In Chinese Medicine Spring is related to the Wood element. The nature of Wood is expansive. It pushes upwards and outwards. You can imagine seeds growing upwards out of the ground towards the light and warmth. The Wood Element encompasses all forms of vegetation from grasses and flowers to trees. The Power of Wood is birth. Spring time is also lambing time. Many animals give birth to their young in Spring time. The Wood element relates to the Liver and Gall Bladder. In terms of Chinese Medicine the Liver is the General that makes the plans and the Gall Bladder is the decision maker. The spirit of the Liver is the Hun. This represents the spiritual aspect of the Liver Meridian. It is involved with thinking, sleeping and consciousness. It is easily upset by drugs and alcohol. When a person uses "astral travel" it is their Hun that leaves their body.
The Wood Element
References
Hicks, Hicks and Mole, 2004, Five Element Constitutional Acupuncture, Churchill Livingstone