Raised Beds In Mediterranean Climate

I live in a hot dry Mediterranean climate (Crete) and made a garden with raised beds,  last year. In the winter it works ok but in the summer it's so hot and dry that the beds dry out so fast and I have to constantly water them. I notice the locals mostly do sunken beds, which makes sense now, and I want to try that next summer. My question is, would it make more sense to change my garden setup to permanent sunken beds, or do raised beds in winter and sunken beds in summer? Would sunken beds in winter get too waterlogged here? We get about 500-600 mm of rain annually.

I like the concept of a "volcano" bed, which is raised a bit around the edges, and sunken in the middle, plus lots of thick organic mulch blanketing any exposed soil inside. Depends a lot on your specific site conditions though, including slope, aspect, drainage, soil type/profile etc.

My preference is to edge the beds but not raise them. Then mulch heavily to retain moisture in the summer, and allow the mulch to rot down during the wet weather over the cooler months. Sunken beds would just get drowned here during wet weather.

My land is steep but terraced, so the land immediately surrounding each bed is level.

Mulch would help the beds not dry out so quickly.

If Sweet Alyssum will grow where you live it is excellent to use as a mulch and smells good.

Burra Maluca wrote:My preference is to edge the beds but not raise them. Then mulch heavily to retain moisture in the summer, and allow the mulch to rot down during the wet weather over the cooler months. Sunken beds would just get drowned here during wet weather.

My land is steep but terraced, so the land immediately surrounding each bed is level.

I have a feeling they would get drowned here too in the winter. What do you mulch with?

Alexandre,

The raised beds would dry anything in no time in my hot, arid, too sunny and windy foothill climate (I get 500 mm average precipitation). I have tried sunken trenches this year and they worked like a parabolic mirror reflecting even more heat to my plants. This year was a complete gardening disaster with cold spring and nothing germinating. When it became hot in summer I could see what the trenches did to tomatoes. Tomatoes normally do not want to produce and ripen in my place - due to too high temperatures and too intense sun, but they fared even worse by being torched by the heated sunken dirt. Mulching and twice a day watering did not help much. Pumpkins, zucchinis got all torched. Zucchinis normally produce a lot and I got only one [sic!] zucchini fruit this year. Next year I will just do flat gardening with gentle berms (10 cm max) around the plants.

Dareios Alexandre wrote:What do you mulch with?

Cut grass. We have a 'brush hog' to cut around the olive trees, which cuts the grass into fairly short lengths. We need to cut it anyway due to the fire risk so when it dries I rake up what I need and mulch with it.

Drip irrigation also works very well here.

I'm in central England, and we're moving towards what seems like a "continental Mediterranean" climate: hotter summers with 30-40C temperatures a lot of the time, and months with no rain, but frosts sometimes dipping to -10 C from Nov-May.

So I'm juggling conflicting needs for warmth & water retention (and still not forgetting slug management although there's not so any these days) too.  

I'm wondering if hugels would tend to dry out on the surface in our summers & suffer runoff.  I've always been suspicious of thick mulch harbouring slugs.

But perhaps a gentle wave of mulch at bed edges with embedded branch wood could retain moisture without the downsides? It could be drawn back from young seedlings, then drawn in as the plants matured, on otherwise flat beds?

Ac Baker wrote:I'm wondering if hugels would tend to dry out on the surface in our summers & suffer runoff.

some people do sunken hugels for that reason - bury the wood but leave the surface level, not raised, or even a bit sunken.

I've always been suspicious of thick mulch harbouring slugs.

The downside of a humid climate. Maybe that is going to be the silver lining for your hotter summers....

When I lived in California (in the central valley, which has been called an "extreme Mediterranean climate", I eventually had most of my annual veggies in raised beds edged with old roofing tin or cement blocks.  I was running drip irrigation on most things anyway, whether in the ground or in the beds, and so it didn't seem to matter much, the drip was going every day no matter where.  Mostly I used the beds to exclude the rapacious gophers....I had screen mesh in the bottoms of the beds to keep them out....otherwise they would eat every single root crop I would try to grow, even onions and garlic, and sometimes damage other things too.  Also some of the beds ended up with plastic in the bottom as well, to exclude the intrusive roots of some nearby pine trees which seriously colonized the beds after that irrigation water.  One or more beds would be completely dug out every year and re-filled....this provided the opportunity to place things like humanure compost, accumulated paper products, and the raked piles of half-composted mulch around the yard (gathered for fire suppression efforts) or from the animal pens (we had chickens and sheep and sometimes geese and goats).  So the raised beds were a win for me, because of three things...gopher exclusion, root exclusion, and organic matter incorporation; all of which only peripherally, if at all, have to do with moisture.

Similar climate here.  My raised beds have walls about 8 inches high, but when we built them, we dug the beds about 1 foot deeper and filled with quick rotting wood to help hold moisture.  With use and adding more soil, it's still only 8 inches high, but the soil goes down just over 3 feet.  

That little bit of raised bed at the top gives the advantage of drainage during the wet season, but the deep trench of soil makes it easier to retain the moisture.

The slug thing is real for UK raised beds. Thick mulch in a wet summer is basically an invitation. I've been compromising with straw mulch on the beds themselves and leaving the paths bare so there's less permanent cover nearby. Doesn't eliminate them but at least the population isn't living directly underneath where the veg is.

Arabic and Moorish cultures brought to Spain the method of growing on the berm in the wet season and the trough in the dry season. This can be done with terraces or swales. My strawberries have decided to use this method on their own as they spread from my hugels to paths that catch eroded soil.