Bulbs – When to Plant in fall

Spring-flowering bulbs have been on garden center shelves for weeks but the real season for planting them begins in late October.  My preference is to wait to plant daffodil, tulip, hyacinth, Dutch iris, etc. until night temperatures are consistently below 60 degrees. At that time the soil is warm enough to stimulate root growth but you won’t get much foliage growth. You can successfully plant them as late as December but the later you wait after October the less able the bulbs will be to establish themselves.

If you cannot plant the bulbs right away, store them at around 60-65 degrees F in a dry area. Temperatures above 70 degrees F may damage the flower buds. In areas of the state with extremely mild winter climates, it may be desirable to pre-cool some bulbs. Most spring-flowering bulbs require a 12-16 week cold period in ventilated packages in the bottom of your refrigerator at 40-50 degrees F before planting. Check with your bulb supplier to determine whether the bulbs you purchase have been pre-cooled or whether you may need to give them a cold treatment.

Planting depth isn’t critical. Spring-flowering bulbs usually do fine if the top of the bulb is covered by a couple of inches of soil.  Mulches or ground covers may be necessary to ensure winter survival of some bulbs. They not only minimize winter injury, but also provide a background against which little bulbs show to better advantage. Mulch also prevents mud-spattering from heavy rains that frequently spoil the flowers. Pine straw, bark, fall leaves, and many other organic materials make satisfactory mulches for bulbs.

There is no effective means of providing cold protection once the plant is in bloom. While late or severe cold waves occasionally spoil spring-flowering bulbs, the bulbs are amazingly resilient and many withstand severe cold.

A well-prepared bed should require little cultivation except periodic weeding. Many spring-flowering bulbs are “overplanted” with other plants, frequently annuals. Be sure not to dig so deeply as to damage the bulbs. When the flowers fade, cut them off to prevent seed formation. It is best not to cut or remove the foliage until it dies naturally. Most spring-flowering bulbs produce foliage in fall or early spring that dies by late spring or early summer.

Normal rainfall usually provides enough moisture for spring-flowering bulbs. Eventually almost all bulbs become overcrowded and must be divided and replanted for best effect. The length of time depends largely on the bulb’s ability to produce bulblets. Some may remain undisturbed for many years while others may require dividing every two to three years. Do not dig bulbs until the foliage has turned yellow and withers. Be cautious when digging so as not to damage the bulbs.

There are two critical times to feed your bulbs. They need nutrients in the fall when they are planted and they need more in the spring when they have leaves. For every ten square feet of bed sprinkle two cups of 10-10-10 fertilizer over the soil and dig it in as you prepare an area for planting. Use the same amount next March when the leaves emerge.

If deer or rabbits are a problem in your area, select bulbs such as daffodils, Siberian squill, and fritillaria.  It’s easy to fall in love with the daffodil ‘Thalia’, so it’s no wonder this outstanding heirloom from 1916 is still popular today. Graced by lovely pure-white flowers and a sensuous fragrance, ‘Thalia’ reliably comes back year after year. Plus, even the hungriest deer and rabbits pass it by in search of tastier treats. In addition, it’s a great cut flower.

“What can’t you say about Siberian squill?” It’s supereasy to grow, spreads over time, and displays true-blue color.  A great choice for mixing in the lawn for a dose of early-spring interest, Siberian squill even thrives in shade. It’s truly a plant-it-and-forget-it bulb. Fritillaria imperialis is probably the most surprising-looking spring flower you will ever run across. Each plant has a single, strong stalk, topped by large, hanging blossoms, which are crowned by a fringe of leaves. The fringe on top is said to resemble a crown; it is for this reason that the common name for Fritillaria imperialis is “Crown Imperial”.

Brenda Larson is Horticulture Agent for North Carolina Cooperative Extension in Lee County.

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