We had a MAC growing up & on our old garage roof that did the same thing - one year there were green weeds growing! Our roof is tar & gravel, but that is the replacement roof. When we moved here no one used the garage because the blackberries had made soil on the roof, rooted in it, and the roots had penetrated the roof eventually, and were hanging down inside of the structure! Isn't Mother Nature amazing? That's what I say to those who worry about the exact type of compost & fertilizers to use (not on top of buildings) - if you leave the leaves, plant food and compost magically appear - ever noticed how forests & jungles survive w/o humans running around spreading compost & fertilizer? Jackie

I couldn't disagree more!! Potting soil or soil suited for growing in containers has very different requirements than soil necessary for inground growing conditions. This is primarily because container culture is a closed environment requiring frequent, often daily, watering, offering a limited root run and with a need for exceptional drainage. Too much organic matter (in the form of any kind of compost) will eventually adversely impact drainage, as it continues to decompose and compact, reducing pore space. The best container soils generally contain no real soil and very modest amounts of OM. Peat or coir (cocoa fiber) is a good base (yes, they are OM but very slow to decompose) and you do need the addition of pumice or perlite to facilitate drainage and provide porosity. High fired clay (Turface) is a great substitute for these if available in your area. Bark fines will help with moisture retention plus provide necessary texture and pore space. Check out the Container forum for many excellent DIY potting soil recipes, especially any of the posts by Al (tapla). If you have access to Gardner and Bloome products, look for their Blue Ribbon Potting soil. I've used this product for years and it is an excellent medium for any kind of container growing, especially for long-term containers, which can be a challenge to maintain with quality soil conditions and fast drainage.

Here's a real fast and quite possibly not entirely accurate description of "soil." Half (50%) of most soil is air or water, in a constantly changing proportion between 'dry' and 'saturated'. Both air and water are usually in plentiful supply in most gardens. Of the other half (50%) of soil, most of it (roughly 40-48% in most gardens) is made up of minerals formed from rock. In the form of sand (big particles) silt (smaller particles) and clay (smallest particles.) And just like air and water, rock-based minerals are usually in plentiful supply, in most gardens. If you want to make the soil you have better for growing food, add lots of varied organic materials. You can do this by sheet (lasagna) composting inside your raised bed; or you can compost in a separate bin and then add the finished compost to the bed; or you can grow green manures inside the raised bed, which can help break up the soil (and subsoil) for future food gardening. Or, you can try variations on all three. From the limited description you gave, this is what I would do. 1) Add as much leaf mold as you can (up to 6" deep) to the surface of the raised bed, as soon as you can. Then toss as much used coffee grounds on top of it as you can (up to 2" deep.) Then shallow-till those materials (4-6" deep) into the existing topsoil. 2) Two weeks later, plant a fast-growing leafy green manure crop (like clover, peas, or other legumes) which will break down quickly to increase nitrogen. Grow it for three months then cut it down (leaving the debris right where it falls on the garden bed) and then dig it under -- or smother it with cardboard or newspaper. 3) While the green manure crop is growing, make a couple cubic yards of compost with whatever other compostables you have on hand. 3) Then two weeks after digging the green manure crop under, plant another crop for extensive root and stalk growth. Something which will winterkill could be best; rye or even wheat could work. Buckwheat also produces a lot of organic materials in a short time. 4) Before the 2nd green manure crop goes to seed, chop it down and leave the materials on the ground. Water it, cover it with thick layers of newpaper and/or cardboard, top off with the compost you've made -- then plant your veggies in the fall or the following spring. Something to remember about organic materials: they decompose. In the process, they reduce dramatically in size and bulk. About 9/10ths of whatever organic materials you add to a compost pile, or drop right on your garden, will turn into gas within a year or less. That's nine parts out of ten. So: if you want to raise up the surface of your soil roughly two and a half inches, figure on piling up the organic materials roughly two feet high. It seems like a lot of work when you think of it in that way. However, the results of 2" of good compost applied to most soils can be spectacular. Combined with two green manure crops, you could see a very large increase in the percentage of organic materials in your soil. There's many FAQs about soil and composting here on the forum, which can help give you lots more information about all of this stuff. See the link, below. Good luck and have fun. :) All the best, -Patrick Here is a link that might be useful: Soil, Compost and Mulch forum FAQs

In all my years of gardening I never had 'enough' compost as I mostly gardened in cold climates and composting was a slow process. However, the single thing that made the most difference in the fertility of my soil was trench composting or burying kitchen scraps between plants. This not only decomposes quickly and adds fertility but it also feeds the earthworms who provide one of the best fertilizers available, which is worm castings. As long as I fed the worms my soil was fertile. Helps if you eat a lot of vegetables or can scrounge veggie scraps. I've gotten them from produce departments of 2 stores altho not all stores will allow this. Another important factor in improving soil fertility is to always cover soil with mulch, preferably one that will decompose fairly quickly. Mulching spring and fall worked well for me. I always used my 'not-quite-finished' compost as mulch, sometimes mixed with sawdust or shredded bark. Don't agonize over the process of composting, just do it as best you can and you will eventually have usable compost.