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Fruit canes in Heavy Clay Soil & low light
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Posts: 6
in Fruit & veg
Hello, I'm fairly new to this gardening business and am looking at putting some raspberry and blackcurrant canes into my garden. The area where I have space is on the south side of my west-north-west facing garden. This clearing receives direct sun during the first few hours of the morning (it is shielded by a 6 foot fence and would have sun for the entire day otherwise), would this be enough to yield a decent enough crop? As the title suggests this area is also heavy Clay and will require being replaced. How deep would you dig down and what would you replace the soil with? On this topic I've also just bought a dwarf apple tree on M106 root stock (if I recall), how deep would you dig to ensure the roots don't become waterlogged because of the clay? Your advice is appreciated before I invest time only to see failed plants or crop! Would love to be able to make use of every inch of space in my garden 
Many Thanks!
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Regarding the soil, Black Currants are very tolerant of heavy clay, as long as it isn't water logged for long periods they will flourish in it [this is from personal experience]. That said, incorporating compost will improve performance. For the Raspberries, they grow in woodland soil in the wild, so incorporate plenty of compost or leaf mould into your clay and raise the level slightly above the surrounding ground as they don't like water logging at all.
Regarding the light levels I think your raspberries should be Ok being woodland plants as I said before. I successfully grow Red currants in an area with similar light levels to your proposed area, so it would probably be OK for Black Currants
The way to improve clay soil is often discussed here; digging out and replacing is hard work and very expensive. I guess that you would need to remove about 2 - 2'6 and buy in top soil. You can improve the clay instead for long lasting, high quality results. Clear the bed and dig in as much muck as you can get and coarse grit,too. Well rotted manure, any animal, garden compost, seaweed. Some councils sell large sacks of composted garden waste and some horse owners give away stable muck. You cannot really have too much. Dig and break up and mix, leave it open to frosts and dig and mix some more.
I can't comment on fruit growing because I don't grow any but I know raspberries dislike clay
I should look it up, but off the top of my head I also think the ph (acidity) of clay is wrong for raspberries (raspberries like slightly acid soil, clay is slightly alkaline - or did I get it the wrong way round?)
I have raspberries growing in half of a whisky barrel against a 6' fence, on the east side of it so probably quite similar to your area, they seem to do pretty well. The top flowers are above the fence now (autumn bliss so not quite ready yet, will need to protect from the birds soon though). Using containers means you can use the right kind of compost if your garden soil is unsuitable.
Here's a photo just to give you an idea how waterlogged it gets! This is an old photo though, there's now a raised border to the right and top. The raspberries would go in the left between the gravel and paving slabs.
If it gets very wet and you dig out the clay, water will drain into the lighter soil and settle there. You would do well to raise your new bed so that the plants are clear of most of the waterlogging.
Clay soil is potentially very fertile as the nutrient-laden water sticks to the tiny particles, so don't get rid of it, but do improve the drainage it with lots of organic matter, as Posy says. Get friendly with your nearest riding stables as they'll have literally tons of muck to get rid of. If it's well-rotted you can dig it in straight away but if it's fresh you need to stack it for a year (during which time it'll give off heat and yiu can use it to make a hotbed). Leaf mould is great for raspberries too.
Both raspberries and blackcurrants need a lot of nutrients as you remove a lot of the growth every year and they have to make more, so they'll also want fertilising - bonfire ash (kept dry since the fire) in spring is ideal as it supplies a fair amount of potassium.