Maybe some clarification would be helpful. ;o)

"I am thinking of substituting mushroom compost, or soiless potting soil or something else that would be more friendly when it is hot."

Substituting it for what? for peat? or is your intent to just use these ingredients to make a soil?

"Since the soil is draining, would there be any reason to try to amend the soil under the new soil?"

There is no way to tell w/o knowing what it is made of - how much water it holds - what likelihood there is of collapse before the planting matures sufficiently ..... Certainly, you want it to drain well, and you don't want it to be much different than any new soil you might add above the old. A homogeneous blend from top to bottom is better than dissimilar layers.

Media pH takes a back seat to irrigation water pH and alkalinity. Generally, if your media pH falls within the range of 5.0 - 6.5, you're not likely to encounter much in the way of problems unless it comes from your water. I decided a long time ago that chasing and maintaining any kind of pH stability in containers is more likely to be an exercise in futility than a success.

Once you have the ingredients in volume, the 5:1:1 mix should cost you somewhere near $5-6 for 4 cu ft, including the peat, perlite and lime.

Al

BTW - I didn't forget to address the water retention questions - I'll wait until I hear your reply before I comment on it more. Take care, Sammy.

Al

THe sphagnum (spelling?) peat moss is impossible once it gets dry, and I am afraid that in our intense heat, I could run into trouble with it. I am thinking of substituting mushroom compost, or soiless potting soil or something else that would be more friendly when it is hot.

Most soil-less potting mixes sold commercially are going to be mostly peat so that won't save you from it drying out.

Peat and bark both have the unfortunate quality of being difficult to rewet if they get too dry, but it really isn't a big deal. First, don't let them dry out! :)

Still, with heat and dry winds the top inch or three can go pretty dry, I understand that. The solution is to water twice. This isn't as labor intensive as you might think. You go to the first container and water it lightly and then move to the next and repeat. When all containers have been lightly watered you go back to the first and water more deeply. The idea is that you allow 15 minutes or so for the water to overcome the hydrophobia. After that the peat or bark will take up water readily.

The sphagnum peat moss has been at some point a monster to me. I remember digging down to see what was wrong, and seeing areas of hard sphagnum peat moss under a plant. I heard that it was bad to use in Oklahoma where we will have weeks of 100 degree or more temps.

Keeping the soil moist and watering twice are good ideas - I always water twice. I am glad you made that suggestion because in a given bed, I will lightly water then return to soak.

My problem is that the only way to see if you have watered sufficiently is to dig under the mulch on top, and go into the soil to see if it is dry or wet. I do that every so often. I am afraid that if I don't check regularly enough, I may lose everything I have in pots.

I can easily re-water top soil or compost, but if that sphagnum peat moss is dry, it is not that easy to moisten. My question was what would I use to replace the sphagnum peat moss?

I wondered about mushroom compost replacing the sphagnum peat moss since I use it in my rose beds. I suggested soiless potting soil since I used that before this year.

Also what is in the bottom of the containers is regular potting soil purchased from Lowe's. Since I think that only growing vegetables for a year at a time would keep the roots closer to the surface, I wondered if it mattered that the soil underneath was older soil. My pots are extremely large and the roots should never go down too far, so I am thinking I don't need to put anything down there before I add newer soil.

My potting soil bags say: "Professional Nursery Blend" and on the front in a bubble it says "Mushroom compost products". That is what we used last year, and the texture is like regular compost. It isn't like a block of sphagnum peat moss.

For what it's worth. All of our containers have holes in the side, and they don't "smell". You are lucky if you have always studied and then planted. I had a swimming pool effect once that cost me 12 Mister Lincoln roses. I was so proud of them that I dug out a huge plot and added pure compost - right on top of the hard clay. By the time I could smell them, I had killed them. Then I had to remove all the product, and add regular soil. (I forget the name of that product, but it was like mineralite magnalite - something I bought at a nursery.

That experience with the roses makes me appreciate good soil.

Sammy

I've begun using bark instead of peat in all my mixes.
I find it far easier to remoisten, and I find it drains far more readily than traditional potting soils.
In addition, the bark holds a good amount of moisture....but not for too long, which is excellent for root-health.

Josh

Sammy, I am having a bit of difficulty in following your comments.....it seems like you are jumping from questions about container planting to descriptions of issues you have had with plants in the ground. They are very different situations and it is impossible to make meaningful comparisons between the two.

That said, IME (and Al, JAG or others, feel free to jump in with your thoughts) if the potting soil for your containers is well mixed so that all the materials are evenly distributed, there shouldn't be issues with the peat - which is the base for many commercial (and homemade) soil-less potting mixes - drying out as long as you are watering adequately. There shouldn't be any large or hard clumps of peat....it should all be finely and thoroughly incorporated with the other ingredients. Same with peat in the ground. And it is best to moisten it well before using it as an inground soil amendment. And it is not a good idea to amend individual planting holes for inground planting - if you need to amend, do so over a very wide area, like the entire planting bed.

