Plants damaging brick garden beds

[Rafaela]

We have these big gardens beds in our complex. Many of them have Australian natives which are destroying the brick walls searching for I think nutrients and water. Even though I have read in this forum that they do not typically do any harm to surrounding structures. We have removed a few including a lily .What is the best way to fix this problem? Remove all the bottle brushes? And yuccas? What should we plant that does not destroy the garden beds?

 

 

 

 

[Akanksha]

Hello @Rafaela,

A warm welcome to the Bunnings Workshop community! We're thrilled to have you join us, and hope you find it a great resource for useful D.I.Y. advice and handy tips and tricks.

Sorry to hear about your damaged brick garden beds. Our resident D.I.Y. expert @EricL should be able to assist you when he's back on the site later today. In the meantime, let me also tag our garden experts @Adam_W and @Noelle to see if they have any suggestions. 

Akanksha

[Noelle]

Hi @Rafaela 

The biggest problem that I can see is that the brick retaining wall is built from a single layer of brick only and it has no 'weep' holes for drainage, so it will always be susceptible to cracking and potential collapse no matter what is planted behind it.  The taller shrubs and yuccas have probably contributed to the problem but are not likely to be the major cause of the damage.

Retaining walls are required to hold back quite a weight of soil and moisture, so a non-reinforced, single brick fence construction is quite inadequate.

In its existing state, and with no weep holes for drainage, ground covers and similar small plants would be all that I would be game to plant. Anything that has a root system of any consequence will almost certainly cause damage to the current wall.

In my opinion, you have two options:

1.  Take out all the existing plantings and replace them with small plants that do not have extensive root systems

2.  Remove the soil behind the wall and reinforce it with either another layer of bricks behind it, tied into the original, or concrete and add drainage holes along its length to allow excess moisture to drain away, thus reducing pressure on the wall.

[TheHandySqirrel]

Hi @Rafaela,

I agree with @Noelle that most retaining walls fail due to lack of drainage. In your case, before you remove any plants, it is worthwhile investigating thoroughly what came first - did the roots just find a crack that formed due to lack of drainage? Has the raised garden bed enough depth for roots to find water or is there maybe a concrete bottom? I'm very conservative with removing plants and would only do so after I'm satisfied the failure didn't occur due to other reasons. You could also drill weep holes into the wall to prevent any future drainage issues. About a metre apart should do.

[EricL]

Hello @Rafaela

It's great that you've received excellent advice from @Noelle and @TheHandySqirrel. You now have two options on how to handle the plants and brick garden bed. My only reminder is that if you choose to remove the plants, please make sure to plan ahead and find an alternative spot for them or perhaps transfer them into large pots. 

To repair the brick walls the soil has to be dug out and the wall itself reinforced or part of it relayed so that the breaks and cracks can be rectified. Another possible cause for the brick wall to lean out is that there was no foundation placed at the bottom. 

If you need further assistance, please let us know.

Eric

[Rafaela]

@EricL @TheHandySqirrel @Noelle Thanks for all your advice. Just to clarify that we were told these garden beds are attached to the house gutters to slow the progression of runoff rainwater. The garden beds have a layer of gravel, then a thick weed mat and finally the soil. The beds have a pipe at the very bottom that allows water to drain into our existing OSD.

 

 

Once the roots from the natives hit the weed mat they stop. But then start going into the bricks.

 

I have camelias and tricolor Jasmin and seems to do well. 

 

[EricL]

Hi @Rafaela

Thank you for posting that extra information about the garden beds. I'm afraid that the brick wall is no match for the roots of the native plants in your garden. I'm wondering as well if the water underneath has softened the foundation of the brick garden bed. It might be something that you'll need to look into if the opportunity presents itself.

If you have any other questions we can help with, please let us know.

Eric