What to add to our heavy clay soil in readiness for planting

You need to add organic matter to break it up, compost, manure, bark chips a small amount of grit or sand(not builders sand) any of them dug in should help with drainage and lighten the soil up. Good luck it’s hard work.

Years ago when we lived somewhere with clay soil FiL used to save all his fire ash for us to dig in.

I think that the ash would have to be wood ash, ash from fossil fuels is a bit toxic.

As suggested above, and also any old horse manure with straw, mushroom compost etc. I have put tonnes of stuff on mine over the years, it is still pretty awful. Even spread old newspapers over the earth, soak them well, and then add compost/manure on top. It all gradually breaks down and encourages friendly worms.

Best advice is to see what thrives in your neighbours gardens, and go with that. For us, roses do well, and viburnums, all types.

I am not sure if you have room, but you could grow a green manure crop this spring, which grows over the summer, and is then dug in to improve the soil. www.greenmanure.co.uk/pages/choosing-the-right-green-manure

Double digging, with lots of horticultural grit, helps but is very hard work. It was awful here when we moved in (used to be grazing and nearly all clay) so we grew potatoes the first year just to break the ground up.

That's good advice from seacliff about neighbours gardens. Look out especially to see what thrives in neglected gardens.
30 years of adding home made compost has transformed the ground. I pour a compost/grit mix into any cracks that form in the summer.

I agree with Seacliff's advice too.
Where we lived in France the earth was pure clay but very fertile for certain things, mainly cereals. Even so farmers spread manure from their pigs and cows. Full of nutrients. We used to spread and dig in the soiled straw from the chicken house.
Also hard to work - sloppy and slippery when wet, concrete hard when dry.
Luckily previous owners had added organic material to one patch, where we grew our vegetables. The only things that didn't thrive were root crops, Except for beetroot and potatoes, which did well.
Roses , yes, but forget about your herbaceous borders, except lavenders, rosemary, and others from the mint family.
My favourite was an aromatic bushy plant with small yellow flowerheads - can't remember the name, begins with 's'.
Good Luck!

Add organic material, compost, some horse or farmyard manure. I bought some recycled compost from Lidl it was very cheap, very coarse not really good for potting but would help with clay soil, dig it into the top 4 inches and let the worms do the work.

ps the plant I was referringed to is Santolina:
www.crocus.co.uk/plants/_/santolina-chamaecyparissus/classid.4357/

I think I would be tempted to install raised beds over the present soil areas, fill these with good quality topsoil and plant accordingly. Clay soil is always very high maintenance despite adding grit, compost etc.

Yes raised beds are a really good idea. Wish I'd done that 20+ years ago.

We found that even with lots of soil improvement, some plants did well for the first few years then growth just stagnated and they did not thrive. Bulbs usually rot after a couple of years too. So now I have them in pots.

The roots were not able to penetrate the awful gungy clay subsoil. I think our soil is particularly bad though.

seacliff sorry to go on about our french garden , but about the depth of that claggy soil.
I once kept digging to open the soil for planting etc and found a blockage - it was a baby's carrycot, complete with mattress, covers etc. I was scared there would be something more gruesome inside but TG there wasn't.
In the war years many delicate babies died.

Oh my goodness Fennel, I would have been scared to look! I remember now I had some santolina years ago, it must have been killed by the weeds.

Our garden is on a clay hill, with a very high water table. DH dug out a very large deep pond years ago (with a digger). He did not have to line the pond at all. It was blue slip clay, we just waited for the rain to fill it up, and so that is one benefit of our soil. No pond liner needed.

I think I'd mix sand with it to absorb the damp cloggy clay.

Arrrh thanks everyone. Hopefully the garden centre will be open soon.

We have clay soil and it is challenging. We had new borders added at the edges of the lawn 2 years ago and I’m still trying to fill them with perennials.
It’s trial and error what will grow well as clay is either heavy and wet, or cracks appear when its a long warm spell.
Our gardener friend said keep dressing it with small grit and sand (gardener variety, not the red, building variety).
It is looking very pretty now with a mix of Salvia, lavendar, potentilla, geum, fuchsia, potentilla, echinacea, hebe, choysia. (Not all in bloom in May obviously).
Good Luck!

We had an allotment that was almost all clay one side. Agree with those who say plenty of organic material - soil conditioner, manure, anything to open up the structure. Ours grew good potatoes but not much else.