Heartsy.....sure there is.....throw it away...its of no good use.
I assume we're talking potting mixes/soil....and for what it was used for, it has done its best and is no longer best for your new plantings.

Throw it into the compost....or mix it with some topsoil and throw it where it can fill depressions maybe in your lawn.

For containers, there's nothing better than new, fresh potting soil of good quality.
You can buy inexpensive stuff...you know, the dollar bag...but its usually not very reliable.

Fresh potting soil has in it, all that new, ...and maybe tender, plants need to get off to a good start.
It's a shame to spend money and end up with plants that don't do their best....simply to save a few pennies.

And....as far as using perlite....I am one that avoids this on the principle that it cant hold proper moisture.
VERMICULITE.....that is much better....it gives something to the plant and does hold moisture.

As far as reading about that notion.....there's a very long...and well messaged post here in this journal about the pros and cons of both perlite and vermiculite in container gardening. Not sure just where it is....it was about a month or so ago. But you can read for yourself....just put those two materials in your browser window and compare each of their attributes.

Is there any way that I can safely treat my old soil to make sure there are no bugs, mold or fungus already there.

While I have never done it and can't imagine I ever would as I view it very impractical, you can safely sterilize the potting mix by baking it in the oven. I forget what temperature or how long other than it was quite a low temperature for an oven. I am sure you could google on 'potting soil sterilize' or something similar and find instructions.

I would imagine you could also soak it in a bleach water solution and then rinse really, really, really well.

Again though, seems really impractical.

I would suggest that if you have any concerns about the suitability of your potting mix that you replace it.

If you are reusing a portion because you don't think the plant's require the total volume of soil that the container holds then you can use filler material such as crushed aluminum cans/plastic bottles or whatever recyclable materials you may produce at home.

From one of my '05 replies to the same question. It is a cut/paste job, so keep that in mind if you decide to read it:

In my estimation, the only case to be made for reusing container soils is one of economics, and you'll never find me argue against making that decision. If you can't afford, you can't afford it. That said and setting economics aside, you might decide to reuse soil for reasons other than economical. Perhaps the effort involved with acquiring (or making your own) soil is something you might not wish to go through or be bothered with.
In any case, it would be difficult to show that soils in a more advanced state of structural collapse can somehow be preferred to a soil that can be counted on to maintain its structure for the entire growth cycle. So, if the economic aspect is set aside, at some point you must decide that "my used soil is good enough" and that you're willing to accept whatever the results of that decision are.

All soils are not created equal. The soils I grow in are usually pine bark based & collapse structurally at a much slower rate that peat based soils, yet I usually choose to turn them into the garden or give them over to a compost pile where they serve a better purpose than as a container soil after a year of service. Some plantings (like woody materials and some perennials) do pretty well the second year in the same bark-based soil, and with careful watering, I'm usually able to get them through a third year w/o root issues.

Watering habits are an extremely important part of container gardening. Well structured soils that drain well are much more forgiving and certainly favor success on the part of the more inexperienced gardeners. As soils age, water retention increases and growing becomes increasingly difficult. If your (anyone's) excellence in watering skills allows you to grow in an aging medium, or if your decision that "good enough" is good enough for you, then it's (your decision) is good enough for me, too.

The phrases "it works for me" or "I've done it this way for years w/o problems" is often offered up as good reason to continue the status quo, but there's not much substance there.

I'm being called away now, but I'll leave with something I offered in reply on a recent thread:
"... First, plants really aren't particular about what soil is made of. As long as you're willing to stand over your plant & water every 10 minutes, you can grow most plants perfectly well in a bucket of marbles. Mix a little of the proper fertilizers in the water & you're good to go. The plant has all it needs - water, nutrients, air in the root zone, and something to hold it in place. So, if we can grow in marbles, how can a soil fail?

