A look at some nitrogen-fixers for food forests in Florida

I confess: one of the areas I overlooked at the onset of my food forest were the nitrogen-fixing support plants.

I've definitely been paying for it.

The middle of the food forest is pretty lousy soil, as is the Eastern half. I should have planted a ton of support plants before adding my fruit trees - or at least concurrently with them - but I didn't. I got caught up in adding the fun stuff and have been playing catch up ever since.

Over the last couple of years I've been starting nitrogen-fixers from seed and adding them to the food forest. I've also purchased a few, like the Enterolobium below:

That puppy came from fellow plant geek Oliver Moore. He's got some pretty cool plants in his collection and when he offered to sell me some potted Enterolobiums at $3 each, how could I refuse picking up a half-dozen?

Want to see what a big one looks like? Click here. They're amazing.

Obviously I can't let them get that big in my food forest. They, like the other nitrogen fixers, are mostly chop-and-drop plants that will add both mulch above the soil and nitrogen below as I aggressively cut them back every year.

Or as they freeze back, as is the case with this Royal Poinciana tree:

 

I've had the top of it freeze a few times but it's been coming back from below.

The royal poinciana is a wonderful and beautiful tree but it's a true tropical that can't take the cold up here. I'm wondering if it will keep living or kick off eventually. I would really dig it if it grew enough to bloom one year.

Now here's a tree that's considered a pest:

 

That's a "mimosa tree", one of our common invasives which also happens to be a good nitrogen-fixing tree. Keep them cut back and they won't set seeds. This one is planted next to a Chinese chestnut tree it's feeding every time I whack its top off.

The plant below is some sort of cassia or senna:

 

I'm not sure because I got the seeds somewhere and lost the Latin name. Whatever it is, it's in the pea and bean family for sure - and looks rather similar to this guy, a relative in the cassia clan:

 

That's a "Christmas cassia," a late-blooming ornamental shrub or small tree which is commonly sold at landscape nurseries. It's fast-growing and a good nitrogen-fixer, particular for small yards and edible landscaping projects where everything is supposed to look good.

The tree below is a bit on the weird side, but it's also lovely.

 

That is a Jerusalem thorn in full bloom. The pods or seeds are apparently edible but I've never gotten any.

The problem with using this tree as a nitrogen fixer is its incredible thorns and super-hard wood. Cut these branches and drop them on the ground and you're going to hurt someone at some point.

It's pretty, though, and works really well in arid conditions where other nitrogen-fixers may not grow. It's also quite attractive.

Another lovely tree is the "Pride of Barbados" tree, also known as dwarf poinciana:

They die back to the ground almost every year when the frosts hit, then return and grow to a few foot tall before setting lovely red flowers that look a lot like miniature royal poinciana flowers. Unfortunately, the tree is somewhat thorny so it's a questionable chop-n-drop.

Here's another thorny one that despite its sharp reputation also has multiple benefits to recommend its use:

That's a little black locust tree. They fix nitrogen, feed the bees like crazy, plus yield wood that will last for decades in the ground without rotting. It's a perfect fence pole tree for the homestead. I only have one at the moment but hope to start plenty more in the future.

Though most nitrogen-fixing trees don't yield anything you can eat, they do add a lot of life to the soil and make things quite a bit easier for your fruit trees. I've got a good list of possibilities in my book Create Your Own Florida Food Forest, which, incidentally, is now on sale for $2.99 as part of the Kindle Select program on Amazon.

Don't do like I did. Start with the nitrogen-fixers and mulch plants like Tithonia diversifolia, then plant your fruit trees.

They'll be glad you did.

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