Raised Beds and Summer Heat

I have been SFGing over the winter here in Phoenix and have had excellent results! My beds are on saw horses and am worried that the soil may get too hot for the plants since the warm air can circulate around the entire bed (ie the bottoms of the beds are exposed since they are on sawhorses).

Has anyone experienced problems with this?

Thanks!

From what little I have read and seen here and elsewhere, the desert folks make deeeeep beds to protect from summer sun and heat.

Hopefully, someone helps more than I can. But, I can only imagine the exposure with a TT garden is huge in 100+ heat. Not to "refer away," but here is a quick link of pics I grabbed from google. I saw the same thing from a Vegas gardener a couple months back, and his were on the east side of his condo to shade from afternoon direct sunshine.

http://www.countrysurvival.com/big-box-square-foot-garden/

I only made it till may last year before the dogs ate my garden(Glendale), but my aunt's garden(Tempe) made it until Late July/ Aug. She had 6 in maybe 8 in deep beds and shade cloth. Then she stopped watering because they looked so bad and she figured they were all gonna die anyway. When I was over there in Nov there were a few tomato plants that looked to be still alive and started to "come back" , until that freeze around thanksgiving.

I'm not sure about TT boxes. I would suggest mulching the top of the bed to try and keep as much moisture in and shade will be a must when it hits 100 +. good luck and keep my posted. I was thinking of making my mother in law some tt boxes and would love to hear how they do over the summer.

By the way welcome to the forum! I love seeing others from AZ!

Last summer here in Virginia, it got very hot--high 90's and low 100's--for longer than I want to think about. I watered 2 to 3 times a day (misters, so total volume not that huge) and the plants that liked heat did very well. The ones that didn't care for heat bolted, or tried to, and I pulled them and ate. The lettuce was the one tender crop that lasted for much longer than I expected.

I don't know about TT's, either... but the earlier suggestions about mulch and shade cloth sound like worthwhile things to try. Maybe you could try to shade the sides of your beds to keep the soil cool?

Since this is my first year with Table Tops, and the fact that I live in a region where summer highs range in the high 60's and low 70's with an occaisional foray into the low 80's, I can't provide any experience.

I do know that some table top gardeners added heavy plastic to the bottom of their beds, with holes for drainage and they felt that would assist in keeping the Mel's Mix moist.

Hi Nate, I'm in Las Cruces, NM and have raised gardens and have had the same problem with the 105-110 degree heat and little humidity. I'm finding that deeper beds work well. I have one TT 6"deep and another 10"deep. Root veggies are doing much better in the 10" soil. I have to use more water, about a quart for each sq ft every other day. (We're on rationed water.) This summer I'm also going to try nailing sheets of heavy plastic to the four sides and let it hang down to the ground. Hopefully, that will help too.
Barb

What about putting some inch-thick insulation panels on the bottoms of the boxes?

I've lined containers of various materials with 3/4 to 1" of foam insulation -- the slab version from a hardware store, which comes in 4x8 white sheets, etc. This seems to save the roots from burning even in a metal ore tub.

I have a regular SFG I just put in here in Vegas and have been pondering various ways to keep the plants cool during the scorching months.

I'm thinking I might try one of those mylar survival blankets. I've seen ten-packs for sale and they seemed quite inexpensive.

Not sure how well it will hold up outdoors for an extended time, but I know it will reflect the sun's rays & heat quite well.

Course, I'll have to build some kind of supporting structure/cage to suspend it, but I had intended on adding that anyway.

I suppose the possible downside is that it also shades the plants. But I'm thinking most plants would appreciate having some down time when the sun blazes away 14+ hours a day.

Anyone tried using something highly reflective like this?

Gritman wrote:I suppose the possible downside is that it also shades the plants. But I'm thinking most plants would appreciate having some down time when the sun blazes away 14+ hours a day.

