Crop Vignette: Bulb and Corm Crops

This article first appeared as “Spotlight on Ornamentals: Time to Think Spring!” in IR-4 Newsletter 44(3):5

Plant Information

Crocus and other early spring flowers are the harbingers of warmer days after a cold winter. Easter lilies and hyacinths commonly are given to celebrate the spring holidays. Daffodils, tulips and Frittilaria brighten up an otherwise dull border before spring annuals and early flowering perennials. Iris, Crocosomia, daylilies and gladiolus often are great companion plants for rose, lavender, hosta or other perennials. What do most of these flowers have in common? They are grown from bulbs or corms and usually need to be planted in the fall for bloom the following spring or summer in commercial and residential landscapes. Many will return year after year if they are planted in a suitable location allowing them to overwinter and receive enough chilling to induce flowering.

In addition to landscape settings, bulb or corm crops can be forced to flower by simulating overwintering conditions and providing the chilling requirement. Often this will lead to flowering potted bulbs as temporary houseplants in winter months, such as Amaryllis during winter holidays or grape hyacinth paired with crocus to brighten the day in late January or February.

U.S. growers produce $48.5 million bulbs and corms annually and propagative materials (USDA-NASS, Census of Horticulture, 2009). In other words, domestic production includes bulbs and corms for commercial and domestic landscapes as well as for specialty forced bulbs and for cut flowers. Gladiolus, lilies and freesia are commonly placed in floral arrangements, but many other bulb crops are found in these special occasion arrangements.

Main Disease Problems

Bulb and corm crops are prone to disease and pests and in field production weed management is key to optimal crop production. The search for methyl bromide alternatives has been an important avenue of research to minimize initial weed seed and disease inoculum for field grown bulbs. Disease issues include bulb and corm rots and root rots caused by FusariumRhizoctonia and Pythium and foliar diseases such as Botrytis and downy mildews. Viruses and bacteria can plague production systems. Nematodes and arthropod pests often cause economic damage in addition to vectoring viral diseases. For more information about bulb crops, please consult ‘Ornamental Geophytes: from Basic Science to Sustainable Horticulture Production’ by Rina Kamentsky and Hiroshi Okubo.

IR-4 Research

To aid growers, IR-4 has screened bactericides, fungicides, insecticides and herbicides for crop safety on a number of bulb and corm crops including daffodil, iris and tulip. In addition, IR-4 has screened products for Fusarium on gladiolus and facilitated research on the invasive pathogen gladiolus rust.


Helpful Growing Tips from American Meadows

How to Plant Fall Flower Bulbs

Fall bulbs are loved by both beginner and master gardeners, there are so few issues to consider. Gardeners can put all their effort into the fun part of gardening – design.

Fall allows a “second season” of planting for spring blooming bulbs. Planting in the fall allows a jump start to spring growth. The cool weather helps to make a more enjoyable experience for working outside in the garden and requires less watering. The cooler weather allows spring blooming bulbs to winter over, this is important in order for bulbs to provide beautiful spring cheerful blooms.

When bulbs arrive: Bulbs should be planted as soon as the group is cool, when evening temperatures average between 40 to 50 degrees Fahrenheit. You should plant at least 6-8 weeks before the ground freezes. This is most common in cold climates (zones 1-7). You can, if necessary, store bulbs for a month or longer, if you keep them in a cool dry place. Planting fall bulbs in warm climates (zones 8-11) such as Tulips, Daffodils, Crocus, Hyacinths, Scilla and Snowdrops, require pre-chilling in order to bloom. To pre-chill, leave bulbs in their bags and place in a refrigerator for 6-10 weeks. Be careful not to store bulbs near fruit, especially apples, all ripening fruit give off ethylene gas which can damage and kill the flower inside the bulb. Once bulbs are chilled, plant them at the coolest time of the year. Most importantly, bulbs won’t last till next season, so make sure to plant them.

Read the Label: Try to keep the label together with the bulbs until planting. Without the label, you cannot tell the red tulips from the white tulips just by looking at the bulbs.

Where to Plant: You can plant bulbs just about anywhere in your garden as long as the soil drains well. The Dutch say “bulbs don’t like wet feet.” So, avoid areas where water collects, such as the bottom of hills. Bulbs like the sun and enjoy areas in the spring garden that can be very sunny, since the leaves on the trees are not out yet. So keep in mind when planting in the fall that you can plant in many places for spring blooms.

Prepare the Planting Bed: Dig soil so it’s loose and workable. If it’s not an established garden bed, chances are the soil could use the addition of some organic matter such as compost or peat moss. These are available at most local garden retailers.

Sources Cited