Choosing Soil for Outdoor Ground and Potting Use

Posted by admin on July 7, 2009

Choosing the right soil for use in your ground or in potting is not easy. We have done extensive testing in our garden in San Francisco, California, to see what does and does not work. Most importantly, we haven’t ended up having favorite brands of potting mixes as much as a full understanding what will and won’t make a particular mix work.

When using a soil for plants and vegetables in the ground, you’ll see many choices out there. There is peat moss, compost, manure, redwood soil conditioner, seed starting mix, chicken manure, topsoil, potting mix, and the list goes on. Here are results of our tests:

• Planting directly in peat moss. First the peat moss needs to be soaked. Seeds can be started in 100% peat moss, but the mix does not offer many nutrients. It also acts like a sponge. To get plants and seeds to grow directly in peat moss, eventually I needed to fertilize. My suggestion here is to mix in peat moss for plants that need quite a bit of moisture or acidity.
• Planting directly in cow or steer manure. This can be done, but some plants will not make it, especially if it is too fresh. If it is aged some, it can grow plants but is better being aged as long as possible to cool down. The problem planting directly in this mix, even if aged, is that it can hold too much moisture and not drain well. My suggestion here is to use 1/4 of your mix as steer manure.
• Planting in “compost” mixes. Of course compost is great. The problem is that many bags of soil say they contain compost, but really they have shredded wood recently and added in a bit of manure and other matter. If you can see the mix before you buy, the more broken down it is, the better. There should not be large pieces of wood bark. These mixes can grow plants, but it is crucial to pick those mixes that really are compost. My suggestion here is to seek out compost and use it.
• Chicken manure. This is strong stuff. The only way to plant directly in this is to age it a long time. Still, though, it will hold too much water. My suggestion is to use this as a top dressing a few times a year to add nutrients to soil.
• Redwood soil conditioner. This is shredded redwood. It is good to break up tight soil. My suggestion on this is to use it in a very compact spot, such as the top or bottom of a plant just put in.
• General potting mixes. These can be good or bad. Look at the ingredient list, and ensure it has things like perlite, sand, manure, compost, etc.
• Topsoil. Often these are not great, but sometimes can be ok. Feel how dense and heavy the bag is. My suggestion is only get this if it has good nutrients in it and is not too heavy.
• Putting 1/2 of a pot full of steer manure and then a potting mix in the top half of the pot. This doesn’t work great, as once the roots get to the manure, it holds too much water and nutrients unless it has broken down further. My suggestion here would be mix manure in the bottom of the pot with compost or potting mix and then the top half of the pot with potting mix.
• Seed starting mix. These are sterile mixes with perlite, peat moss, and sometimes sand and another ingredient or two. They are good until the seedlings need nutrients. My suggestion is to use this only when starting seeds indoors.

I have tested and found the perfect mixes for pots and in ground for our use. Sometimes I need to mix together a couple mixes to make what I need.

For in ground use, I like a mix with compost, some shredded tree bark or tree material, a bit of sand, and manure. This mix gives good nutrients and drainage.

For potting use, I like to use a potting mix with compost, perlite, shredded fir bark, and some manure.

When I start plants from seed, I have found a regular potting mix to be good until I need to get more nutrients to the seedlings. At that point I transplant them into the mix in the paragraph just above this one. When planting, here is our favorite gardening trowel.