Plant a tree and watch it grow
Python

I took a little liberty with this:


I allow multiple trees
Fruit is preceded by flower -- once a flower has 1 food, it turns into a fruit.
Fruit turns ripe when it has 3 food.  It then falls off of the tree, and turns back into a flower.
If fruit falls at least 4 places from any given trunk, it buds into a new tree.  Since it doesn't get much light, I seed it with as much food as was in the fruit.


Sample Output, 2 trees

                            / 
     \/\_ |  /             |  
 _  _/\|\|_\/             /|/ 
  |/ \/|/|O/              \|/ 
   \_/O|@|/               /|_ 
     \_|_|                \|  
_______|___________________|__

                       _      \                                   
                _/ _ \/\___/\|/                  \                
             /|\|\O@|/\/|__\/ \__/_\|/\\|  _ |/| _||/\\ /         
             \|_|@|\|@/O|@@/O_/@O|@/ \//\   \|\||@||@///          
           \_ \_|\|/@\\O|@||/OO//O\\O/ \@|@\||/@|\/\/|/   | / _   
        ___/    |/|/O//O|O||\\/|/O// \_O\|__| \O|/\/O|   _/\\|    
         / \_O@@_\/\O\\@|/O|/O\@\O\\@/OO/|O_@O/O|\/\/     \//|/__ 
     _|/|_|  \\|O\\/O/O||_@|\O|\/O//|O|@\|/O_O\@|/O/\_@O__//_||   
    | \\|____// |O|\O\O|/\@|/ |/O/ \|O|OO|\/@_/O|_O\/O//O_//O/    
    |_O\\@O\/\\OO\|/|/\O\O\|__@\|O@/|/O|O|/\OO\/|_O/  \\|OO\/     
   /  \\||_|\|||_O|\|@/OO\//OOO/|/@\|OO|\|\@|O \|\|O@O//  \/\     
 _/\_/@\|\@|/  \_||/ \\@|/\\\||/ \//O|O|/|/@|\@/|/O/OO\\__/  \||/ 
  \||/  |_|O\__@ |O\O/O||\///@|O_//|/OO|@|OO|/O\|O/OO|// /|\|/\|  
   ||___O@|_/  |__\/||_||/|\\/OO/|@|O|/ \|_O||_/O/O/O|/_|\/\|_/   
    \_OO\\_O\@_|/|_\|_O|/\|//\/|/@|O\|@_O|O_O\/||\/O/|/_|/|O|     
      \_|\@\@|_|\|OO|O|/\//O\/\O\@|_/|_@\|/\O/\||/\|/|@@|@|/      
       /|//|\|O|_|O\O\O\/|O\/|@|/_|\OO@\/ \/|O/_|O//@|@/\_|       
       \O\\|/|_OO|OO\O|/\|@@\|O|/ @//|_@\_/\|//O_/|O/  \/         
        \O\|O_/|/ \|O|O\/|/OO|O|O_/ \|    \/|/|/@ |/\__/          
         |O|_O\|\O/|_|O/\|\//|/   \_/     /\@\| \_/\/             
          \OO\O|/ \ _|@\/O||@|\___/       \/|/    \/              
           |__|O\__|OO\/\@||/\/            \|O____/               
              |____|/@/\|\|O\/            _/|/O                   
                   |/ \/|/|@/              \|/                    
                    \_/O|@|/              |/|__                   
            \|/       \_|_|  \|_      \|/  \|    \|/  _|_         
_____________|__________|_____|________|____|_____|____|__________


Source

from random import choice, shuffle
format = '_\|/_@O'
directions = [(-1,0),(-1,1),(0,1),(1,1),(1,0)]
placement = [[[],[0,1,2],[]],[[],[0,1,2],[3]],[[0,1],[2],[3,4]],[[1],[2,3,4],[]],[[],[2,3,4],[]]]

def shine():
    for x in ymax:
        light = 2.
        for y in range(ymax[x],-1,-1):
            if (x,y) in tree:
                tree[x,y][1] += light/2
                light        /= 2


def grow((x,y)=(0,0),flow=0):
    type,store,children = tree[x,y]
    food = store + flow
    if type == 5:
        if food &gt; 1:
           tree[x,y][0] = 6
           tree[x,y][1] = food-1
        return
    elif type == 6:
        if food &gt; 3:
            tree[x,y]=[5,0,[]]
            if min(abs(x-xi) for xi in roots) &gt; 4:
                tree[x,0] = [2,food,[]]
                roots.append(x)
        else:
            tree[x,y][1]=food
        return

    if food &lt; 1:
        shuffle(children)
        for c in children:
            grow(c)
        return

    sites = []
    x0 = x+directions[type][0]-1
    y0 = y+directions[type][1]
    for i,t in enumerate(placement[type]):
        if t and (x0+i,y0) not in tree:
            sites.append((t,x0+i,y0))

    if sites:
        t,x1,y1 = choice(sites)
        t1 = choice(t)
        children.append((x1,y1))
        tree[x,y][1]=food-1
        tree[x1,y1]= [t1,0,[]]
        ymax[x1] = max(ymax.get(x1,0),y1)
    elif children:
        shuffle(children)
        for c in children:
            grow(c,food/len(children))
        tree[x,y][1]=0
    else:
        tree[x,y][0]=5

def output():
    X = range(min(ymax.keys())-1,max(ymax.keys())+2)
    for y in range(max(ymax.values()),-1,-1):
        s = ''
        for x in X:
            s += format[tree[x,y][0]] if (x,y) in tree else '_ '[y&gt;0]
        print s


roots = [0,20]
seasons = [10,40]
tree = {}
ymax = {}
for r in roots:
    tree[r,0] = [2,0,[]]
    ymax[r]=0

for season in range(max(seasons)):
    shine()
    shuffle(roots)
    for r in roots:
        grow((r,0))
    if season+1 in seasons:
        output()
        print


I'm curious to see a golfed solution.