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Im in the process of planning my materials needed for my raised cactus bed. My only question is....is there a minimum depth? Im planning the bed to be 24" in depth. I want good drainage due to the annual rainfall in my area. Im planning to place Trichocereus Terscheckii, San Pedro, some fero's and other various cacti. I plan on finishing it before winter starts although no plants will go in just yet. Or....maybe I should go 12" instead of 24". Any input would be greatly appreciated.

You can get some rules of thumb from the "perched water table" designs that have been perfected for various types of sports fields. They can drain several inches of water an hour more or less indefinitely while still retaining sufficient water at all times to support the growth of grass. You obviously don't have such stringent requirements to retain water, but the idea of perching 12"-18" of your growing medium over a layer of much coarser gravel is still a good one. Sports fields lay pipes in the gravel to remove the draining water, but raising the whole thing above ground level is a much simpler solution. Don't just try to provide drainage by putting coarse material into a hole in the ground - that's called a swimming pool

Yea what your saying is true....it will be mounded as well for better water run off during heavy rains and help during the winter rains even though I will give some protection. So instead of 24" I will make it 12".

Cactus from desert/poor soil areas tend to have shallow roots that spread out so your 24 inched should be great. Raised beds are great but go light on the organic matter--I overdid it once (maybe 50% organic/50% non-organic and the cactus did fine but I had bumper crops of weeds the first 3 years until the organic matter got used up. I think now I would try something like 10-20% organic max.

If you think of some very big cactus you have seen growing in pots that were less than 24 inches high, your plants should be quite happy. Keep in mind, too, the cost--it takes a lot of material to fill a bed 2 ft. high by 3 or 4 feet wide and taller than 2 ft. would be proportionally more costly.

Yes I understand the cost in it but its something I always wanted and now that I have my own home Im prepared for it. Im planning it to be 8ft long by 5ft wide. Still debating on whether 12 or 24 in in depth.

Your home, your dream, your $$, I'd do 24"!

Yea 24" sounds better and safer considering the amount of rainfall we have in my area. The sandy loam I use and the NAPA I use is whats gonna cost the most I feel. Luckily the sandy loam is only $1.25 for 40 lbs. I can't get it any other way except buying it by the bags. The block I plan on using will run me about $200 for what I need.

Better than spending $200 or more on (soon to be) dead plants!

Agreed. It might take me a month or so to complete it but I want it to be done right from the start.

Glad to hear you are using block. Many people use wood, including redwood, and X years down the road it rots and they have to replace it. If you go the 24 inch you will be right on the edge for delivery. 3 cubic yards is too much to bother with hauling by pickup, quite pricey to buy bagged goods, and a little small to have soil trucked in bulk but you might want to shop around. Even if you have to pay a short load fee for having less than a dump truck load, it may pencil out well compared to other options.

Actually at first I was thinking of treated wood but as you said, down the road it would have to be replaced which would be hard to do. So decided stone blocks would be better and look great.

I've checked around. I can get a load of top soil that would give me more than enough for $50. But, its very rich and has some clay and is not a sandy loam. If I spend $50 on 40 lb bags of sandy loam I know exactly what Im getting. I can get pea gravel if I decide to use that in the mix cheap which I might do but it will be the NAPA....thats $12 for a 40 lb bag.

Been reading what everybody has posted. My native soil is very heavy clay. If I was to make a raised bed and wanted fast drainage, I would used 7/8" rock for the first 12" or so. I used that size of rock for my septic leach lines. Sixteen years and no sinking, backfill or drainage problems. Might save you some money too.

My thoughts exactly. I was debating on something like that. I was thinking of using gravel with mixed with SOME of my native soil for the first 12". I will have some large cacti such as San Pedro, Tercheckii, and a few others that I know the roots will go down that far and deeper.

for my front yard I want to do those humps you see in people's yards. I wanna make a smaller version of a raised bed. Since it will be a mount I am only going to mix native soil with maybe a load of dirt.. Im not sure. I gotta kill the grass first, but I will possibly add in the napa stuff.. I get 20 pound bags at Walmart for around 4 dollars. Last time I was there they had 6 bags of it, and I am sure if I talked to them I could get more. However I haven't really though much about that project.

Peterthecactusguy wrote:for my front yard I want to do those humps you see in people's yards. I wanna make a smaller version of a raised bed. Since it will be a mount I am only going to mix native soil with maybe a load of dirt.. Im not sure. I gotta kill the grass first, but I will possibly add in the napa stuff.. I get 20 pound bags at Walmart for around 4 dollars. Last time I was there they had 6 bags of it, and I am sure if I talked to them I could get more. However I haven't really though much about that project.

I was going to work on my outside garden during the holiday break, but the last two days almost 1.25" of rain. Heavy clay turns to mush. I was going to mix the Napa stuff with course sand more for looks since the garden has be established for 16 years.