SWC, the next level

joewormJune 1, 2011

Hi all,

I am wondering if Raybo's combo mix for SWC will work for a large SWC. I want to make a full size 4' x 8' raised bed with large reservoirs. Will that mix work for a large area?

Also would like to make the mix from scratch instead of having to purchase too many bags of potting mix. I would buy material in bulk to make the wicking mix. I'd like to make several 4' x 8' beds so I will need a lot of mix. Any ideas?


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rnewste(8b NorCal)


You are in uncharted territory on this. In theory, yes the 3:2:1 Combo Mix will wick in a 4 by 8 ft. SWC. But the devil is in the details. You will need to use multiple wicking baskets spaced no more than 2 ft apart, in my opinion. Also, how much normal rain do you get per year?

In a dry climate like the Southwest, you will need more aggressive wicking. In wetter areas like Alabama where you would get more rainfall, more restricted wicking will work. I know of a person who used a cattle feeding trough to fashion a SWC, so it can be done. But, a LOT of trial and error experimentation.

Frankly, I would start with a 3 ft by 3 ft. mock-up as a concept model and observe wicking and the optimal number and placement of baskets on a smaller scale.


    Bookmark   June 1, 2011 at 10:48PM
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engineeredgarden(7, nw Alabama)

If you have the room for a 4 x 8 raised bed, there's no way I'd even consider trying to make it one huge swc. Just make it 16" deep, and it'll give you excellent results. Because of the daily rain showers in your area, the mix needs to be quick draining.


Here is a link that might be useful: my garden is here

    Bookmark   June 2, 2011 at 8:55AM
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i have made 5 swc,s that are 100 gals with 12 4 inch wicks also works as the potting mix support. 30 gal water resvoir with 7 plus cubic feet of soil mix. heres my mix recipe for large swc.

3 parts shreded bark (pretty fine stuff)
3 parts peat moss
2 parts perlite
plus lime

i call them the (mother box)

1 holds 8 tomato plants and i use them for my giant pumpkins.

    Bookmark   June 2, 2011 at 9:37AM
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That's an interesting observation by you because I have done just that. I made a concrete reservoir, that's another story, that is 2' x 2' x 10" deep. On top of that I placed a 3' x 3' wood bed, 2x8 yellow pine, with what amounts to a 2' x 2' hole in it for the wicking material to get to the top level. The raised bed top cantilevers over the sides of the reservoir 6" on every side. The entire reservoir contains the wicking material which is nothing more than hardwood woodchips from some oak stumps that I had ground down. I used these chips last year in my first swc, a small plastic tote. I filled half of the tote with the woodchips and filled the rest of the tote with cow manure compost that I made. The compost was filled 2" to 3" above the top of the tote to form a mound and then the tote was covered with black plastic. I used a 1 1/2" pvc pipe for the fill. This worked great. I grew two hugh green peppers in that tote that produced an incredible number of peppers. I did not add any fertilizer to the compost initially nor did I add anything during the entire growing season. The plants got so big that at one point I pruned them back because they were getting too big, I thought, for that small tote.
Since I had such great success with that plastic tote and the woodchips, I decided to use the woodchips for my larger 3'x3' bed. I just put the 3'x3' bed together last week so it is too early to know if it will work out as well as the plastic tote. Time will tell. The issue with wicking material, is that I won't have unlimited access to woodchips, nor do I actually know at this point if the woodchips will work, and need to have something that is readily available and has a history of working for others that have used it. Hinse, the need for the 3:2:1 mix or some version of it.

Actually we get far less rain than you think until well into the growing season. We are usually in drought situations until mid June so I don't think a large SWC is overkill but I could be wrong. I will probably do one 4'x8' bed without the reservior to see how I like that.

What did you use for a container? Seems like the larger SWC will work based on your results.

Thanks all,


    Bookmark   June 2, 2011 at 1:05PM
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engineeredgarden(7, nw Alabama)

Joe, my garden consists of 19 swc's and 168 sq.ft. of raised beds, and I can tell you that doing both for a few years has made me wish the entire garden was only raised beds. The amount of cost and time involved in going with swc's is far less practical than raised bed gardening...just my personal experience...


    Bookmark   June 2, 2011 at 1:43PM
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How often do you have to water your raised beds?
16" deep seems to be excessive. Is there a reason your beds are so deep? What soil do you use in the large beds?
How do you fertilize the beds? Do you have to change the soil periodically or just add to the existing?
I have no experience in gardening so I need all the help I can get!!!


    Bookmark   June 2, 2011 at 6:52PM
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i use the 100 gal rubbermaid watering tubbs for cattle. last forever.

    Bookmark   June 2, 2011 at 8:48PM
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engineeredgarden(7, nw Alabama)

Joe, my largest raised bed is 25ft. long, 4ft. wide, and 14" deep, and I currently only have to water the plants every 5 days. (and it's brutally hot right now).
It's filled with 4 parts peat moss, 2 parts vermiculite, 3 parts compost, 1 part bark fines, and 1 part sand. This one bed will out-perform all others on the property - even the swc's.
I made it this deep to reduce frequency between waterings, increase drainage due to the drought -then torrential rainfalls, and also keep the plant roots cool when exposed to the sun's rays during the peak of summer.
The current soil mixture in this bed is in it's 4th year of service, and is topped off each spring with homemade compost. Fertilization is done by the recommended intervals by the local extension office.


    Bookmark   June 2, 2011 at 9:15PM
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How do you fertilize those big SWCs and how often?
How often do you have to fill the reservoirs?

Do you have an irrigation system set up to water your raised beds or do you water by hand? Part of the reason I'm interested in a large SWC is to keep from having to water constantly but every 5 days doesn't sound too bad.

Thanks for the help

    Bookmark   June 4, 2011 at 4:49PM
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for the tomatoes i mix in about 8 cups of a slow release fert,14-14-14. dolomite lime 4 cups per cotainer. later on in the season i can add a drip system into rhe fill tube using a 5 gal jug with fish emolsion. giant i.v.
water once a week.

for the pumpkins they will go through 10 gals of water a day. same fert, but i add a mycorhizal inoculant to the soil mix. its i.v. is a fertlone 9-59-8 drip.

    Bookmark   June 5, 2011 at 10:09AM
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