I haven't tried mylar, but believe me, your plants will want the shade. I had to shade my boxes here in Los Angeles last summer, and until I got a clue and did so everything was frying. I didn't put shade cloth over the whole box; just the top, so they were shaded during the hottest part of the day. The only plants that didn't seem to mind the heat were the pole beans and the okra (they kept producing like crazy).

I just used white muslin fabric since I already had it lying around. This year I might spring for shade cloth if I don't find something else already stashed.

Thanks, Coelli. I'm going to figure something out, that's for sure. I'll probably make a cage like in the SFG book. That way I can cover it or not, while still keeping the birds out. It'll take more money and labor, but I think the cage, if built properly, can double as a mini-greenhouse during the coldest months and during sprouting time in early spring.

My guess is that the height of your gardening season is not the summertime, though some plants thrive in the desert heat. Spring and fall would probably have different plant growing opportunities. A drip irrigation system and a thick layer (2" or more) of shredded bark mulch would help keep the soil temp down and retain precious moisture.

Several days ago someone (I think from Atlanta) posted a u tube of two guys from Arkansas building a greenhouse cover with 1/2 inch PVC conduit and using 3/4 inch PVC sections as the push on holders. I went out and got the stuff (cheap) and tried it with the idea of using it for summer shade. You don't glue it just put it together. It worked up to 35 mile wind with the plastic greenhouse cover.

johnp wrote:Several days ago someone (I think from Atlanta) posted a u tube of two guys from Arkansas building a greenhouse cover with 1/2 inch PVC conduit and using 3/4 inch PVC sections as the push on holders. I went out and got the stuff (cheap) and tried it with the idea of using it for summer shade. You don't glue it just put it together. It worked up to 35 mile wind with the plastic greenhouse cover.

Those types of set ups work great in cooler temps, but I would be very careful when the sun comes out and temps warm up. Even at lower temps, any sun will raise the temps under the plastic cover and quickly cook plants. You will for sure want to have a way to raise the plastic and vent it.

It will be an interesting experiment for your area. I don't hold to much hope for the high heat months down here in the SW corner of the state. I like the idea of the deep box gardens with the overhead built in. Will have to check my reclaimed lumber supply to see if I have enough for one. My current boxes are elevated beds about two feet off the ground and shallow at 5-6 inches. Am trying different things. My squash garden is in a 4' x 40' compost station made out of produce pallets and is 3-1/2' tall. Will be adding corn and beans to it shortly. Fall is the main growing season down here. Not much is planted until Sept. Sweet potatoes can go in until the middle of May and that is the last until the monsoon rains. Check out "Native Seeds" over in your area for types of plants adapted to our heat. Their varieties are for high and low desert gardening/farming. I will be using them extensively in the near future as my major seed source. Another plus you have are all the SFG growers in your area. I am kinda on my own down here and am developing a personal relationship with the county extension office. My biggest let down is when I found out that most of what I had planted in Feb. wasn't supposed to go in for another 7-8 months. Bummer. UoA has a site with good info for you too. Hope this helps a little.

Just musing here .. it may strike a cord with some of you who live in the oven .

Table tops why not make them self watering from underneath .
do it by adding a three inch deep floored tray covered inside twwith some pond liner so you have a sump and sit the table top on top of it adding a simple sock wick filled with peat to each square and nailed with galv nails on the bottom of the TT then add a filling tube that you can use a dip stick in & refill the TT with MM .

The under TT well should use less water than direct watering from above , it should also slow evaporation from above and drying out on the base and sides from hot moving air around the bottom of the TT .

Perhaps fill up with water jugs , hose or buckets once every few days or weeks .Check there is water in it each day till you get knowledge of how it consumes water in relation to the weather .

Wish Boffer was still active because he did just something like that, a self-wicking tabletop. Maybe you can find it in one of his threads. If I move in with my son, that's what's gonna have to happen with my tabletops. His inground self-wicking beds are working well, but I can't easily get down to plant in them.

Kay