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Time to Plant Spring Bulbs

This article was originally published on September 22, 2009 and expired on September 30, 2009. It is provided here for archival purposes and may contain dated information.

September doesn't seem like the time to be thinking about your spring garden, but when it comes to hardy spring-blooming bulbs, fall is the right time. We purchase and plant tulips, daffodils, crocus and many other bulbs as the days get shorter and our night temperatures start to dip into the 50s. For Illinois, this is usually about mid-October.

When you buy a spring-blooming bulb in the fall, it is basically dormant, explains Martha Smith, University of Illinois Extension horticulture educator. There are internal activities going on, but the bulb seems to not be growing. When we plant the bulb, it begins to grow, developing roots and elongating its flower stalk. This stage is important to prepare the bulb for its spring debut. The bulb senses colder temperatures and stops growing. For spring-blooming bulbs to flower correctly, they need a cold resting period called vernalization. For spring bulbs in Illinois, this is called winter. Each variety has its own internal time clock regarding how long it needs to be in this cold resting state. Early blooming bulbs have a shorter time period than late spring-blooming bulbs.

When selecting bulbs, pay attention to flowering times and where you will be planting them in your garden. Combine early-, mid-, and late-blooming bulbs for a fantastic display from early March through late May. Select a site that does not hold water or stay wet at any time during the year.

Bulbs are modified underground storage organs. What they store is primarily food needed to support the above-ground plant until it can produce its own through photosynthesis. Once the above-ground portion starts to die down, food is being sent back to the bulb to reform for next year.

Think of an onion in your pantry… that is a type of bulb. If it gets too wet, it will rot. If your bulbs are in a low-lying area where snow melt drains, they will rot.

Do these bulbs need full sun or partial shade? Plant according to sun requirements.

Smith says to plant bulbs two to three times as deep as the bulb is tall. For most tulips and daffodils, plant them 6 to 8 inches deep, measuring from the bottom of the bulb to the soil surface. Phosphorous is needed to encourage root development and moves very little in the soil. Mix the recommended amount of phosphorous in the soil below where you will place the bulb. Read and follow product quantity instructions. Dig your planting hole or area, spread phosphorous, and stir into the soil. Place bulbs and follow with 5 tablespoons of 10-10-10 soluble fertilizer mixed into the soil that will be placed over the bulb. When soil temperatures warm in the spring, the bulbs will start to grow.

For more tips and ideas, download our flowering bulb fact sheets at http://web.extension.uiuc.edu/regions/hort.

Source: Martha A. Smith, Extension Educator, Horticulture, smithma@illinois.edu

Pull date: September 30, 2009

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