Startup idea: GMO trees for rapid, green architecture, like bridges, fencing, simple structural supports. Some species of Bamboo can grow at a rate of up to 1.6in/hour so it may be practical to engineer a wood with the right material properties to grow into trained structural shapes in a span of months, as opposed to decades in the OP.
Hell, I'd love a living bridge in my backyard that I could have grown in a summer or two.
Sounds like a fantastic way to create more invasive species of plants that will displace native species.
They introduced gorse to New Zealand as it was good for creating hedges on farms. It's an horrifically invasive plant that's incredibly difficult to get rid of. It's fast growing, with hardy seeds that can lie dormant for 50 years. You clear it out and it just keeps growing back.
It covers 5% of the country, growing practically everywhere outside alpine conditions, and strangles out other species, especially in areas cleared of native forestry. Animals won't eat it because it's spiky, so it needs to be either burned, bulldozed, or cleared with herbicide.
He's really are beautiful and inspiring structures. The challenge for commercializing these methods is that they are very hard to get certified and brought up to building codes. When I lived on the big island of Hawaii I have a lot of friends who were building really cool stuff with bamboo but found that when they went to actually get the building permits there were only a few types of joinery which were allowed for actual legal residential or commercial buildings.
Hell, I'd love a living bridge in my backyard that I could have grown in a summer or two.