One of the Joys of Maturity
A Dry Sump for My Raised Bed
Even though I've installed a semi-raised bed for the Senior Garden, drainage is still a concern. Our raised bed is on gradually sloping ground, so only two sides of it really benefit from the raised bed effect. In wet weather, the center of the bed and the "high side" still can have standing water.
Our soil in the Senior Garden is clay. At about one foot deep, you hit a strata made up of some really nasty orange-gray clay that doesn't drain well. Penetrating that clay layer as deeply as possible with a dry sump drain helps dry out the garden in wet periods. The process is really pretty simple (and somewhat tiring). The short version is that you dig as deep a hole as possible with a post hole digger and fill it with coarse, builders' sand.
With the weather still nice outside and garden space opening up as fall approaches, I gathered my tools (rake, shovel, and post hole digger) and some sand and got to it. I've forgotten where I read about this type of drainage aid (maybe in Mother Earth News), but used it successfully to help dry out a perpetually wet spot just outside the back door of a house where I once lived.
If you have a persistent wet spot and like me, garden on heavy clay soil, the dry sump trick should help some. But don't expect it to be a wetvac or sewer. The improvement is only moderate. But for my rather large (16' x 24') raised bed, it may prove to be an ideal solution.
The terraced or "semi-raised bed" I mentioned earlier had its two other sides enclosed with landscape timbers to create a true raised bed a year after I wrote this piece. I'm not sure a 16' x 24' raised bed is ideal, but we've made it work for us. All the ones I've built since have been around 4' x16', easily workable from outside the bed.
The dry sump in the center of the bed does help dry the soil in wet springs, allowing earlier tilling and planting. It also tends to really dry things out mid-summer when our rainfall tapers off.
Since I've mentioned raised beds a lot in this piece, here are links to our methods of building raised garden beds.
at Senior Gardening