Dawn R
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Sunken Garden Beds

I live in draught ridden Southern California and the more I water my garden, the more I feel I should be seeking a water conscious alternative. I am a newer gardener and am giving thought to doing a sunken garden bed next year. (

I would appreciate hearing the pro's and con's as well as any tips to a sunken garden you may have.

We have clay soil, hot/sunny weather, somewhat limited space, and we get Santa Ana Winds.

Thanks for the insight

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rainbowgardener
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Re: Sunken Garden Beds

I imagine you won't be able to keep pouring water on a garden. Didn't California just [finally!] impose water restrictions? That is only going to get more stringent, not less. So definitely ethically and legally you need to be finding drought conscious alternatives.

The typical thing that is suggested is xeriscaping - landscaping with desert adapted, drought tolerant plants.

Here's a couple posts I've done on xeriscaping, with pictures and links:

https://www.helpfulgardener.com/forum/vi ... ng#p349896

https://www.helpfulgardener.com/forum/vi ... ng#p326461

https://www.helpfulgardener.com/forum/vi ... ng#p313418

Living out here where water just falls from the sky (as it is right now), I never heard of sunken gardens. But I looked it up and it does sound like a recognized solution for drought areas.

https://az-heirloomgarden.org/heirloom_g ... nBeds.html

Seems like it would have to be done carefully though. The article mentions clay soil and letting your beds have standing water for awhile until it percolates down. A lot of drought tolerant plants could not tolerate that. So I think you would need to punch some drainage holes in the bottom of your bed (like with a garden fork), so the water doesn't stand too long. And I think you would need to choose your plants carefully. Look up rain gardens and plants for rain gardens. It's a thing folks out here do to capture rain, not let it run off. But they have the same issues about having standing water at times and totally dry at times. So you need plants that tolerate both.

A quick beginning of a search turned up a couple plants for you: thrift sea pink (armeria maritime) Light Requirement: Sun Soil Moisture: Dry , Moist ; western columbine (aquilegia Formosa) Light Requirement: Sun , Part Shade Soil Moisture: Dry , Moist .

So that's the kind of thing you would be looking for, native plants adapted to your conditions, that can handle being wet and being dry. Note in the article it mentions being sure to provide some shade for your garden area.
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digitS'
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Re: Sunken Garden Beds

I have no experience and not much insight ...

I think you should be prepared to remove quite a lot of sub-soil, Dawn R. Loosening soil puts air into it, fluffs it up and the soil surface ends up several inches above where it once was. Add a couple inches of compost and there, you've raised more.

So, double digging must be required ... unless you have an abundance of topsoil and can afford to just move some of that and dump it elsewhere.

Sub-soil, could be mounded on what will be the paths, leveled and trodden upon. Topsoil can be returned to the trench and also used for a bit of edging. The excavator can return to the lawn chair but may need help at sundown to trundle off to bed.

Here is an old photo of Zuni gardens and a LINK to a Zuni Youth gardening program.

Steve
zuni_gardens3.jpg
zuni_gardens3.jpg (54.67 KiB) Viewed 1919 times
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applestar
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Re: Sunken Garden Beds

Like others I have no actual experience with sunken gardens except maybe the little rice paddy raingarden I made. But here are some more thoughts --

You could probably consider digging "swales" or incorporating the theory if your garden is on any kind of slope.

My postage stamp property is nominally flat but is graded as is typically, so that water will flow "away from the house." I built rain barrel overflow rain gardens at the base of two of the main roof rain gutter downspouts and another one where the grading of my property and neighbors property creates a "gully effect" and where the previous owner of that house purposely extended the rain gutter to drain away from his property and basically wash down along the property line on MY side. :?

Other downspouts have been supplying water to existing trees and shrubs so I can't sequester the water, but I've been making shallow swales and channels to direct some of the water.

If you have a drain for your air conditioning or dehumidifier that comes out of the house somewhere, you may be able to take advantage of it. Grey water system would be a more advanced concept.
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ElizabethB
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Re: Sunken Garden Beds

Hi Dawn, welcome to the forum.

When you say garden are you talking about ornamental gardening as in landscaping or are you talking about vegetable gardening?

If it is landscaping then DITTO RBG - Xeriscaping is the way to go. When done properly it is drought tolerant, low maintenance, low water consumption and strikingly beautiful.

My Brother and SIL live in Erie, Co. Heavy, clay soil, little precipitation and strict water restrictions. After a failed attempt at traditional landscaping SIL opted for xeriscaping. She consulted with her County Agent, did a lot of research and hired a landscape contractor to assist her with the overall design. Brother and SIL did the installation. The result is a stunning landscape appropriate for a home with a view of the mountains.

