Printable View
Happy New Year all the best for 2008 to all!!!
I just finished my retaining wall project and I'm now ready to fill it with some small plants. The Garden bed measures 16.2 x .4 meters, How deep should I go with the top soil????. The fill currently is a clay soil, and I was going to use that mushroom compost topsoil.
Also The retaining wall is bricked and i was going to seal it with bitimun paint before i but the soil in, Do I have to seal it?? and if I do will the paint be enough??
I think around 300mm would be deep enough for plants, perhaps even first digging in a layer of gypsum to break down the clay to assist with drainage.
From my experience with mushroom compost I find it gradually breaks down and disapates having to be replaced after a couple of years so I think you would be better filling the area with sandy loam and topping the last 100mm with mushroom compost (if you really want) or even a thinner layer of mulch.
Other far more learned members will assist you with the wall.
Jacksin's on the money with digging in gypsum. If you don't break up the clay base you might run into drainage problems. Also your plants may struggle if/when their roots hit the clay subsoil.
When I did my retaining wall I incorporated gypsum, backfilled with an organic loam then put a layer of mulch on top. The plants are thriving.
Sandy loam in garden beds can be a bit too free draining unless the plants require a loose mix (e.g. succulents, cacti, lawn etc.).
One word of warning with mushroom compost - it can be very alkaline. If you're thinking of putting in any acid loving plants in the bed (e.g. camelias, azaleas, gardenias) I would advise against using it as a mulch or soil improver. A good organic compost would be a better option.