Mound off contour

I have to completely repair 100m of overgrown hedge line - hazel, hawthorn, gorse, blackthorn - all the thorny things... at the moment, most is covered in brambles, and ivy, which are also thick and thorny

I'm in the UK (as if the hedge species didn't give it away), and we get a fair whack of rainfall accordingly. This land is on a slope near the bottom of a valley, stony and VERY clay land.

My plan is:

To scrub out as much bramble and ivy as I can (in the rain, by hand...hard, tedious), and cover the ground in black plastic for a year.
Tidy the fence itself, re-tighten, increase the protection from rabbits
Coppice most of what's in there, to try and encourage growth
plant a line of black locust and seabuckthorn, 2m inside the fence line (the other side of the black tarp, which is the south side). These will need to be mounded up a little because it is so wet down here. This location is generally, on a ridge along the slope.

My concern is planting a line of trees on a (albeit small) mound, on a slope that is OFF contour stands to get me in trouble. The contours run about 45° across the fence line, so the fence crosses the shape of the land.

If I plant them straight into the ground they might be OK, but it could well be too wet for them - the sea buckthorn certainly.

What do folks do when planting along a boundary line? These invariably do not follow contour lines. Do you just plant the row and hope for the best?

Any tips on stopping brambles and ivy from returning appreciated too...

Seabuckthorn should be fine its a coastal plant at the end of the day.

Black Locusts do best in well drained soil and reading about this Robinia dieback most seem to be suffering after excess wet conditions.  

https://www.rhs.org.uk/advice/profile?pid=401

I have seen plenty in heavy clay that were quite happy, the question is how boggy your wet soil is going to be.

Some dogwoods (Cornus spp) survive well in flooded conditions and willow of course but they are not spiny. The only thing that springs to mind at the moment is hawthorn https://pfaf.org/user/plant.aspx?latinname=Crataegus+laevigata

Hi MJ,
Are you worried about water build up in rain and erosion, or simply the water logging of the roots of the (nitrogen fixing) trees you have selected?  Were they selected as spiny to be a barrier, supplementing the soon to be repaired hedge?  Does it have to be oriented along the existing boundary?
FYI I've got some sea buckthorn here, albeit only it's first winter. I was worried it may be too wet here on Skye so have planted it on steeper slopes and edges where it should be well drained at least.  I think Robinia will find it too cool here in summer....
Alternative nitrogen fixing tree for wet conditions is alder (Alnus cordata).  Not edible but I'm mainly growing for wood fuel and shelter.  It is very quick growing and loves damp.

Henry Jabel wrote:Seabuckthorn should be fine its a coastal plant at the end of the day.

Black Locusts do best in well drained soil and reading about this Robinia dieback most seem to be suffering after excess wet conditions.  

https://www.rhs.org.uk/advice/profile?pid=401

I have seen plenty in heavy clay that were quite happy, the question is how boggy your wet soil is going to be.

Some dogwoods (Cornus spp) survive well in flooded conditions and willow of course but they are not spiny. The only thing that springs to mind at the moment is hawthorn https://pfaf.org/user/plant.aspx?latinname=Crataegus+laevigata

Thanks Henry.

Its not wet to the extent that there is any standing water or anything like this. Its actually surprisingly diverse on this part of the property. Hawthorns and willows are abundant here.

Nancy Reading wrote:Hi MJ,
Are you worried about water build up in rain and erosion, or simply the water logging of the roots of the (nitrogen fixing) trees you have selected?  Were they selected as spiny to be a barrier, supplementing the soon to be repaired hedge?  Does it have to be oriented along the existing boundary?
FYI I've got some sea buckthorn here, albeit only it's first winter. I was worried it may be too wet here on Skye so have planted it on steeper slopes and edges where it should be well drained at least.  I think Robinia will find it too cool here in summer....
Alternative nitrogen fixing tree for wet conditions is alder (Alnus cordata).  Not edible but I'm mainly growing for wood fuel and shelter.  It is very quick growing and loves damp.

Thanks Nancy.

Its erosion more that concerns me. These trees were selected, primarily, for privacy over and above their spines. Unfortunately yes, they do need to be oriented along the boundary - at least this row does. Once these are planted I intend to plant all other trees on this slope (I intend an orchard here - south facing and surprisingly more sheltered than the flatter land below) on contour.

We have a lot of alder down low, and willow.

Mj,
Given that the existing hedgerow has been there for a while without (presumably) aggravating a tendency to erosion my feeling is that you'll be fine once you have some tree and shrub cover.
Personally I'd go for more of a mixture, but I like to spread my risks a bit, especially with climate uncertainty.  A search on the ferns website (I don't know whether my link will work but here it is The ferns search) suggested elder and field maple as well as a vast range of willows.
At East Devon Forest Garden Sagara has planted Italian alder round his field (albeit not sloped) and these will probably be a bit tall for you, since you don't want to shade your orchard too much.

Nancy Reading wrote:Mj,
Given that the existing hedgerow has been there for a while without (presumably) aggravating a tendency to erosion my feeling is that you'll be fine once you have some tree and shrub cover.
Personally I'd go for more of a mixture, but I like to spread my risks a bit, especially with climate uncertainty.  A search on the ferns website (I don't know whether my link will work but here it is The ferns search) suggested elder and field maple as well as a vast range of willows.
At East Devon Forest Garden Sagara has planted Italian alder round his field (albeit not sloped) and these will probably be a bit tall for you, since you don't want to shade your orchard too much.

All good suggestions and you make a good point about the existing hedgerow. Thanks.

There will be some birch up there too, maybe some alder, and willow. The willow I will plant from cuttings, its so abundant down the slope.

Shade shouldn't be too much of an issue - one piece of good fortune here is that this is the northern most boundary, so height helps me create a bowl effect.