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Marie Iannotti

Gardening Question of the Week
Would Sunken Garden Beds Be an Advantage in Dry Climates?

By February 21, 2008

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Last week I wrote about raised bed gardening and I got an interesting response from Sara.: “Your recent article about raised beds, called to mind a question I've been pondering. In hot, dry climates such as So. California, what about sunken beds? Would they hold water longer so the plants don't dry out? I know in some areas such as AZ, the grass areas are somewhat sunken, then flooded once a week with water. They find that it saves on water usage while keeping the grass moist for about a week. I am referring to vegetable beds, here. What would be the advantages/disadvantages?”

I haven’t really been able to find any information on sunken gardens, other than for aesthetic purposes. Have any of you experimented with this idea or do you know of any resources we could direct Sara to?

Photo: © Marie Iannotti (2008) licensed to About.com, Inc.

Comments

February 21, 2008 at 1:42 pm
(1) Bill Raynor says:

Sarah,
I have found that planting my vegtables between raised rows in the garden in draught prone areas has improved production and made watering directly to the plants by flooding the improvised ditch a great advantage.The soil tends to hold the moisture better if the rows run north to south because they receive overhead sun only part of the day while the plants remain exposed to the rays.
Bill

February 21, 2008 at 1:47 pm
(2) Rock says:

If your walkways are recest and mulched thay water well.

February 21, 2008 at 6:09 pm
(3) Christa says:

Re: Coffee grounds. I used coffee grounds from Starbucks “Grounds for the Garden” program for several years. My orange clay soil has turned into a rich brown loam. Definately an improvement. Don’t mix the grounds immediately with the soil, it will take out the nitrogen in order to decompose it amd your plants will turn yellow. Instead, use it as a mulch and it will eventually find its way underground by the action of earthworms. Don’t worry about mixing small amounts into the soil when digging in new plants.

February 22, 2008 at 11:03 am
(4) M says:

1.

Sarah,
I have found that planting my vegtables between raised rows in the garden in draught prone areas has improved production and made watering directly to the plants by flooding the improvised ditch a great advantage.The soil tends to hold the moisture better if the rows run north to south because they receive overhead sun only part of the day while the plants remain exposed to the rays.
Bill

Comment by Bill Raynor — February 21, 2008 @ 1:42 pm
2.

If your walkways are recest and mulched thay water well.

Comment by Rock — February 21, 2008 @ 1:47 pm
3.

Re: Coffee grounds. I used coffee grounds from Starbucks “Grounds for the Garden” program for several years. My orange clay soil has turned into a rich brown loam. Definately an improvement. Don’t mix the grounds immediately with the soil, it will take out the nitrogen in order to decompose it amd your plants will turn yellow. Instead, use it as a mulch and it will eventually find its way underground by the action of earthworms. Don’t worry about mixing small amounts into the soil when digging in new plants.

Comment by Christa — February 21, 2008 @ 6:09 pm

February 22, 2008 at 5:29 pm
(5) B. L. says:

I visited a below grade water garden in Paradise Valley AZ. It was approx 8×8′ in back of a brick BBq..entirely of brick, with steps down from the patio. It had space for 2 chairs, a pond & trailing plants & ferns. since it only received Sun about 2 1/2 hours per day it was cool & pleasant.

February 25, 2008 at 2:48 pm
(6) Kate says:

Here in sunny Florida I have used raised beds primarily because of the poor soil (sand). But I found it really helps during the dry seasons.
Kate
Garden Tips 123

February 27, 2008 at 5:19 pm
(7) North Country Maturing Gardener says:

PLEASE try a Rain Garden! It is a sunken garden with a few extra additions. I am in the process of explaining how to do it on my blog found at
It’s a perfect solution for you!

February 27, 2008 at 5:37 pm
(8) gardening says:

I agree, rain gardens are wonderful solutions, in the right spots. Unfortunately, this is not an area where water normal collects or runs off and I don’t want to encourage it to. It became a problem because it was the only tilled area in an otherwise compacted lawn site. Prior to that, the water flowed far from my house, where it is welcome.