Another option would be a Japanese style garden using drought tolerant plants. Japanese gardening is a minimalist approach. Less is best. Few plants are used and there is an emphasis on structure.

On to vegetable gardening. Because of your clay soil I see a sunken garden as a nightmare. You will have extremes. Either a water pit or a dry hole.

If you want to grow vegetables I would suggest raised beds. If you start small and use an intensive gardening method such as SFG you can grow a lot of herbs and vegetables in one or two 4' x 4' boxes. Water your vegetables early in the morning with either a bucket of water and a cup or a watering can. No over head watering. Water only the base of the plants. Another option is container gardening. I find container gardening to be more expensive and more work than SFG.

Anyway - that's my 2 cents. :-()

Good luck

BTW - SIL wanted a vegetable/herb garden so Brother built 2 4' x 4' boxes with legs to create table height gardens. They are situated on their deck which has direct access to the kitchen. SIL is an excellent home cook and loves having fresh vegetables and herbs within easy reach.
Elizabeth - or Your Majesty

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When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant. ~Author Unknown

Dawn R
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Re: Sunken Garden Beds

Thank you for your replies. :-D I appreciate and your thoughtful replies. I'm going to have to think a lot more about this one before I go ahead with it :-/

I suppose I should have been a bit more clear. I was talking about vegetable gardening in a sunken bed. (The rest of my property is another issue altogether)

When clay soil is amended it is good for vegetables. I wanted insight into your thoughts on a sunken vegetable garden.

As I somewhat understand it, the bed is dug out (quite the task with clay), then the soil inside the sunken bed is amended with compost. The lower level of the bed helps protect from evaporation and wind as well as drawing water from the higher level soil.

I'm a bit apprehensive to build a permanent raised bed because they dry faster than being in the ground.

Right now, I am thinking about trying a small sunken garden AND a small raised wicking garden next year to see how I like each.

I can find information on wicking gardens, but sunken...

Dawn R
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Re: Sunken Garden Beds

Just read a better description of how a sunken garden works. It is suppose to also be near the base of a slope of some kind. I guess I'll be doing a raised wicking system since I'm on 100% flat land. Thank you once again all for the replies. If you have ever dug in clay you will know why my research is very necessary.

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ElizabethB
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Re: Sunken Garden Beds

Dawn . clay soil is a beast. Yes you can amend it and make it suitable for planting but the question is - is it worth the time, effort and expense?

For vegetables raised beds are an ideal solution to poor soil. Check out SFG. If you hand water - easy to do with one or two boxes - or use a micro drip system your water usage is minimal compared to a lot of other gardening systems.

Good luck to you.
Elizabeth - or Your Majesty

Living and growing in Lafayette, La.

When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant. ~Author Unknown

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applestar
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Re: Sunken Garden Beds

The kind I'm thinking of, which I think saw in Jeavons book (How to grow more Vegetables....), involved double-digging a rectangular bed, then instead of leveling it, you grade it so that it is higher on one end ...I think about a foot deeper than on the other end ... Maybe higher than the gound where highest -- you make your own slope?
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Dawn R
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Re: Sunken Garden Beds

Wow! That's a great deal of work for a garden. I think I'll just do the tried and true SFG or a wicking bed.

It is an interesting idea to think about hydrologicly though; build a graded hill/ sunken bed to be watered by it.

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applestar
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Re: Sunken Garden Beds

So a quick glance at searched images at "wicking beds" -- they look like giant sub-irrigated planters / self-watering containers like Earthboxes and other DIY... Except there is no specific deliberate attempt to create an airspace between the reservoir and bottom of the soil.

Is there no chance of stagnant water accumulation? Anaerobic water/soil is not pretty and get rather stinky, not to mention possibility of fostering malignant microbes.
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imafan26
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Re: Sunken Garden Beds

Another choice to create a keyhole garden. It was designed for use in Uganda where water had to be hauled 2 miles daily. It uses gray water and has a built in compost bin.

You can use a metal cage for the center and if it is mounded and mulched, it will retain water longer. I also help to choose drought resistant plants.

The keyhole garden is 6 ft in diameter. and water, kitchen scraps and browns go in the compost bin and percolate into the garden to keep it watered. 6 ft is the maximum size since water does not go out much farther from the basket.

