Allelopathic Trees

Sometimes I have a post that crosses subjects.  Right now I’m going to discuss trees (under plants/shrubs/trees) that can affect the development of your land (under land).

Trees can do so much for land.  They can cool the land, raise or lower the water table, block the wind so the topsoil does dry or blow away and they bring nutrients up from deep in the soil.

Some trees poison the soil as well.  Allelopathic trees chemically affect the soil to their benefit.  Sometimes this means that they enrich the soil.  At other times, they kill off the competition so that there is more water for their roots or their progeny have a competition-free environment.

I’m going to focus on the poisonous side of allelopathy.  It’s important to use this aspect of trees to your benefit.

The first time I heard the term “allelopathy”, it was related to a presentation by Sepp Holzer (btw, I recommend his book).  Sepp talks about “pine deserts”, places where only a few species of plants and trees can flourish.  I recommend researching this subject more.  I’m not going to delve any further, other to discuss which trees I am going to avoid.

It’s important to note that I don’t think all negatively allelopathic trees should be cut down.  My soil is poor enough that I don’t want to add anything that isn’t going to help me out, so I’ll be avoiding those types of trees for now.

There are three vectors that a tree uses to chemically change the soil.  They are from the root, from the stem and from the leaf.  Trees can change the pH of the soil, inject or take away chemicals, or inhibit/encourage bacteria in the soil.

I have to avoid planting trees that will hurt my land plan.

I also have to remove trees that will hurt my land plan.  

I’m concerned about the ponderosa pines on my land.  Pine trees are known for making the soil more acidic.  Some plants on my land indicated that the soil isn’t greatly acidic, but I still have concerns.  I’ll talk about soil tests in a different post.

I did a little research and found that ponderosa pine needles seem to inhibit the bacteria that develops nitrogen in the soil.  This is a big deal–I’m doing my best to develop plants that are nitrogen fixers right now.  These plants help bacteria that put nitrogen into the ground.

I think I’ll limit the “juvenile” ponderosas to the borders of my land.  There are a few towering ponderosas that I’ll leave alone.  They’re stunningly beautiful trees.