In the Garden:
Western Mountains and High Plains
February, 2012
Regional Report

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A good potting soil (left) is crumbly, airy and drains well. Garden soil (right) is too heavy to be a good choice for containers.

Good Vs. Bad Potting Soils

Spring is just around the corner and I'll be repotting many of my indoor plants soon. The begonias need to be divided, and the geraniums need to be cut back and moved to larger pots. Now is a good time to get prepared for these tasks.

Seems like an easy project -- but when it comes to picking potting soil, things start to get confusing. Some bags cost only a few dollars, while others are much more expensive. Some packaged products say there's compost in the mix and some have added fertilizers. All you want is to pot up some plants, maybe root some cuttings, and have everything thrive.

How can you tell if you are buying good potting soil? For most uses, I recommend a soilless mix, which does not have any actual soil in the bag. These soilless mixes are more lightweight to provide proper air and moisture around the root zone. Good mixes are pasteurized so as not carry any diseases or pests. The main ingredients usually consist of sphagnum peat moss, perlite, sand, finely shredded wood products, and compost.

I like to lift the bag and gently squeeze the mix inside. This can tell me a lot. When the bag is lightweight and releasing pressure allows the mix to spring back, that is a good sign. If the bag is heavy and the mix within squeezes into a ball and stays that way, I avoid purchasing the bag.

There are many potting mixes that contain fertilizer and water-holding crystals. They tend to be more expensive, but may be a help to those who don't fertilize on a regular basis or forget to water. I prefer to use potting mixtures without any extras since I like to control the amount of fertilizer myself and I'm fairly conscientious about watering.

I highly recommend that you moisten the potting mix before you add it to the pots. Otherwise, it is not unusual for the mix to float to the top when first watered. The peat moss that holds water so well will dry out if the potting mix has been in storage for a while. To moisten it, put the dry potting mix into a large tub, pour some warm water on it, and work the mixture with your hands to blend it together. Once it's damp, you can add it to the pots or other containers.

If you're potting mix dries out completely and shrinks away from the side of the pot, it can be hard to get moistened again by just adding water from the top. Instead set the pot in a tub with a few inches of warm water and let the mix soak up the water from the bottom. This may take an hour or so. Check by lifting the pot; when it is heavy again, the potting mix is properly moistened.

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