Nitrogen Fixers

Driving back home from Chico yesterday, I asked Stephen to stop just past the bridge we cross to get home. Out in the field I spied what I had decided was a Black Locust. It was once a massive tree. But like most pioneers, these are not long lived trees. Still, this tree was at least 70 years old. But it was on it's way out. I could spy however dangling from its branches seed pods. Ahhh! I am always on the look out for those little seed packets. We looked at the cattle gate close by and since it was only latched, I scurried through and made haste to the tree. I must say I felt uneasy trespassing, sure someone would come out and yell at me across the grass. I stuffed my pockets with pods and made it back to the car. It was much cooler under that tree. But not one little tree seedling did I see. This is probably due to the cattle that frequent these fields.

These are mimosa seedlings. :)

Black Locusts (Robinia pseudoacacia) are considered by many to be weed trees or trash trees. I don't think I need to tell you what I think of these terms. These are trees with extremely hard wood which were historically used for fence posts due to their resistance to rot. The bees love them. They are also nitrogen fixing trees so would work well on the swale mixed in with our fruit trees and cut periodically. In the South and Southeastern parts of the USA, they can be extremely difficult to control due to their ability to reproduce quickly in a wet and warm climate. Many plants are not as well-mannered when placed in these environments. But here in our climate, they don't seem to travel much at all. This one Black Locust tree is surrounded by thousands of acres of grassland. And yet none of its progeny have survived.

By cutting nitrogen fixing trees and shrubs from time to time, they shed roots and release nitrogen into the soil. According to Geoff Lawton, you want to do this when the evaporation rate is less than the precipitation rate. So for us that would be end of Autumn when the rains begin. For a long time I was not sure if I had collected Honey Locust( Gleditsia triacanthos) or Black Locust seeds. But now that I have seen both up close there is no mistaking them. Black Locust's have much smaller seed pods and their leaves are larger and more green than the yellow- green leaves of Honey Locust. Honey Locust do not fix nitrogen but do accumulate minerals in their leaf litter. Also the pods of the Honey Locust smell sweet and taste sweet too. Seems obvious now but many of the pictures of these two trees are mixed up on the internet. Remember people, just because you read something on the internet doesn't make it right. Research stuff yourself! That includes everything I say. I collected my stash of Honey Locust seeds from the Raley's parking lot in Chico. They are all over the ground this time of year. If you do collect seeds this way you have to be careful about bug infestation and cars!

Another nitrogen fixing tree according to some sources is Albizzia julibrissin or Mimosa. I collected these seeds from trees in Corning. Super easy germinators, and again accused of being invasive weed trees in the South, mimosas are tough, beautiful trees. They give dappled light which is perfect for growing plants under, even those that like a lot of light. We get too much solar radiation out here, dappled shade is the way to go. I have also successfully germinated some Siberian Peashrub (Caragana sp.) both from Russia and Korea but it's slow going. And only one of my Tagasaste trees germinated and it doesn't seem strong still. All of these are also nitrogen fixers, the backbone of establishing a perennial food forest and improving soil health.