March 1, 2008 at 1:57 am
(9) RAYCHAEL says:

Hi Sarah,I have read some good somments,let me add:I live in southern California,south of San Diego. Here we have a layer of clay about 18 inches down[depending on how the property was graded when homes built].So,for me sunken is not an option..however,when you build a raised bed,if you double dig,then use 2″x10ft[width]xXft.[length]planks of wood,burying to a depth of at least 3-4 inches,water has no place else to go but down..especially if you keep the top of the soil areated,+[lightly mulched on top is a bonus].you can seal the side piece to the length with solicone[also used for aquariums].sunken gardens sounds great,yet a better concept to use where they have rock quarries for swimmimg![smile]
if lack of available earth to fill a raised bed and/or water retention is the issue;1.incorportate more amendments to the soil and 2.our clay/sand soil forms a hard crust when the sun evaporates the moisture on a daily basis..almost cement-like,so cultivate the area around
the plantings,encouraging the water to sink.Best of luck. Happy gardening,Raychael

March 15, 2009 at 2:05 pm
(10) PhoenixJen says:

It’s a great question. Sunken beds work wonderfully for hot, arid regions all over the world. Why?

–they create a microclimate that is naturally a couple degees cooler (just like basements are cooler than the rest of the house)
–they allow for the collection of rainwater
–they protect the above ground parts of plants from hot winds and the root zone from burning temps
–in many hot, arid climates, the soil is alkaline with high salinity. When salty soil is watered, the salts tend to migrate to the highest point – with raised beds, that’s the root zone – which just adds to the problem of growing plants in a hot, arid climate.
–sunken beds also attract more plant litter than raised beds thus naturally allowing for soils to build themselves up over time – something most deserts desparately need.

I’ve done sunken in vegetale gardens in Phoenix for a few years now and am really happy with the results. Even though my garden keeps getting bigger, my water bill doesn’t grow that much because I’m building soil and retaining water in my sunken beds. Oh – and no – my beds have never flooded out even in the heaviest rains because I’ve built good spongy soil so it just keeps on seeping in. Add a good layer of mulch and you conserve a lot of water and make a microclimate plants LOVE.

September 22, 2009 at 1:31 am
(11) randy says:

Check out nativeseeds/SEARCH. They have some pics of sunken beds at their seed farm in Tucson. nativeseeds.org

January 17, 2010 at 2:23 am
(12) Rachel says:

I live in Melbourne (Australia) in a very dry area on clay soil. I have a friend down the road who has put in sunken veggie beds this year and waters each bed once per week by flooding the bed. They also put shade cloth over the patch for very hot days. Thier patch looks much better than mine (which has raised beds) and the soil has much more moisture in it. This design also protects from some of the hot dry winds that blow through this area. I plan to put in sunken beds this year now.

January 19, 2010 at 1:47 pm
(13) Marie Iannotti says:

Rachel, it’s good to hear that sunken beds work with clay soil, too. I’m amazed how much sense this makes, yet I rarely hear about it.

February 10, 2011 at 7:44 pm
(14) Deborah says:

I live near Adelaide in S.A. and am very interested in sunken gardens. The advantages of catching more moisture and lower temperature sound good in this Mediterranean climate here. How to set it up so it wasn’t washed inwards was what I wondered about how to do. Apparently quite a few cultures in arid landscapes had sunken gardens used this method of lowering the garden bed. Would love to hear more on this and pictures and such. Cheers…

February 10, 2011 at 8:00 pm
(15) Deborah says:

Correspondingly – in winter I wonder if the lower temperature may not be a good thing since we get a bit of frost here.

November 13, 2011 at 9:29 pm
(16) Lynn P. says:

I have been thinking about sunken beds or “rain gardens” as some here have referred to. I planted some small fruit trees (very small) in my front yard, and I live near the coast in Florida. Sandy soil with poor nutrients. I have been building a soil “dam” around the area of the trees to hold in the water, as it runs off really fast when watering. I began thinking about just digging out an area and planting lower, instead. The rain will wash soil into the area from the sides, providing additional nutrients. It will hold water better as it is not in direct sunlight all the time. I plan to find out more about rain gardens. Ancient cities used to “terrace” their hills to maximize rain runoff for plantings, and probably also to increase planting area. Great topic!

November 14, 2011 at 2:20 pm
(17) gardening says:

A sunken bed sounds like it will solve several problems for you. I’d love to hear how it works out.

I’ve been involved in a couple of rain garden installations and keep meaning to write more about them. They were installed to help slow runoff and dilute pollutants from flowing into the watershed. It’s an interesting use of plants.

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