Can trees grow in concrete?

12 June 2018

Question

Does concrete impact how trees grow in cities?

Answer

Do trees get enough water in city pavements? Chris put this to Eleanor Drinkwater, who got to the root of the problem...

Eleanor - That is a really good question. Trees, and plants in general, can be amazing in adapting how they grow to the different environments in which they are. So you can think about something like a willow tree, and if you plant it by a river it might not put down very strong roots because the water’s right there. It can be a problem with willow trees that they might flop over because they just don’t have the support structure there. Perhaps with the trees that you’re talking about, they have much more in depth root structures that’s adapted to the environment so they can spread out and find what they need.

Chris - Do you also think that it could be a factor that if you have concreted over the ground, actually what you’re doing by doing that is trapping water in the ground? Because the Sun’s not hitting the Earth’s surface and therefore evaporating water so the Earth might be losing a bit less water, so the tree might not actually have to try so hard to get at ground resources as it normally would. There’s less competition and there’s less evaporation.

Eleanor - Yeah, that’s a very good point.

Chris - In my experience, lots of trees that are grown in that way end up solving the problem for themselves by basically turning the pavement into a trip hazard, don’t they? You just get this massive load of dislodged paving stones and the tree says, I don’t care get these out the way. Because it’s testimony to the power of water really, isn’t it? Because these trees grow and then they’re using water for hydraulic pressure to split rocks and concrete out of the way so the tree can grow. Thank you Eleanor.


Comments

Yes of course concrete affects trees, because it impacts the soil and prevents air, water and nutrients reaching the roots, which are primarily within the top 12"/30cm of the surface. Those roots cannot exist, so they have to go deeper where there is no oxygen or nutrients. Rain cannot penetrate concrete. As these trees grow they will become weaker and sicker. Leaves become yellow, branches are twiggy, it becomes suseptible to disease. If the roots can crack the concrete they may survive.

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