Smart Plants!

Thorns on either side of a locust shoot.
Thorns on either side of a locust shoot.

I need a structure to provide shade to my hydrangea, and I've been thinking some kind of nanotech could do the trick. Currently known requirements :

1. Shade only goes out during the summer
2. At least thirty feet up, on a durable structure
3. Low maintenance
4. Fixes nitrogen in the soil
5. Self replicates
6. Inexpensive to build
7. Smells good in the spring and provides nectar for bees
8. Can do double duty as posts
9. Rot resistant
10. Massive carbon sink

I will draw your attention to the photo above, which illustrates requirement #10 from my requirements traceability matrix, which is that the structure needs to protect itself while it's being built.

You guessed it, I'm planting more locust trees!