Mulching and adding a frame to put on a summer shade will help some plants weather the summer sun better.

https://www.youtube.com/watch?v=ykCXfjzfaco
https://www.inspirationgreen.com/keyhole-gardens.html
https://ucanr.edu/sites/scmg/files/183771.pdf
https://www.bountifulgardens.org/Drought ... ments/344/
https://nudgeblogt.files.wordpress.com/ ... torial.pdf

Adding a lot of organic matter, mulching and deep watering will help your plants retain and resist drought longer.

At my community garden, the plants there only get watered once or twice a week unless it rains. If your plants are trained early on, not to expect a drink every day, they learn to adapt.
Happy gardening in Hawaii. Gardens are where people grow.

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rainbowgardener
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Re: Sunken Garden Beds

Elizabeth: Re- "For vegetables raised beds are an ideal solution to poor soil" That is true in Louisiana and where I am in Ohio. One reason raised beds work well for us is that they improve drainage and in winter the above ground soil warms up faster.

Dawn is right that in hot, dry, drought tormented SoCal, faster draining and warming up faster, drying out faster is the opposite of what she wants.

But I don't know about sunken veggie gardens. Finding veggies that tolerate standing water and drought sounds difficult.

I think very important for you, Dawn, will be WHAT you grow and WHEN you grow it. As for marlingardener (mod here, look for her posts) in TX, tomatoes for example will not be a summer crop for you, would require way too much water and don't handle heat much above 90 very well. But you probably can grow tomatoes spring and fall much easier.

Look for desert adapted, drought tolerant varieties of whatever you grow. Nativeseeds.org has a catalog of heirloom, ancient varieties of desert adapted seeds:

https://www.nativeseeds.org/pdf/seedlistingcatalog.pdf

Here's a little more reading about drought veggie gardening:
https://www.treehugger.com/lawn-garden/h ... ought.html
https://ucanr.edu/sites/scmg/files/183771.pdf DROUGHT-RESISTANT CROPS AND VARIETIES
https://www.bountifulgardens.org/Vegetab ... ducts/346/ (another catalog of drought tolerant vegetables)

Thank you very much for being thoughtful about the water situation. One piece of how we got in this mess was people just thinking they could do whatever they wanted where ever they wanted. I grew up in Southern Calif. (Anaheim) 60 years ago. I remember getting up every morning in the summer and watering our lawn with the hose (back then ordinary people did not have irrigation systems). Now I know that was nuts, but 60 yrs ago I was 8 yrs old and my parents were making the decisions. It took all of us way too long to realize we live in a finite and fragile ecosystem. I'm very glad to see people like you trying to figure out how to live within it.
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Dawn R
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Re: Sunken Garden Beds

On a cursory look I really like the keyhole garden idea. I will definitely give it some contemplation. It's like what I do now to the max. I have a in ground amended garden with a worm tower. I think when I am ready to build something more permanent I will have to consider a keyhole garden.

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rainbowgardener
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Re: Sunken Garden Beds

Still it will matter what and when you plant. You really need to look for heat resistant/ drought tolerant varieties of whatever you want to grow.
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ElizabethB
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Re: Sunken Garden Beds

DITTO RBG on selecting region specific, drought tolerant varieties of vegetables.

SIL waters her table top boxes with a watering can. Watering only the base of the plants. Her "mile high" climate is arid, has persistent winds and high temperatures in the summer can be higher than in the deep south. SIL is a scientist (as in 2 PHD's and multiple certifications) and an avid preservationist. She is very pleased with low water usage and ease of working her vegetable garden.

She does use Mel's Mix. She maintains a compost bin and purchases peat and horticultural vermiculite when needed.

DO get into composting.

I had a kind of crazy thought. :!:

Typical SFG boxes are 6" - 8" deep. The bottom is lined with contractor grade, woven, landscape cloth (not the cheap felt like stuff you find at big box stores)

Dig down no more than 1" into your native clay soil. Line and build your boxes deeper - like 12". You will create a "water pan" beneath your boxes. Not so deep that it retains huge amounts of water.

:eek: Crazy but that is what you get when a gardener is presented with a problem!

I am really looking forward to hearing more from you. Keep us updated on your decisions and your progress.

Good luck
Elizabeth - or Your Majesty

Living and growing in Lafayette, La.

When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant. ~Author Unknown

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ElizabethB
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Re: Sunken Garden Beds

-wall- I forgot :!:

Use raised beds and MULCH :!:

Pine straw is the absolute best for water retention and weed control.

You do need a thick layer to start - 12". Pat it down around your plants then let it compact with time. The needles twine together creating a very effective weed barrier while allowing water to flow through and at the same time slowing down the evaporation process.

