Actually what happens is during a mild winter, the soil stays too warm and the bulbs begin to come out of dormancy early. They start to grow, and once the tips emerge above the soil line, they are subject to freezing if the temperatures dip back down below freezing. And that's usually what happens. After the bulbs have emerged, they freeze and then don't bloom at all, or if they do it's a very sad display.

Another reason this happens is because the bulbs are not planted deep enough. They may have been deep enough when you planted them, but as the soil goes through the freezing and thawing process, the bulbs can actually work their way up in the ground. One way to keep your flower bulbs sleeping longer, which will protect them from freezing, is to mulch the bed.

In the fall just apply a 3-4" layer of well composted mulch. This layer of mulch will do a couple of things. It will maintain a higher moisture content in the soil, which is good as long as the soil isn't too soggy. Well composted mulch also adds valuable organic matter to the planting bed. Organic matter makes a great natural fertilizer.

A 3-4" layer of mulch also acts as an insulator. It will keep the soil from freezing for a while, which is good because you don't want the bulbs going through a series of short cycles of freezing and thawing. Then when the temperatures drop below freezing and stay there for a while, the soil does eventually freeze. Then the mulch actually works in reverse and keeps the soil from thawing out too early. Keeping it in a frozen state is actually good because the bulbs remain dormant for a longer period of time.

When they finally do wake up it is spring time, and hopefully by the time they emerge from the ground the danger of a hard freeze is past and they will not be damaged. If you can keep them from freezing, they will flower beautifully. The extra organic matter will help to nourish the bulbs when they are done blooming, and the cycle starts all over again.

We also plant annual flowers in the same beds with our spring bulbs. By the time the danger of frost is past and it's time to plant the annuals, the top of the bulbs have died back and are ready to be removed. The mulch that is added in the fall also helps to nourish the annual flowers, as well as improve the soil permanently. Any time you add well composted organic matter to your planting beds, you are bound to realize multiple benefits. The key words here are "well composted". Fresh material is not good.