Our growing skills fail us more often than our soils fail. We often lack the experience or knowledge to recognize the shortcomings of our soils and to adjust for them. The lower our experience/knowledge levels are, the more nearly perfect should be the soils we grow in, but this is a catch 22 situation because hidden in the inexperience is the inability to even recognize differences between good and bad soil(s).

Container soils fail when their structure fails. When we select soils with components that break down quickly or that are so small they find their way into and clog macro-pores, we begin our growing attempts under a handicap. I see anecdotes about reusing soils, even recommendations to do it all over these forums. I don't argue with the practice, but I (very) rarely do it, even when growing flowery annuals, meant only for a single season.

Soils don't break down at an even rate. If you assign a soil a life of two years and imagine that the soil goes from perfect to unusable in that time, it's likely it would be fine for the first year, lose about 25% of its suitability in the first half of the second year, and lose the other 75% in the last half of the second year. This is an approximation & is only meant to illustrate the exponential rate at which soils collapse. Soils that are suitable for only a growing season show a similar rate of decline, but at an accelerated rate. When a used soil is mixed with fresh soil after a growing season, the old soil particles are in or about to begin a period of accelerated decay. I choose to turn them into the garden or they find their way to a compost pile.

Unless the reasons are economical, I find it difficult to imagine why anyone would add garden soils to container soils. It destroys aeration and usually causes soils to retain too much water for too long. Sand (unless approaching the size of BB's), has the same effect. I don't use compost in soils because of the negative effect on aeration/drainage. The small amount of micro-nutrients provided by compost can be more efficiently added, organically or inorganically, via other vehicles.

To boil this all down, a container soil fails when the inverse relationship between aeration/drainage goes awry. When aeration is reduced, soggy soil is the result, and trouble is in the making."

Al

I don't agree in most cases that contaier soil goes bad and is useless after a year.

I mix some fresh soil with old soil every year without any problems. Add some nutrients, whatever.

Many Container soils are more of just a growing medium, closer to hydroponics than dirt. You can grow plants in just peat moss if you wanted to.

You can rejuvinate your old growing medium.

To keep things as on topic as possible I am going to point out that the OP expressed a concern regarding pathogens in the potting mix.

While I don't think reusing potting mixes year after year is the best way to vigorous plants, I know many do it and I have done it myself without serious complications (meaning the plants still grew).

But if disease pathogens in the potting mix are the concern then tossing the mix becomes a no brainer unless one wants to try to sterilize the mix and that seems more trouble than it would be worth.

Heartsy, if you are still going to reuse your own potting medium, and are worried about pathogens, I've attached a link that discussed several methods of sterilization that you can do in your own home. I know of at least one gardenweb forum member (ken, where are you????) that practices this with fervor.

By the way, perlite is absolutely the best amendment you can use to increase the porosity and structure of your old soil. Vermiculite (recommended earlier) turns to mush rapidly.

I've learned over many years that the health and vigor of my container plants is directly correlated with the same for the root system. Thus, I stopped hoarding potting mix from year to year, and begin anew in the spring.

Here is a link that might be useful: Sterilize your soil (beware of the stench)

Al, I remember reading that when you first posted it. Back then I read very intently. Now with the wisdom of a few years (and your information), I read them again as a refresher. Your writings are always a good spring-board.

On the subject of Vermiculite, I agree 100% with Rhizo. I just bare-rooted 80 trees yesterday and today. The cuttings were grown in a 2/3 P:1/3 V mix and the older trees had some Vermiculite in the mix as well. What a mess. In the older trees and even some of the new cuttings the Vermiculte had compressed. Then it sticks to everything. It took me longer by far trying to get that EssAichEyeTea off the roots (and everything else). I'm sure Vermiculite has its place, but its not in my containers. I have already called a friend of mine who ships liquid filled containers and offered him the Vermiculite I have left.

BTW... I don't reuse either. All the mix I stripped off the roots filled a few low spots in the yard. ;) However, that may change in the future since the only component of my mix that will degrade is the pine bark. I figured I can screen what comes out of the pot, add a like amount of pine bark as what is under the screen and have something very close to day one.

