>For example, I have noticed that the soil level in the oldest bed has gradually declined, probably because the soil was 1/3 organic and that part is breaking down (the soil is equal parts sand, pea gravel, and >planting mix). If I top-dress the bed with some organic matter, will that help to renew the soil, or am I kidding myself? >Any advice? Lots. If you pile sand and gravel on top of heavier soil, there will be a perched water table at the interface of the two media. Bulbs planted near the base of the raised bed’s slope will probably rot. If they are expensive bulbs, they will certainly rot. A long dry well, a trench filled with stones, at the base of the raised bed, would probably help with that. I built a raised bed of sand and gravel, here, some years ago. The bed is six meters long, three wide, and about forty centimeters high at the highest point (not high enough). I usually make raised beds with a “backbone” of old cinder blocks, pieces of concrete, old tires, etc., but in this case I did not. After I had raked out the bed into a shape I liked, I noticed that the sand reeked of diesel fuel. The smell didn’t go away after a couple of weeks, and I thought the horticultural value of diesel fuel was probably negative, so I added a couple of small bags of organic matter and some Yum Yum Mix. I figured that microbes would take care of the smell; within a couple of weeks it was gone. The organic matter is still there, surprisingly; I wish I hadn’t added it because it aids in rot, especially in the winter. And there is a perched water table at the base of the bed. I’ve been able to grow a few things successfully in this raised bed: oncocyclus iris, Iranian alliums, but only if they are planted higher up on the slope of the raised bed, and not in any of the organic matter. In this very, very different climate, the raised beds of gravel (with a little sand) are wetter than the raised beds of clay. Relatively wetter. They’re the only which even remotely resembles a “moisture-retentive soil” here. The top few centimeters in the gravel are dry, to be sure, but any rain which falls infiltrates the gravel quite easily. Rain (such as we have, which isn’t much) just bounces off the clay. The raised bed of pure clay here has grown juno irises quite well, especially the ones which stupidly insist on emerging in January. The bed is bone-dry except in spring. Bob Nold Denver, Colorado, USA (not really in Denver, but in its western suburbs, in the rain shadow of Mount Evans) <HTML><HEAD></HEAD> <BODY dir=ltr> <DIV dir=ltr> <DIV style="FONT-SIZE: 12pt; FONT-FAMILY: 'Calibri'; COLOR: #000000"> <DIV> </DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'> <DIV style="FONT: 10pt tahoma"></DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>>For example, I have noticed that the soil level in the oldest bed has gradually declined, probably because the soil was 1/3 organic and that part is breaking down (the soil is equal parts sand, pea gravel, and >planting mix). If I top-dress the bed with some organic matter, will that help to renew the soil, or am I kidding myself?<BR><BR>>Any advice?</DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'> </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'> </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>Lots. </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>If you pile sand and gravel on top of heavier soil, there will be a perched water table at the interface of the two media. Bulbs planted near the base of the raised bed’s slope will probably rot. If they are expensive bulbs, they will certainly rot. </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>A long dry well, a trench filled with stones, at the base of the raised bed, would probably help with that. </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>I built a raised bed of sand and gravel, here, some years ago. The bed is six meters long, three wide, and about forty centimeters high at the highest point (not high enough). I usually make raised beds with a “backbone” of old cinder blocks, pieces of concrete, old tires, etc., but in this case I did not.</DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>After I had raked out the bed into a shape I liked, I noticed that the sand reeked of diesel fuel. The smell didn’t go away after a couple of weeks, and I thought the horticultural value of diesel fuel was probably negative, so I added a couple of small bags of organic matter and some Yum Yum Mix. I figured that microbes would take care of the smell; within a couple of weeks it was gone. The organic matter is still there, surprisingly; I wish I hadn’t added it because it aids in rot, especially in the winter. </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>And there is a perched water table at the base of the bed. </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>I’ve been able to grow a few things successfully in this raised bed: oncocyclus iris, Iranian alliums, but only if they are planted higher up on the slope of the raised bed, and not in any of the organic matter. </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'> </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>In this very, very different climate, the raised beds of gravel (with a little sand) are wetter than the raised beds of clay. <EM>Relatively</EM> wetter. They’re the only which even remotely resembles a “moisture-retentive soil” here. The top few centimeters in the gravel are dry, to be sure, but any rain which falls infiltrates the gravel quite easily. Rain (such as we have, which isn’t much) just bounces off the clay. </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>The raised bed of pure clay here has grown juno irises quite well, especially the ones which stupidly insist on emerging in January. The bed is bone-dry except in spring. </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'> </DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>Bob Nold</DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>Denver, Colorado, USA</DIV></DIV> <DIV> <DIV style='FONT-SIZE: small; TEXT-DECORATION: none; FONT-FAMILY: "Calibri"; FONT-WEIGHT: normal; COLOR: #000000; FONT-STYLE: normal; DISPLAY: inline'>(not really in Denver, but in its western suburbs, in the rain shadow of Mount Evans)</DIV></DIV></DIV></DIV></BODY></HTML> _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/…