I need a category of say Tree's, with a product of say Oak Tree, with just a short description. Then on the same product page list/check boxes offering seed, small tree, large tree, bare rooted tree.
 
All items being part of stock control and individually priced with different shipping weights.
 
Any ideas how I can do that. As it does not come up on any of the demo products.

Very good question, can also apply to other things such as shoes, with extra goodies such as socks, laces & polish as extra options to add to the purchase.... Viart can you give any help here?
thanks!

Have you looked at product options - this will allow option (e.g. seedling) weight, stock level, hide if out of stock, variable prices, etc.
 
If you select to edit products you find, for each product -
 
The Product Name
Prices | Images | Options & Components | Specification | Related | Categories | Accessories | Releases
 
Click Options & Components beneath the product name.
 
Chris