Loads of humus, leaf mould, rotted manure, home made compost, compost from pots when you repot, anything fibrous and rottable. My Mum once buried an old wool matress on a really awful patch. You can add some coarse grit but some people don't recommend it, I forget why. If you chop autumn leaves with the lawnmower (next year!) you can put them on as a mulch. You can even lay lawn mowings on as a winter mulch.(Some people advise against it but it worked well for me) You might need to add a bit of nitrogen the folowing spring but it will improve the texture. It may take several years to make really nice soil but every little helps. Growing whatever will grow helps as well as the roots help to break it up. Roses do well on clay and we once improved a bad bed just by growing some dwarf michaelmas daisies in it for a few years (common ones not a fancy variety)
You could add some lime too if its acid.

dig in all your kitchen veg waste tea bags and shredded paper, etc, buy and dig in peat moss. you could also plant potatoes. its said you can compost anything that has lived, but don,t add cooked meat as it may encourage vermin.

Agree with everything except the peat, not because of the destruction of peat bogs, but because it does absolutely nothing to improve a clay soil.
Also get a cheap Acid testing kit and find out the pH of your soil. Then add lime at the appropriate level to bring it up to neutral, if needed. The lime causes the very fine clay particles to clump together and thus improve the soil structure(flocculation).

There used to be a product named Claybreaker which worked well for me. Owdboggy is there different types of lime? for different jobs. I used old lime mortar in the herbaceous borders and it worked wonders on the plants. I think that was the magic ingredient.

There are different types of lime, but generally the one used in gardens is Calcium carbonate. The lime in old mortar would be Calcium hydroxide which is the same stuff, but after being burned and having water added to it.
There is also Dolomitic limestone which is Calcium magnesium carbonate and has a slightly different effect on soil.

Hi, welcome to GoY, along with all the above, I would reccomend that you double dig the border, and improve the clay soil to a greater depth, which will also improve the drainage, Derek.

Thank you Owdboggy. I was going to add this to my favourites but that does not appear to be an option so I nominated this for Goypedia under soil types. It ia an often asked question not necessarily on goy.

Well I was summarising very much so, there is a lot more to it than I put in this post.

I'm sure there is Owdboggy but I don't think I need to know all the details of everything. If someone wants to know more I'm sure you can keep them right. The last mentioned one is the one which confuses me because I can never decide if this is akin to tufa or Cotswold sandstone.

Tufa is made when lime rich water (any kind of lime) trickles through moss or other vegetation and forms a conglomerate in which the original organic material decomposes leaving a porous 'rock' behind.
Cotswold stone is a type of Limestone called Oolitic limestone. This was laid down in a shallow tropical sea where the skeletons of the creatures providing the calcium carbonate formed into tiny pebbles which rolled about getting rounder and rounder and bigger and bigger.
And now you are testing my Geology to breaking point.

Thank you for that explanation. I know a lot of alpine plants grow well in tufa. My OH thought I could save a bomb on tufa rock by using Cotswold stone instead. It comes in nice slabs ideal for a miniature garden. I hope you do not mind but old age is catching up and I like reminders of interesting facts so I copied this in to Word for future reference. They do not call the 3rd age a second childhood for nothing. Simple explanations often suffice.

Hypertufa is easy to make and almost as good as the real thing.

Boy have we strayed from the original question. Sorry Lellieann.

Hi Lellieann and welcome to Goy. I hope you got enough info to get you started on your clay breaking garden. Have you got plans about what you want to do with it. I'm all for encouraging the grandkids as are many other members. We do tend to go round the houses a bit as a thread of a blog wanders down some unexpected routes. I hope you will enjoy that side of goy too.

AScots gran let me know if you want to make your own hypertufa - I've got a book with instructions. Never done it though.

I have a Blog on here on how to do it.

Thank you both but I will have to say no thank you to both of you. I wanted some rocks to build up some height in my 'fish box' alternative troughs. They are nice and light to move. I got more than enough tufa for what it would have cost me to buy cement. The local garden centre was selling all their landscape rocks and gravel at half price on Wednesday. I believe it is no longer PC to use tufa but now I have it i will not worry too much.