[DanielCoffey]

Having just moved into our new property in South Ayrshire, I have been looking around the borders of the site with a mind to spreading some grass/wildflower mix and need some soil prep advice.

I am well aware I am past the time for seeding perennials for this season so have the option of putting grass only down now and then raking and adding the perennials this autumn OR leaving the soil bare till autumn and trying to improve it with a very thick mulch.

It is very heavy clay soil and is badly compacted from machinery. In the recent rains there is free-standing surface water that takes half a day or so to drain. Overall the site does drain except in the digger track marks.

The edges of the site are under sparse but mature trees (Oak, Beech and Ash, mainly) of between 20 to 40 years age. There will be Hornbeam and Mixed Hedge plants put in at "five per metre" this winter around three edges to cut down on the wind.

There are lots of stones and builders hardcore mixed in with the clay (up to 50% in parts!) which I am assured the site manager will have harrowed shortly. Apparently he has budgeted for a "light and sandy topsoil dressing and we will seed and roll any grass if you provide it" but I have been thinking... given that the soil is so excessively clay should I pay a bit extra and hit it with a really thick mulch a-la "no dig method" and leave it untouched till the autumn?

The area I have to cover is large and the plot is about 25m by 30m although the bungalow takes up a good 10m by 16m chunk of the centre. There is a chipping driveway at one end.

So... harrow, topsoil and grass OR harrow and uber-mulch OR something else? What do you think?

[AlaninCarlisle]

It's not dissimilar to a situation I found when I decided to create a new veg patch alongside my polytunnel in the field at the back of us. My new bed was approximately 10M x 8M, on poor clayey soil just about 20cm deep below which is heavy clay and broken rock, something the locals call roach or roche..

My solution was to roughly turn-over the soil to let it dry out and then spread a thick layer, maybe 20cm thick again of horse-muck, leave it overwinter to settle and then till it until well-mixed. That was about eight years ago and every winter I keep on adding copious amounts of muck and garden compost. I now have a great, albeit slightly sticky area that grows just about anything. The only downside is that, as you may very well realise, horse-muck can contain large amounts of mainly buttercup and clover seed. The generators of our horse-muck are our three geriatric Shetland ponies which seem to thrive on stuff that passes through them as indestructible weed seed

[Yorkie]

I'm afraid I don't know enough to answer your particular question Daniel, but remember that grass and wildflower mixes prefer nutrient-poor soil.  I don't know whether adding a nitrogen-rich mulch would unbalance the nutrient requirements or not.

[DanielCoffey]

Hmm... that is a very good point. I had forgotten that if I dumped organics on it, all I would encourage would be the weeds. It looks like I need to make sure they really mix in the light topsoil in large quantities then.

It is looking like I seed the grass this summer and then rough-cut it, rake it and let let the perennial seeds in at the correct time in the Autumn.

It isn't for crop growing - this is just the area at the edges under the trees which is why I thought of perennials.

Cheers folks - I am clearer about what I have to do now.

[Yorkie]

I seem to remember Monty Don doing something similar a couple of years ago on Gardeners World.