yes you must ... nothing is going to grow up thru 12 inches of soil ...

first.. if you want 12 inches.. think about adding 15.. so that when it settles ...you actually have 12 .. much more important.. at the lower end.. if you want 6.. and put 6.. you might end up with 3 ...

next .... take out the plants on one side ... improve that area .. jam the plants back in ASAP ... close together ... simply to HOLD THEM OVER...

remove other half to the new area.. still jammin ... lol ... do second half ...

then anytime next summer.. start moving them around ...

with this method ... you can make it a 2 weekend project.. it just gives you alternatives to killing yourself on a none day project ... ... presuming this isnt checkbook gardening ... and you will have a 10 man crew out there ...

the VERY MOST IMPORTANT VARIABLE... will be tracking down.. and securing GOOD SOIL ... this is not simply going to be calling the closest place.. and ordering up a truck full ...

you want to find a good peat based soil ... with some amount of sand for drainage.. perhaps a new post.. if you wish to discuss soil science ...

so pay up front for good stuff.. and you will be rewarded ...

now ... the real question.. is 12 inches enough ... for high compact clay ... if you are hoping to garden COMPLETELY on top of the clay ... you might want to consider 18 to 24 inches ... i do NOT know ...

but the one thing i do know.. DO IT RIGHT THE FIRST TIME... there have been too many garden projects in my life.. that i finally won.. THE THIRD TIME I REDID IT.. lol

good luck ...

ken ...

Fill in the missing words in these well-known sayings ;-)

'If a job's worth doing, it's worth doing .......'

Alternatively:

'It's a pity to ...... the ship for a ha'p'orth of tar.' (Where 'tar' = effort)

You really need to bite the bullet and remove all the plants. If you dig them out with enough soil around the roots they should be OK. (The kale BTW will be over by next summer anyway). The herbs, especially, would hate having their crowns covered in 6 inches of stuff, although the sage might be OK if it is really a small bush ie about 3 feet tall and wide.

I'd remove the plants then fork up the base of the bed to improve the drainage and break up the clay a bit. Then add your new materials. Then replant the plants.

You will essentially be burying the plant crowns and subjecting them to rot. Also, if somehow they didn't rot, they may not have the energy to get through that much soil. Therefore, I think many would perish. I would transplant them in Spring. Balloon flowers can be moved, but you have to be sure you dig a very wide and deep hole and really get those roots.

Raising a bed is generally a good solution for poor drainage, but if the drainage is especially bad, it may not solve the problem as the water could back up at the clay line and saturate your raised bed as well. I would suggest trying to amend the exisiting soil with compost. However, to really amend the soil well, you have to temporarily remove the plants -- so you might as well raise the bed if you are going to all that trouble. I would really work the compost into the existing clay 6"-12" or so deep to try to improve the drainage before adding the soil for the raised bed.

Also, I wouldn't use peat moss as a soil amendment because it retains moisture (when you want the opposite), it steals nitrogen from the surrounding soil as it decomposes, and doesn't add nutrients to the soil. Top soil is also troublesome because its content is not regulated so you have no idea what you are getting. It is good for filling in large holes and raising a garden bed, but I would mix it with a pretty heavy dose of compost (no less than 1/3). See the below link for more information.

Here is a link that might be useful: Improving Your Soil

Thanks everyone.

My mom planted the balloon flowers so I'll need to see if she's okay with me trying to transplant them. Otherwise maybe I'll try a smaller raised bed towards the back where we have open space without any of the perennials that I don't want to risk killing.

Last year I worked the soil open parts of the soil 4-5 inches with a rototiller. Then added compost and top soil and worked that in. Maybe it just wasn't enough, but the soil compacted back down again. I tried some root crops this year but none of them seemed able to grow well in that soil.

I had some success with my raised bramble bed using 1/3 peat, 1/3 top soil, and 1/3 compost. But those like acidic peaty soil.

--The kale BTW will be over by next summer anyway--

It's already 5 years old and a 3' high monster. I had to hack it back a ton earlier this year because it was crowding out the tarragon. I think it's a type of Blue Scotch. Tasty, but grows like mad.

Interesting on the kale, I was curious and googled and saw most varieties are bi-annual. This one is definitely perennial. It was labeled blue scotch, but I have my doubts on that now. It has self-seeded other plants, but the original two were there for five years if not more (I dug up all but this last one to make room last year).