~james

You're very kind, James.

I just disagreed with someone over the use of vermiculite in soils and the wording in the post was similar to Jeannie's (above), so I figured it was hers & it would be redundant to disagree again, but I'm with you & Dorie on this one - I use it rarely & then in only highly individualized soils. I still remember something Dorie said about the difference between perlite and vermiculite: "Vermiculite and perlite are very different. Physically, vermiculite collapses in about, oh, ten minutes....." I thought it was quite funny. ;o)

If I had to choose a relatively lightweight inorganic component for soils aside from things like perlite, Turface, Haydite, pumice, etc., I would consider granular rockwool long before considering vermiculite.

Your screening idea does kind of reset the soil-life timer for the type of soils you are using, and I admire your ambition (screening it), James.

I read your posts frequently & notice that your diligence has brought you a long way over the last few years. Strong work! ;o)

Al

Sorry for the derail, but there is just something I have to understand about perlite.

The stuff crumbles readily between my fingers with little pressure. At first I thought it was because of the freeze/thaw cycle with outdoor containers, but then I noticed that the perlite in my houseplant containers also crumbled readily.

In both cases the potting mix is only around 6-8 months old.

I have asked Rhizo about this in a different thread and she indicated this didn't happen for her, but I read a couple posts on another forum where people were saying perlite also crumbled readily in short order for them.

So, what's the deal here?

I hate perlite for many reasons, but is there more than one perlite (apart from size)? I realize the question sounds silly, but how can it be some people observe the stuff readily crumbles in short order and others observe that it doesn't?

It crushes readily between my fingers too, but I try not to do that to the stuff I use in soils. ;o)

I've never noticed any appreciable breakdown in particulate size. I have a few plants that have been in 100% perlite for two-three years & the pieces on the top are the same size as they were when the cuttings were potted. I usually use large size hort grade & medium when I can't get large, but the brand usually varies while properties seem to remain consistent. I've often left containers exposed to freeze thaw cycles all winter before turning the soil into the garden or compost pile & never observed a deterioration in particulate size from freezing either.

Not sure why you hate it ..... but to each his own. I find it invaluable in the soils I use for planting things short term & the "pretty stuff" type of display containers, as well as those used for veggies.

Al

New or old? I do both.

If I have paid $5 for a pack of 10 seeds, there is no way I'm going to develope those plants in an old soil mix certain to have common pathogens.

On the other hand, if I'm growing plants with low vulnerability to common pathogens, it's cheaper to use a modified garden soil. An example would be 20 mums set to 2 gal pots. Using a sterile mix would bust my budget.

I have some containers where the same soil has been in place for over 10 years. There are no organics in this mix, so it does not degrade or change from year to year. It's basicly a mix of clay, sand, and some decomposed vermiculite.

I suppose we should be happy that the mix you describe ("basicly a mix of clay, sand, and some decomposed vermiculite") works for you, but I'd also caution others that it won't likely work for them.

Al

Very true Al. I should have said the same. Not many garden soils, even with amendment, are successful container soils.

One must always observe the physical properties of soil that were so well noted by Al in his post on water movement in containers (Container soils and water in containers). Using clay in containers starts there and goes a bit further.

Heartsy, I have poured boiling water through smaller amounts( 1-2 gallons)of used soil to kill bugs and eggs. It's less smelly than baking it. Just let it drain well and dry out a bit before mixing it with your new soil.
And don't everyone yell at me, sometimes you have to use what you have on hand! :D

There is absolutely no way to attack the idea of using OLD....when someone says "well, I've been using the same old soil for ten years and got results".

That said....I usually answer that by suggesting...
"OK, you have had good results....but if you had used NEW then you would have attained twice as good results.
And using garden soil where potting soil is THE only one to use....that idea just makes me shudder.

