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Pacific Northwest Gardening: How deep is my garden?

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Forum: Pacific Northwest GardeningReplies: 6, Views: 76
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Seattle, WA

June 12, 2012
9:46 PM

Post #9163041

Sorry, just trying to be catchy. I really want to know how deep I need to dig to renew a bed that was never properly done to begin with. I am removing massive quantities of rocks, some of them about six inches around. Mixed in with these is a layer of what we used to call hardpan, an impenetrable sand that is more like rock than sand. Now the bed itself is not that big---maybe 20 or 25 feet long by about four feet wide. I plan to make it my Japanese garden annex, with an assortment of shade loving plants and some that I just HOPE will be shade tolerant. So far my big nemesis has been the rain, along with what to do with all the rocks. I am digging with a fork, but am I stupid or something? I am basically digging a hole, but when I stand in the hole, I am then packing down the dirt that I hope will be lite and fluffy later on. At first I used a mattock to loosen up the topsoil that was choked with weeds. That worked well, but it's treacherous inside the hole, plus a bit too heavy for me after awhile. Had this spot been bigger, it would have been worth it to rent a machine. I am trying to be tidy, as I just repaired the fence and don't want to damage it. I know I am whining a lot, but I just want this to be over. A plant guy on TV said to just plant around the rocks, but honestly, when you have too many rocks, you cannot insert a tool to dig weeds in the beds or in the lawn. I just want to prepare this bed ONCE! Does anyone else have experience with this situation? Obviously the water must be going somewhere, or my yard would be a flood zone. I am currently digging down about a foot.
Salem, OR
(Zone 8b)

June 13, 2012
6:33 AM

Post #9163329

I think a foot should be good. Then add a lot of good soil and compost---so much so that the bed becomes mounded in relation to the rest of the yard. After a year, the new soil will pack down and it will no longer look mounded. Find a good reputable soil place, and have them bring the soil and/or compost by dump truck.
Union, WA
(Zone 8b)

June 13, 2012
11:01 AM

Post #9163644

At my old house I had a spot over the septic that I left bare and threw all my rocks in there. It is amazing now many times I needed a rock out of there. Now I just throw them in the back of the bed for later use. Sounds like you have a mighty project going on.
Rose Lodge, OR
(Zone 8b)

June 13, 2012
2:04 PM

Post #9163873

I might go a little deeper than Stephanie suggested but instead perhaps use the rocks to border it, making a raised bed? Would help with drainage to.


Everett, WA
(Zone 8a)

September 13, 2012
7:42 PM

Post #9274533

I almost always dig my beds down a little, and also raise them up a little. Every inch of raised wall is one inch down that you do NOT have to go.

I also like to remove the (awfull, sterile, sticky) clay from my beds. I pile it elsewhere and eventually screen and amend it - a lot. Meanwhile I back-fill the new bed with a batch of soil that I made earlier.

I would excavate enough to see how your hardpan floor slopes. If the floor slopes down to some point or trench that leads away to a lower spot, you'll have good drainage even if the hardpan is water-tight. I like the floor of every bed to be higher than some clear path down a slope. Uually I have to dig a mini-trench with the blade of a mattoc k, used like a hoe. If your clay is like mine, the walls of that slit trench will last as long as concrete would. If you wnat to be fancy, fill the slit with coarse garvel or pebbels. (Screened from the soil you excavatyed, maybe.)

I wouldn't worry about trampling the hardpan floor tighter. If you want, the very last step before backfilling the bed with good soil can be chopping a little more at the floor with mattock or pick - scratch it up a bit while it is moist.. Then lay some compost or amendments right on top of the scratched floor. Then backfill with good soil.

If you don't want to remove ALL the soil fiirst, maybe you could drag it to the left, finish the floor on the right, then move the soil from left to right and then finish the left-side-floor.
Seattle, WA

October 11, 2014
1:44 PM

Post #9956936

Thanks so much to everyone who answered so thoughtfully. So far, all the plants are surviving well. I put in a couple of small maples, a few hostas and a variety of ferns and heuchera. There's a rhodie (no blooms on that one yet), a female Japanese lantern, a small weeping larch, and a couple of plant sale evergreens from Kubota Gardens. I was told they wouldn't get broad--the leaves are similar to boxwood leaves. The people at those sales are pretty excited about their "babies", and love to send them to the right home. I love to support the Gardens, too!
Lake Stevens, WA
(Zone 8a)

October 12, 2014
9:50 AM

Post #9957298

velveteena-so how much digging/rock removal/amending did you end up doing there? Whatever it was, it sounds like it was enough, as the plants grow well. I have never done a major digging job into my hardpan, for the reasons you mentioned. Even a little hole is a lot of work with the mattock!

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