It depends on the mix, because just about all potting mix is "soilless". Miracle Grow is soilless, but has time release fertilizer in it, so in a way, it has nutrition. The problem is that organic/peat moss based mixes break down, and drainage worsens, making root rot a real problem. Using top soil is far worse, and is a recipe for disaster. It should never be used in any container, in any amount. Your choices are to either use a time release fertilizer, or fertilize at lower strength all the time, which is called a maintenance dose. Most fertilizers have instruction on how much to use.

Joe

If you don't want to fertilize often, then use a controlled release fertilizer (CRF) when you pot up the container. A common and popular brand is Osmocote. This should get you through most, if not all, of the growing season.

Soil-less potting mixes are pretty much devoid of any nutrients. And not even the addition of ferts to a mix like Miracle Gro would tempt me to use it. It is pretty much worthless for successful container growing.

Also these mixes are soil-less for reason. Adding topsoil, garden soil or even compost is going to compromise the container soil's ability to drain well.

Thanks very much for both of these comments. Although, Gardengal48, I have a question about what you wrote in the second paragraph. It sounds like soil-less mixes are better for drainage and yet you say that you would not use the Miracle Gro mix--is it the brand that is the problem? I am assuming that the MG potting mix is soil-less.

Thank you, Joe1980, for your helpful answer. Is Miracle Gro an "organic/peat moss based" mix? Is it possible to get another kind of potting mix and so avoid the potential root rot problem? Again, thanks.

Joe explains it pretty well, but with Miracle Gro in particular, it is the brand that's the problem. Of any of the widely available brands of commercial potting soil, it seems to have the finest and most uniformly sized particles of material. Combine that with the peat base and you wind up with an excessively moisture retentive, poorly draining soil. It pretty much turns to mush from the bottom of the pot up in a relatively short time. For any long term container planting it is completely worthless. And I am not alone in coming to that assessment :-)

One can find high quality, durable and textural packaged potting soils but they are not all that common and I'm not aware of any that have a very widespread distribution. Most tend to be from boutique type suppliers with a limited market area. These, like the mixes mentioned above, tend to be bark based with minimal components like peat or coir, if included at all.

Soil-less mix = usually mix of peat and very little perlite (white 'stuff').
Problem with peat is that it is either very wet (most often), or if you let it dry it could become as hard as brick; it is very difficult to re-wet.
If you look at bagged soil, read ingredients. Probably all you'll find contain a lot of peat.

For reference, here is a pic of the remains after I repotted a jade that I once bought. It was in a peat and bark based mix, with perlite added. I removed all the old soil and put it in gritty mix. Notice that what I removed from this poor plant's roots is a thick mud-like substance. Thanks to my daughters for letting me use their sandbox buckets for my repots.

Joe

You haven't mentioned where you are planting (inside/outside), what type of plants and what growing conditions you have?

I live in Florida, and use Miracle Gro for outdoor plants in containers. I mix some perlite and wood chips to increase drainage. My plants grow well and I need the peat to hold some moisture. There are other potting mixes sold which probably have less peat and might work better indoors, but I have no problems using Miracle Gro amended. I need the moisture holding capability.

It is important to explain what your planting plans are. Where are you growing?

Jane

Hispoesis - If your soil is appropriate, getting your plants on a solid nutritional supplementation program is monkey easy, which is why you'd do well to focus on your soils structure and stability, rather than its ability to 'feed the plant'. Some soils retain a 100% saturated layer of soil near the bottom of the pot. This saturated layer is devoid of useable O2, and is therefore a limitation. The more excess water the soil retains, the more limiting it is - there is no way to dispute the fact that soggy soils limit plants. In the same way that your ability to run a mile would be limited if you had to breathe through a straw, your plant's ability to carry on its business and keep its systems orderly is limited - no matter what is being grown in the soggy soil.

Miracle-Gro soils are well and widely known for retaining excessive volumes of water, so keep that in mind as you make your decisions.

Al