Crystals don’t reduce their internal entropy. They grow only on the interface with the media, and the portions of the crystal that become internal during this process do not change after crystallization if kept at constant temp and pressure.

In contrast, if you put a plant and its media (soil, air, water) into constant temp and pressure, the plant will continue to grow and change until it exhausts the media. (assuming the temp and pressure are conducive to life) Ultimately plants become their own media by decomposing into soil.