(not having any way of course of proving that relationship...I say it anyway)

And as far as seeds are concerned, retaining moisture is a vital part of bringing the seed along.
Perlite....does not hold moisture....vermiculite does.
And as far as I'm concerned, perlight/vermiculite do just about the same thing.....but verm holds moisture.

Seed starting I like using vermiculite and peat moss --about 50-50.

jeannie7 said ...but if you had used NEW then you would have attained twice as good results.

In May I took mum cuttings, rooted in a sand bed. In June they were set to 6" containers using garden soil from a bed. In August they were planted back to the same bed the container soil came from. I wonder what they would have looked like if the results had been twice as good.

September mums ....

{{gwi:5544}}

There is no right or wrong answer, experiment for yourself and do what works best in your hands and with your plants

Personally, I think perlite is great, I have not seen it break down even after 10+ years, what I don't like is how it floats to the top.

Vermiculite is useful short term for things like starting seedlings, as it retains moisture and aerates nicely until it transforms back into the clay components that it originated from.

Garden soil, if low in organic components, mixed with drainage or aerating components like perlite, turface, etc, can be stable for many years, as long as it is supplemented with nutrients and trace elements. This is a stable but heavy (dense) mix, and is useful for plants that don't grow so fast, like succulents.

When you start using things like peat, compost or bark, all of which decompose at different rates, you need to carefully consider what you are growing and your skills, and adjust or repot as needed. These components generally "lighten" the soil (or soil-less) mix

There are so many variables. Quick growing plants, like some tropical species, some trees, etc, probably do best in lighter mixes with periodic repotting.

My advice: try out everything on your own, experiment with cheap plants and see what kinds of results you get, then, and only then, will you really understand.

x

I have used older and tired out soil mixed with amendments at times and have had great results. As long as your soil is not diseased and mucky, no problem; although I agree it is best to start with new soil (as in containers) each year. Amending your soil in the garden is important as the plants take their energy from it a lot, as well as from the photosynthesis involving the sun. A good foundation is best; the old saying is "feed the soil, not the plants"! But it is not always a matter of dire consequence. You can sometimes get by for another season with the old.

I'm not sure how the notion that perlite has no water retention ability got started, but it's incorrect. Because of its rather unique structure, perlite is well able to retain water, absorbing 3-4 times its weight, depending on grade. This compares to 3-5 times the weight for vermiculite - all in all, pretty comparable. The advantage is that perlite is able to maintain its structure and porosity indefinitely, whereas vermiculite will breakdown in time, typically within a single growing season, compress and lose both its porosity and its water holding abilities.

I do reuse container soils but refresh them with additions of new materials at approximately 50%. I have not found that reuse to this extent has had any negative effect on the plantings or their vigor. As to the need to sterilze used container soils or the containers themselves, if you have not experienced disease issues with the soils or the pots previously, then this may be an unnecessary process. Personally, the home sterilization of potting soil is not something I care to engage in (stench is a very apt description of the side effects!). If I suspect a disease issue with any container medium, it gets dumped in the compost for the soil organisms to digest and combat.

Perhaps the confusion stems from whether Perlite adsorbs ro absorbs water. From an article on the Schundler website:

"Since finer grades of perlite have far more surface area and will hold far more water, it is logical that the highest wet bulk densities occurred with fine grades of perlite and the lowest wet bulk densities occurred with coarse grades."

and another article:

"...because of its unique surface configuration, particles of horticultural perlite will retain from three to four times their weight in water on the surface yet they will not become soggy."

~james

Here is a link that might be useful: PERLITE GRADATION AND PEAT/PERLITE MIXTURES

Because of its rather unique structure, perlite is well able to retain water, absorbing 3-4 times its weight, depending on grade. This compares to 3-5 times the weight for vermiculite - all in all, pretty comparable.

How much water something can hold in relation to it's weight isn't all that meaningful in terms of gardening in containers of limited volume.

Water is heavy, perlite is not.

Doesn't it make more sense to express a substance's water holding ability in terms of volume rather than weight?