If you can't dig easily, then heavy equipment enters the picture :-)) Something like a front or mini-loader, available at most rental stores. There is really nothing else that will address the problem of trenching in heavy clay any faster - certainly not any kind of soil conditioner. Those all take time to work.

Yeah, I was afraid of that... this cheap DIY project is becoming a beast.... still, the landscapers wanted $2500 to do it, I still don't think this is worth that!!

Actually $2500 is a pretty decent price for that. A French drain one of my clients had installed was less than half that length and not in rock-hard clay soil and theirs cost $3000. Landscape labor is not inexpensive.

Gypsum and compost will help over a couple of years - so it is not the silver bullet you are looking for. Gypsum is helpful as a soil amendment for adding calcium without also adding magnesium which locks the clay particles together.

If you are renting equipment, pay attention to the weight and consider how you are going to transport it. This isn't like picking up a rototiller at Home Depot - you are going to need a truck and several friends to move it.

About 18" deep and a foot wide... my husband ended up getting a pick axe basically ha! But it's working, faster than a shovel anyway!

Yep... pick axe. I just did 60' x 2 1/2' or so with a pick axe in my clay. I just loosened it to plant sunflowers though, digging it out is much tougher, but that's the way to go if you're doing it by hand. There is no faster way.

Ditch Witches, as mentioned above, will do the job just fine and are much easier. Rent it on a Saturday and most places give you Sunday for free. Renting isn't as cheap as doing it by hand, but it sure is easier!

I use a meadow creature broad fork to break clay that my tractor and plow struggle with.

Careful about the saturday/Sunday rental and read the fine print. I didn't and put 30 hours on a stumpgrider over a weekend. The 1-day rate was for 8 hours of use only-even if I had it all weekend. That's apparently an industry norm.

"What would a landscaper in a time crunch do to get the trench dug?"

Hire a couple of short muscular guys who know how to swing a pick.

You need a mattock or pick to bust up the hard stuff and then a trenching spade shovels to remove the chunks.

There's a reason it is called "pick and shovel work".

There is no fast way to make clay soils easy to work and gypsum is not one anyway.

What you need to do what you want is a power shovel, or a landscape contractor with one.

I'd be talking with the local power tool rental place and see what they have as others have said. You'd be surprised at some of the easy to use equipment there is. For this probably a walk-behind trencher would be ideal. Of course you'd have to get it there. If you or your neighbors need anything else done, a weekend rental is great and you can split the cost.

A shovel is totally the wrong tool, which is why it isn't working well. A pickaxe or digging fork work much better.

Pick mattock. A pick axe is normally used by firemen, it is literally an axe with a pointy thing (pick) on the other side. A pick mattock has the blade the other way so you can chop at the ground, and the same pick on the other side for prying out rocks. Probably swimming upstream here as most everyone sees a pick mattock and calls it a pick axe, but I'm just....wait for it....picky?

Tox-oh stop being such a wise adze. (Get it?) Seriously, broad fork. Swinging a mattock/adze is exhausting me just thinking about it. A broad fork uses my body weight and leverage instead of just swinging the thing. I dug a hole 7x25 by 4 feet deep in compacted clay.. Half of it was with the broadfork. Hardest part was lifting the clay chunks out.

Save yourself a lot of labor and rent a piece of equipment!! Digging by hand is not worth the time, effort and exhaustion in heavy soils. Specially if you need it done PDQ.

You asked what a landscaper would do and that's exactly it (I am a landscaper!!)

'Rock hard' makes me wonder if they have hit some caliche. Nothing to be done but get some mechanical equipment in there.

Not sure where (part of property) you are doing this but "Call before you dig = 811" comes to mind.

I know some years back my neighbor was putting in a fence and hit a telephone bundle. Lucky me was off the internet for a week. I'm pretty sure they whacked him for the repair.

Heavy guage hammer drills have an atted bit referred to as a clay spade. its a small shovel basically. Google bosch clay spade. They are the cheapest rental tool for digging.