If you are refreshing your container soils each season by adding new soil/potting mix, remove ALL the soil and blend the new stuff into the old thoroughly, then refill. Don't just layer it on top.

Thanks, Josh. I will look for that.

Sorry Gardengal, if what I wrote was confusing. I only see one reference to my beds in the ground in the last part of my second post. I described my terrible experience with poor drainage, and was implying that I understood the need for proper drainage because of that experience. I should have tied the experience with my concern for drainage in the pots.

Would you really dump out all the soil from 4 whiskey barrels, mix the ingredients together, then fill them?

If a person would not consider removing all the soil, but just half, what would be logical ammendments? How would leaving the soil underneath negatively impact the plants if there were plenty of drainage?

(My sphagnum peat moss experience was about 20 years ago.)

I appreciate your response, and your credentials are very impressive.

Sammy

The physical properties of peat moss peat moss as it comes from the bag doesn't change much from year to year. Both peat and pine bark begin to become hydrophobic (water repellent - it has to do with how the Fe atoms on the surface of particles are arranged as the particles dry down) as their moisture content approaches then drops below 30% water content. No matter where you live, the key to preventing this occurrence is to NOT let the soil get that dry - to water more often.

What you can do to help ease this problem when it does occur:
A) Water twice. Supply water to the container and wait a few (10?) minutes so the soil slowly absorbs SOME water, which will break the hydrophobic tendency of the soil. Water a second time & the soil should absorb water much more readily.
B) Incorporate an ingredient that does not become hydrophobic. Turface or vermiculite are examples of material that absorb water readily, even when they seem completely dry. They will absorb water and through diffusion, raise the moisture content of the rest of the soil particles. Even with these ingredients incorporated into the soil, you will probably want to water twice at an interval.

I think though, that the key is to NOT allow your soil to get so dry. I, and many others deal with the heat with no problems. It regularly gets into the 90s and occasionally to 100* here, too - and I don't have a problem on those days; and I can assure you, I grow in a much more open soil (holds less water) than you do. ;o) You should be shading your containers when temperatures are that hot, btw. Root function begins to become seriously impaired as actual root temperatures climb through the 90s.I would discard the soil from the whiskey barrels and start with new. If I HAD to reuse it, I would mix it in my soils at a rate of 5:1:1, fine pine bark:perlite:your old soil. The remainder I would turn into the garden, beds, or compost pile.

Al

Sorry if I repeated advice that others offered. Just take the repetition to mean that the advice that arises from our experience is consistent.

Take care.

Al

I really appreciate everyone's advice. Thank you so much.

I did not know about shading. We have our big barrels in two rows, and are building a fence around them to help keep the plants away from the rabbits and squirrels. We can easily drape or construct something on the side to shade them somewhat.

For the patio plants we are putting a smaller fence around it, and are putting up some rebar arches so we can give protection from a sudden spring freeze.

A really mean it when I say that I appreciate your input. I have been on the rose forums for many many years, and am new here. Just like most of you, I need to adjust my life to make it work for me. I teach school, and in the summer if I am lucky, my children come home to visit. During those visits I often just don't leave them. We do not have an automatic watering system, but my husband has set up emitters at different spots in the garden. It is a chore to care for 200 rose bushes, especially so many climbers and older roses in the back.

If I plan my time wisely, I should be able to grow tomatoes, lettuces, and herbs. My husband wants to grow some eggplants and melon too ---good grief.

My roses are thriving, but keep me very busy. I hope the container plants will also thrive. You have given me some very good suggestions, and I think I will be fine.

Thanks so much.
Sammy

What nice comments, Sammy! I know everyone who posted so far, and I know them well enough to say that your comments won't go unappreciated. ;o)

To be clear, when I mentioned shading, for the most part I meant shading the containers on hot, sunny days to keep soil.root temps down, but on those 95*+ days, it would be nice if you could offer something to keep o/a temperatures down - like moving the smaller containers to shade during the hottest part of the day, or some sort of shade cloth arrangement for the larger plants.

Welcome to the container forum. ;o)

Al

Drainage in containers is still very different from drainage conditions inground, so I'd still not make any comparisons.

And yes, I would dump out all the soil and remix thoroughly. All soil conditions that have any sort of organic component to them change overtime and potting soils are subject to the same eventual breakdown as one would experience in an inground setting and because of their unique conditions, perhaps even faster, which is why Al suggests replacing it entirely. Just adding new mix on top creates unnatural layers or soil strates that will have different textures and these WILL affect drainage negatively (read Al's excellent threads on potting soils and water movements). But being the cheap person I am, I DO reuse potting soil for several seasons before dumping and replacing entirely. And if I mix it well to incorporate it thoroughly with any fresh material, the texture and porosity becomes uniform throughout the mix, maintaining aeration and good drainage.