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Garden drainage

Posted by raydenl none (My Page) on
Mon, Jan 9, 12 at 2:11


The below photo shows a new garden both sides of a fence, sloping downhill left to right. Unfortunately it fills up with water on the right side when it rains because of the concrete mowing strips.

The garden will eventually be filled with bark, but I need to stop it from flooding first.

This is a new garden/house so the soil is quite compacted. I'm wondering if double digging the soil will be enough to add sufficient drainage to the soil. The water drains away quite fast at present.

Any other ideas?

Follow-Up Postings:

RE: Garden drainage

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RE: Garden drainage

I would say you have a definite problem.
Double digging will generally only make a deeper bucket unless you get through the soil that is stopping the water from perking.
(1) Remove the soil to 6" below the bottom of the concrete curb. Place 6" of septic gravel into the bottom. Put filter cloth over the top. Replace soil making sure the soil has good drainage characteristics. Install pipe under the curb leading to more drainage pipe that will take the water away. I have had to use electric sumps with a float valve several times
(2) At this point you need to visualize the planter as a flower pot. A big flower pot but a flower pot non the less.
Just like a flower pot it needs holes in it to drain. So one thing you might do is drill holes through the sides. You can rent the drill and bit. Put filter cloth over the holes. It will be a lot of work but it beats taking it all down.

RE: Garden drainage

First, since it's a garden, make sure the soil percolates decently by adding composted organic matter if necessary (to 10-12" depth.) Then, make sure that the grass area--especially the lower elevation portion--is not higher than the mowing strip (so that it would prevent water from running into the grass area.) Bring the soil level to its proper height (it looks good in the photo) and make sure that you don't create any depression in the soil surface at the lower end. You might crown the bed so that the soil is an inch or two higher at its center (running along the fence area) so that water is draining from the bed along its length. Then, add the bark in a uniform layer to the height of the back of curb. In the beginning, you might get a little washing of bark at the lower end after rains, but this should settle down after the bark has a little time to settle in. If the slope is greater than it appears in the photo and washing of bark continues, you might consider permanent plantings (perennials or groundcover) at the lower portion of the bed.

RE: Garden drainage

  • Posted by bahia SF Bay Area (My Page) on
    Mon, Jan 9, 12 at 14:20

It may not be the problem you think it is once you amend the soil properly with a good amount of organic compost, and plant it out. The first question to answer is how long it takes the water to disappear after a typical rainfall for your area. If it takes more than 8 hours, or even days, you do have a problem that double digging or heavy amending isn't likely to solve. I suspect in your case it is more likely the soil is just heavily compacted and doesn't drain well. If run-off from the driveway runs into this area, you may need to add a drain line to take it away. If it is just rainfall that pools here, it probably isn't a real long term problem. You don't way where you are located, or whether you know if you have a hardpan/caliche compacted soil layer in your neighborhood, nor how much rain you can get at one time. These are all things anyone would want to know before they can really address your issues.

RE: Garden drainage

If it turns out the garden does not perk very well you can always plant a bog garden.:)

RE: Garden drainage

a bio swale is a good option to consider.

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