It decomposes slowly minimizing replenishment.

Contrary to popular belief it does not have negative impact on your soil pH. Pine straw is the ONLY mulch I use and I do have periodic soil test done.
Elizabeth - or Your Majesty

Living and growing in Lafayette, La.

When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant. ~Author Unknown

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rainbowgardener
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Re: Sunken Garden Beds

Absolutely second that about the importance of mulch, one of the main purposes of which is to conserve soil moisture. Very ingenious, Elizabeth's idea of creating a water reservoir. Turn your whole bed in to like a giant self watering container, and yet nothing is standing in water!

Re the mulch for veggies I like to do a green/brown mulch (where "green" and "brown" are used as in Composting, see the composting basics threads at the top of the Compost Forum). So you want nitrogen rich materials like grass clippings, pulled weeds and carbon rich materials like the pine straw, regular straw, fall leaves, shredded paper, mixed or layered. Make a good thick layer of mulch, like 4" or so of it and renew when it starts breaking down and disappearing. The green/brown mix makes a more complete compost for feeding the soil when it breaks down.
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Dawn R
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Re: Sunken Garden Beds

Thanks for the wonderful ideas. I try to choose more regionally appropriate species of veggies and sometimes omit water hogs. I try to strike a balance between my personal wants and the regional realities. Thank you SO MUCH for the link. I do find it hard to tell which veggies are a good idea around here.

Where mulch is concerned: I have had the WORST luck with pests in my mulch. House flies in particular, but also some kind of still unknown pest (I suspect cucumber beetles). I tried and pulled up 3 separate types of mulch and every time one went down the flies and pests returned in droves. (Bye bye baby zucchinis)

The sad reality of our dry heat is that the bugs are drawn to any moist space like mulch and there are few of them. I even have a garden lizzard living in the bush 2 feet from the garden who comes to snack on the bugs. However, Mr. Tail and my fly trap are not nearly enough to keep the flies drawn to the mulch in check. I love the idea of mulching and I do keep it under my orange tree, but sadly it is no longer going in my garden. If I mulch my garden, our entire back yard is unlivable and they find way into our home.

Composting on the other hand, I am giving thought to. I know there are supposed to be pest-free ways to compost and I love the idea. I do have a worm tower feeding my garden, but it can only take so much. I will have to figure out a compost situation soon.

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rainbowgardener
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Re: Sunken Garden Beds

wow, my climate is so different, I don't think of things like that. But what kind of mulch were you using? The word covers a lot of different possibilities.
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digitS'
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Re: Sunken Garden Beds

This may be of help.

I live in a semi-arid environment. There is less than 20 inches of precipitation, annually. Most of that falls during the winter months. It isn't really unusual to have no measurable rain during a summer month.

Rain or irrigation water moves quickly beyond the reach of most garden plants because there are hundreds of feet of glacial till beneath them - gravel. Adequate water for a compost pile can be a problem. For this reason, I've found that semi-subterranean compost piles are best.

They aren't that much work. I dig out an area the depth of a shovel blade, about 8". Since most of my gardens are in beds, I have often used the beds. So, the "trench" is the width of a bed. The trench is filled with compostables and the soil is returned as a layer near the middle and as a cap. It all decays quickly during the heat of summer.

If things were just left for complete decomposition, the soil would be close to being level again. If I was to move some of the soil elsewhere, instead of returning it all to the mix of compostables, the result would be a sunken bed.

Steve
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imafan26
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Re: Sunken Garden Beds

True in sandy soils, unless you add a lot of organic matter, water does not stick around for long.

But if you have clay and amend that with lots of organic matter, water will stick around longer.

In the keyhole garden, the compost bin in the center, not only provides nutrients, but also acts as a reservoir to hold and distribute water to the rest of the garden.

If you want to grow plants that need more water and you want to get the most mileage from the water you have then the SIP or earth box (self watering containers) do work very well. Watering with drip irrigation or subterranean watering with watering tubes are also possibilities. If you water the root zone the water does not evaporate as fast as when it watered on the surface. Mulching well also will help retain water in the garden longer.

It might be worth trying out a few things as some things will work better on some plants than others. I.e. tomatoes in earth boxes.
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Re: Sunken Garden Beds

There are many ways to be more water conscious. I haven't really considered a sunken bed, but there are many other things I do that help conserve water like use a rain barrel, gray water, and drip irrigation. Here is a link to an article that gives some more tips on how to conserve water in the garden:
https://gardendripsystem.com/15-things-y ... se-garden/
Hope this helps! :wink:

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