Broad leaf trees get all the glory come fall. Their dazzling colors put on a display for a few weeks every year that is unrivaled. However, it isn't just broad leaf trees that are preparing for winter in this manner. There are some conifers doing the same. The handful that have evolved this deciduous strategy are just as dazzling as their broad leaf neighbors.

The most famous of these are the larches (genus Larix), however, there are others such as baldcypress (genus Taxodium) and the dawn redwoods (genus Metasequoia). So, why have these conifers evolved to be deciduous? There are likely many reasons these genera utilize this strategy but it most likely comes down to cost versus benefit. Needles that last for years are costly to make despite their advantages. They are no guarantee of success either, especially for the larches, which often grow in areas that experience some of the harshest winters on the planet. Heavy snow pack and deep winter chills can take their toll on conifers and many evergreen species show signs of frost damage and broken limbs from snow loads. The habitats in which deciduous conifers are found can be tough places to eek out a living.

By shedding their needles, the larches can get around these issues a bit. They also tend to grow in swampy areas where getting the nutrients needed for survival can be extra difficult. By producing relatively weak needles that are easily replaced from year to year, trees like larches and cypress may get around having to waste resources on more robust needles. Finally, it should be noted that this strategy is by no means less efficient. These genera do quite fine with their deciduous nature. For the most part, these trees are nonetheless successful and can live for centuries. It is mysteries like these that keep the wonderful world of botany interesting.

Further Reading:
http://www.metla.fi/silvafennica/full/sf36/sf363703.pdf