Growing plants through tarmac (by design)

[DavidC]

I have a cunning plan - and you guys will likely know if it makes sense or not....

Tarmac driveway, about 30 years old, good condition, edged one side with a brick wall about 300mm high with a timber fence on top. Want to grow a beech hedge against the fence, no more than 1m high.

Too much work to dig a trench and redo edge of tarmac.
Could grow hedge in pots (Beech is slow grow with not much root spread) but would need lots of pots and they would need water in summer.

So - How about drilling holes in the tarmac with a 150mm core drill that I hapopen to have here ? Have done a test bore and once I get about 200mm down there is a good quality soil (not clay and stone).

Hedge supplier can't see a problem. Fill the hole with soil and trees should have food and water they need (driveway drains toward wall but doesn't flood).

Seems to me like it might work, nothing would get close enough to break the edge and the 150mm hole looks neat.

So, is anyone screaming nooooo yet ?!
Any other problem I have overlooked ?

[seanandruby]

Weeds grow through tarmac so does grass. a tarmac scree very novel, suck it and see, you can always dig it up if they don't take.

[TarmacLady]

I'm not the horticultural expert, but my biggest worry would be the oils, etc., given off by the tarmac and leached into the soil. I know you can't use solvent-based asphaltic paints to waterproof ponds or flowerpots for exactly that reason.

Blimmin' weeds will grow anywhere, regardless, but I don't know how tolerant beech is to those chemicals. Might be a question to put to a nurseryman.

[lutonlagerlout]

davic said

I have a cunning plan

could this be baldrick mark 5? lol

as sean says suck it and see,

LLL

[Pablo]

NO NO NO NO do yourself a favour and hit yourself with your shovel. This will never work and if the plants do survive then they will be the mangiest things ever. Plants need not just water but minerals none of which will exist in a sub soil that has been covered for 30 years. Leachate from the tarmac will almost certainly be tainting the sub soil also. Beech is quite a fussy tree it needs light loamy free draining soil and plenty of water. Hornbeam which is a more common type of hedging and often confused with beech is much more tolerant of poor conditions. It may be more suitable but will probably die too. Also the holes would need to be at least 450mm wide to give the roots a chance of establishing as they are both a very shallow rooted tree.

[flowjoe]

When contractors build large car-park areas and they want to add tree features they excavate down to decent ground and install concrete/plastic rings and fill with decent soil, they then plant the trees/bushes etc within the said rings.

This gives the root systems access to decent ground and confines the roots from the tree/bush so that it doesn`t get access to drainage systems or lift the T-Mac etc............ however they must work out the size of the fully grown tree and the root system required.

It may be possible to sink 150/225m shafts for a hedgerow which to me sounds like a lot of work, but you should really speak to a specialist gardening forum before you do anything.

Hope this helps

[DavidC]

Cheers guys, looks like I need to have a rethink.
Might look at using something less sustantial like honeysuckle instead of beech - or laurel which seems to grow anywhere.
I could put the plants in wood troughs which would fix the soil quality problem but mean I would need to water, not what I want to do.
David C