chelle said:As long as the bulbs are hardy for your area, most will be just fine outdoors in a container. They can freeze solid.
There is a whole lot more to this than meets the eye. Thinking of exposed container growing over the winter as needing to tolerate a full climate zone colder than your area would be more accurate, but still not the end all.
Most spring bulbs* sold are cold hardy to zone 4(or colder), so for chelle and others in zone 5 or warmer, her statement probably holds true for the most part. But as a blanket statement for everywhere (including colder regions), not so.
For cold hardy bulbs, there is a huge difference between below 32F and frozen. In other words, just because the temperature is below 32F does not automatically mean the bulb is frozen. Spring bulbs will not freeze at 31F. (Remember, water freezes at 32F, but other substances and mixtures have their own unique temperatures at which freezing occurs.**) If a person thinks of a bulb as one homogeneous solid mass, pardon my bluntness, but he are wrong. All spring bulbs are composed of parts that can freeze over the winter without damage, and parts that cannot. These parts that cannot freeze have a much lower freezing temperature due to various anti-freezing techniques. Thus, freezing does not occur until somewhere below 0-25F, depending on the species. If the parts that should not freeze actually do, this is where death from freezing occurs.
*Spring bulbs are planted in the fall for spring bloom. Summer bulbs are planted in the spring for summer bloom.
**For instance, when you salt your icy sidewalk, the ice melts even though the temperature remains the same. This is because the new melting point of the new mixture of salt and water is now lower than the ambient temperature.
