2004 Newsletter Archive
Week 2 3/14/04
Let us talk about Potting soils today.
The major brands that I am aware are Miracle grow potting mix and Proven Winners Potting Mix. We also sell a brand we like called Canadian Gold potting mix. These are all very acceptable mixes for containers and baskets. I am sure there are other brands. The key is that in general when you lift the bag of soil mix it is generally light unless it is wet. All these mixes consist of Peat, Perlite, and Vermiculite. I would in general buy the cheapest mix since there is not much difference.
The problem with all the above mixes is that when they dry out they shrink. The other problem is that in the smaller quantities they are relatively expensive per cubic foot. One other problem is that they have two much lime in the mix for some plants.
We have found that if you add composted bark to the mixes this significantly reduces the amount of shrinkage. The only mix that I know you can get this in is commercial mixes that greenhouses use.
The greenhouse mixes usually come only in larger sizes 2.8 or 3 cubic feet.
Why our 3 cubic foot mix is best. We grow in this mix but just buy it in 60 cubic foot bags instead of the 3 cubic foot bags we sell you. We have specifically lowered the amount of lime in the mix to compensate for our hard water. Please do not use soft water on your containerized plants as the sodium is harmful. The best is rain water if you can collect it. In addition to this low lime feature we have had them add an organic beneficial soil organism that promotes growth and helps in root disease problems.
Please make sure the mix you buy has a wetting agent, a small fertilizer charge, and some lime. Our profession growers mix has all of the above plus the composted bark, a lowered lime charge, and the beneficial soil organism.
One other comment. The soil crystals that are supposed to help in the watering may keep the soil too wet especially if you are growing in the shade. They are also not very effective when you have composted bark in the mix.