If you’ve treated yourself to a new garden tree, then it goes without saying that you’ll want that tree to thrive once you’ve planted it. One step that many people take before planting a tree is to amend their soil, but is this always beneficial? Let’s find out…
Does Amended Soil Boost Tree Growth?
Many gardening guides recommend adding between 25-50% organic matter to the soil in a new tree’s growing area. This could be anything from compost to well-rotted animal manure. As a result, this increases the nutrient and moisture content of the soil, which will give that new tree a good growth boost to begin with.
However, it won’t be long before that tree’s roots reach the edges of your amended soil and start to make their way into native soil. This is when the problems start to arise…
Amended Soil vs Native Soil
Compared to the beautifully light, fluffy, and nutrient-rich soil that you’ve given your new tree, your native soil will be lacking. It won’t have as many available nutrients and it’ll be much denser and harder than the amended soil. As a result, once your tree’s roots start to make contact with this poorer soil, they’ll circle back around, preferring the more hospitable amended soil instead.
This means that the tree will struggle to fully establish. Instead of stretching those roots out far and wide, they’ll be restricted, similar to a tree that’s pot-bound. The effects of this may not be visible straight away, but it won’t be long before you noticed a dramatically reduced growth rate.
Soil Water Movement
In addition to affecting root growth, amending your soil will also impact the way in which water is able to move through your ground. This is because your amended soil will greatly differ from your native soil in terms of texture and moisture-retention capabilities.
During dry spells, water will quickly wick away from porous amended soil, filtering into your native soil to leave your tree thirsty. This may not be a huge issue for drought-tolerant trees, such as the Dragon Tree or the Grass Tree, but even drought-tolerant species do need a certain amount of moisture.
You may think that a heavy rainfall would rectify this, but it actually has the opposite effect. Yes, water will quickly drain through your amended soil, but with native soil being slower to drain, all of this water surrounding your tree won’t actually be able to go anywhere. As a result, the water will simply accumulate in that area, flooding out those roots. That drought-tolerant tree that was doing so well during your dry summer will start to suffocate and will eventually die.
So, What’s the Solution?
The best way to prevent the above issues is to stick with your native soil when planting a new garden tree. Yes, some trees do need specific soil mixes, but a mulch layered over the top of your soil can help to provide those nutrients. If the tree that you’ve chosen requires radical soil amendments, then you would be better off going for a species that will thrive in the soil that you already have. Picking the right trees for your garden will do away with the need for soil amendments, allowing that tree to thrive in the natural environment that already exists.