One of the best natural material you can think of is bamboo.
If you have some space left in your garden, bamboo can be renewable natural ressource.
Just be aware of the fact, that bamboo can spread widely and grow very fast.
Taking out the roots might require some stronger tools as the roots are very strong.
As it is very flexible and very strong at the same time, you can use it for different applications.
1) As garden sticks
2) As mulch
3) Or to produce beautiful and useful things
This curtain hanger in a sleep-out for instance I created after finding the perfect size of bamboo.