Forum: Site Works
Topic: Raised flower border
started by: Dave Meredith

Posted by Dave Meredith on 12 Sep. 2019,16:47
My neighbour has quite a large tree close to the fence. It overhanges into my garden and unfortunately very little grows under its shade. I've trimmed a few branches back so its not too shaded but the tree takes most of the water and nutrients to the point where the lawn hardly grows at all.
I would like to build a raised flower border under this overhanging tree. I don't want a straight border so I'm thinking of using upright railway sleepers and backfilling with soil. I was thinking of putting some kind of moisture barrier in before backfilling with soil because I dont want the tree roots growing up into my raised bed and I want the rainfall to be retained in the bed -not absorbed by the tree roots.
Is this a workable solution? Are there any issues I should be aware of and do you all think this should work?
Many thanks
Dave

Posted by Tony McC on 12 Sep. 2019,18:35
You need to strike a balance between creating a pond or reservoir for moisture, and building a feeding station for the damned tree, so the aim would be to fashion a pit with good-ish moisture retention, plenty of nutrition, but adequate drainage.

The basic idea to use upright sleepers is fine, but how much upstand? A good 'rule-of-thumb' would be to have at least one-third (minimum 2200mm) in the ground fully supported, prefeably with concrete, in the manner of a fence post. The 'inside' can then be lined before backfilling with a good, healthy growing medium.

If you have a well-drained plot, the lining can be root- and watertight(ish) with perforated pipes laid at the base and leading out to a soakaway or similar elsewhere in the garden, but for most applications, simply lining with a good quality root barrier membrane or composite, to inhibit encroachment from the tree roots, would be adequate and by far the simpler construction.

You may have to provide irrigation or regular watering if the tree is going to parch the plot, but that applies to most tree-lined gardens anyway, so no great additional burden.

It'll be interesting to hear how you get on.....

Posted by Dave Meredith on 13 Sep. 2019,08:11
Many thanks for your response Tony. It really
helps to have a second opinion especially from
someone with expoerience.
This border will not be huge - probabaly a half-circle with
a radius of 1.5 metres. I'm thinking of a height of about
half a metre or less.
I'm inclined to go with your membrane suggestion. My garden isn't that big and putting a soak-away in is going to cause more disruption than it's worth.
Once again - thank you!

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