to wake up and begin growing. Summer bloomers don’t require this cold period and tender varieties may even be killed by exposure to cold temperatures. For this reason, many of the bulbs need to be dug up and held indoors in winter to ensure their viability the next season.

There are many types of plants that flower and flourish in summer, but bulbs provide a unique spectrum of form and color that accents the usual perennials and annuals in the flower bed. Summer bulbs are planted in spring after all danger of frost has passed. Spring bulbs need temperatures of at least 40 degrees Fahrenheit (4 C.) to force them out of dormancy, but this isn’t the case with the summer flowering types. Since they are bulbs that don’t need chilling, they are the best bet for a gardener that forgot to plant bulbs in fall.

Which Bulbs Do Not Require Chilling?


Now that we have established that there are two season types of bulbs with different temperature needs, it is time to wonder which bulbs do not require chilling. Some very common non-chilling bulbs are amaryllis and paperwhites. These are commonly grown as houseplants around Christmas and Hanukah but can also be planted outdoors in suitable regions.

Crocosmia is fairly hardy and is a summer bloomer that doesn’t need a cold period. Agapanthus is a stunning and regal blue flowering bulb, while Hymenocallis abounds with large mid-season white flowers. Additional examples of bulbs that don’t need chilling include:

Cold Treatment for Bulbs

If you have your heart set on tulips, narcissicrocus or other early season blooming bulbs, you may need to provide a cold treatment for bulbs to sprout. Summer blooming varieties are good for forcing bulbs without chilling, but the spring types need a cold period followed by warmth to break dormancy.

The method for forcing bulbs without chilling is simply to start them indoors in pots with a good bulb mixture or equal parts soil, peat and perlite. Plant the bulb with the pointed end up and the flatter end at the bottom of the hole. Spring blooming bulbs need little more than a warm location inside and average water.

Spring bloomers require the cold treatment, and forcing bulbs without chilling will result in soggy bulbs in a pot. Most spring bulbs will come pre-chilled, but if you have over wintered them indoors, it is easy to mimic the cold period. Place the bulbs in peat moss and refrigerate them for three months, then bring them out and gradually let the bulbs warm for a couple of days before planting them.

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