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Tropical Fruit Discussion / Re: Nitrogen Fixers
« on: August 18, 2019, 09:22:27 AM »
Here in North Florida, the best nitrogen fixing tree I've found for interplanting among fruit trees is Enterolobium contortisiliquum. Seedlings are already nodulating at six weeks old. Planted out in our sandy soil, they grow extremely rapidly, with a spreading form. If allowed to grow untrimmed, in ten years the trunk is often so big I can't reach my arms around it.
Their tissues are so full of nitrogen that sometimes when you break open a fallen stick from them, the inside of the stick reeks of ammonia.
In their first few years, these Enterolobium trees cast a light shade which can be helpful for getting some kinds of young fruit trees established (as these N-fixers get bigger they cast denser shade). They're easy to coppice or pollard - if at any point you decide they're getting too big or casting too much shade, just cut them back with a chainsaw. They'll throw out sprouts from the cut point, and you can then cut those sprouts back annually to maintain them fixing nitrogen without excessively shading your fruit trees.
They make lots of pods here, but I only rarely see seedlings pop up on their own. Scarifying seeds is helpful for germinating them, and the rarity of spontaneous seedlings maybe results from the absence of large animals here eating the pods & scarifying the seeds.
During colder winters here, they freeze back partially, then in spring they sprout out from wherever they froze back to. I've seen trees take 15F(-9C), which killed them back to major limbs, but not all the way to the ground. In areas with colder winters, presumably they would freeze to the ground every winter as a dieback perennial.
Their tissues are so full of nitrogen that sometimes when you break open a fallen stick from them, the inside of the stick reeks of ammonia.
In their first few years, these Enterolobium trees cast a light shade which can be helpful for getting some kinds of young fruit trees established (as these N-fixers get bigger they cast denser shade). They're easy to coppice or pollard - if at any point you decide they're getting too big or casting too much shade, just cut them back with a chainsaw. They'll throw out sprouts from the cut point, and you can then cut those sprouts back annually to maintain them fixing nitrogen without excessively shading your fruit trees.
They make lots of pods here, but I only rarely see seedlings pop up on their own. Scarifying seeds is helpful for germinating them, and the rarity of spontaneous seedlings maybe results from the absence of large animals here eating the pods & scarifying the seeds.
During colder winters here, they freeze back partially, then in spring they sprout out from wherever they froze back to. I've seen trees take 15F(-9C), which killed them back to major limbs, but not all the way to the ground. In areas with colder winters, presumably they would freeze to the ground every winter as a dieback perennial.