Best in what sense? Without knowing whats growing in them, how often you can water and all that I can't really say what is best because, well, best is a subjective thing.

All 3 of the mixes you listed are peat based mixes so they all have the same strengths and weaknesses.

Given the large size of your planters a loam based, rather than peat based mix might be your best choice and a large container is much like growing in the ground. The loam based soils are very heavy so forget about moving the planter, but it probably isn't movable even with a peat based mix.

Long story short is the peat based mixes break down over time, soil volume shrinks and repotting or at least topping off is necessary. So, think loam based mixes for longevity if reppotting a large container is an issue.

Anyway, I and others could give you better recommendations if you could indicate what is important to you (other than growing nice plants) such as how often you can water, fertilze, what kind of plants you wish to grow etc.

Growing in a 2x2x8 container is almost the same as growing in a 2x2x88 container is almost the same as growing in a 2x2x2 container, and 2 feet isn't particularly deep. So, just because your container is long, it doesn't mean the soil needs to be earth mineral (dirt/loam) based like you would use in a larger, deeper container. For the record, I agree that loam can be used with good results in very large containers, but I would reserve its use to those that are deeper than 3 feet & hold a yard of soil or more. Discussions about soils for large containers often fly in the face of what you think you've learned about container growing, but I don't think the size of your container(s) fit the need to get into that discussion.

I too, think that you're short-changing yourself by limiting your choices to a commercially available mix. The structure will fail inside of 2 years and you'll be saddled with the problem of changing the soil or living with compaction.

If you decide you'd like to build the soil, I'll send you a photo of the soil I have in my raised beds. It is a mix of pine bark, peat, swimming pool filter sand, crushed granite, and Turface (a baked clay granule). The soil is 5 years old and yields fantastic growth and offers great aeration and superb drainage with very good water and nutrient holding ability. I've done nothing to it since building the beds 5 years ago aside from side-dressing the plants in it with Milorganite periodically. The only component that would take some searching is the Turface, but there will be several places near you that sell it. The components are all inexpensive & the soil will likely end up costing the same as or a little less than the commercial mix you're looking for.

The soil could easily be tailored to the plant material you select by simply varying the mixture.

Disregard my post if you're decided on a mix from a bag.

Good luck. ;o)

Al

Thanks username & Al,

I plan to plant a blend in the planters. Probably evergreen shrubs, perennials, annuals, and perhaps some ornamental grasses.

I am interested in creating my own potting medium, but have some concerns about my ability to do so. I want to plant within the next week or so, and am worried that I won't have the time to make my own mix properly, having never created my own mix before.

Also, since I am in the city, there's not much available if it is not offered by Home Depot or Lowe's. I do have a car, but it is a small sedan and at least bagged potting mix is, well, bagged.

I'd really love to try. Am I up for it? How challenging will Turface be for me to find?

I would really like to not have to worry about replacing spent mix in a year or so. I want to learn and expand my skills, so would love the photo you offer Al, and any other advice.

Many thanks,

CarrieB

Do you see yourself transplanting the evergreen shrubs? If not then I would think of a more permanent potting medium. Ground soil is mostly inorganic so it doesn't 'shrink' over time. Any mix that is primarily organic based whether it be peat, bark, compost or whatever is going to break down and require replacement eventually.

So, you can start with a loam(soil) based mix and not worry too much about replacing it OR

Use an organic matter based mix and see how simply adding an inch or two of compost each year does for you. Lots of people make semi permanent plantings in containers and simply add compost to top off things each year.

You really just need to make up your mind about how willing you are to replace the mix and transplant vs. topping it off as required to maintain volume.

Your plants will grow 'well enough' either way, but as Al would say you have to decide if 'well enough' is good enough for you ;-)

I remember quite a while ago--many years ago--I found a bag of Promix. I was struck by how good it seemed. I wrote to the manufacturer, and they said they were located outside of Philadelphia, somewhere west if I rmember. I have never found it here, so can not comment about it. (They sent me a magnetic sales piece, which I just found on the side of my refrigerator. Some sales pieces are of lasting quality!) If I remember correctly this contained product contained vermiculite, perlite, and other products. They are in my own mix, which I feel is important. You might visit their plant and find out information of your own. One thing I have found is that I like a gritty feeling mix, and I use pool filter sand, which you can locate locally. I use about 20 to 25% pool filter sand. You will have to experiment. If you are going to mix your own "soil"--and you can do it--I'd recomment you purchase one of these blue tarps ( 6' X 8' would be large enough) to mix the soil on. Spread the unmixed products on it, lift up one end, then fold it over the pile that results, and pull it until it is well mixed. Do this several times until you see that it is well mixed. A couple of more things. IF you have a bottom to the units you are constructing, line it with newspaper--at least 10 sheets thick, preferably without colored ink, and not the glossy inserts stuff. You can also add shredded newspaper, seaweed if it is available to you, baled hay(spread it out), leaves, anything that will decompose. If you add these, be prepared, in the Spring, to add additional mix. If you can stand the smell--temporarily--get some cow(best) manure, horse, or sheep manure and add a two inch layer before you put the last two inches of "soil" before closing it up for the winter. That will do wonders for the plants next Spring. One last thing, not everyone is content looking at mixes that have the white perlite showing, so leave some room at the top where you can add some garden soil from your garden, or compost, with, again, some pool sand. (pool sand is the best, and sure beats regular, or washed, sand from a "sand pit". Please remember, the work you do now will provide you better results next Spring. If I can help you further, do not hesitate to e-mail me.

Hi, Carrie. You should have the photos I sent of the 5 year old soil in the raised beds. I guarantee a peat soil will not look like that after 5 years. ;o) If you decide you'd like to "go for it", I have contacts in Philadelphia that will provide me/you with a source for the materials (already made the call).

A tip about "topping off" containers that have settled. If the containers have perennial material in them, it's likely going to be sensitive about about planting depth. Topping off can introduce rot organisms to herbaceous crowns or attack the bark of woody perennials (trees/shrubs), which in effect (exposes cambial tissues) girdles them.

Because the soil I am suggesting you use is more than half inorganic and the organic component, pine bark, breaks down at a snails pace when compared to peat, settling should be pretty much a non-issue.

Whatever your decision, you are wished well.

Cheers.

Al