One of the problems associated with reusing your soilless potting medium over and over again is that very few of the commercially available mixes hold up over time. As they begin to break down, that all important porosity begins to collapse, as the particle sizes of the solids diminish. If, however, you have a very coarse mix, or one that you have added a great deal of coarse amendments to, then you can easily get a few seasons out of it. Remember, in containers, the pore spaces (which hold the crucial air supply for the roots, as well as facilitate speedy drainage of excess water) are critical for the health and vigor of plants.

I know that many people will jump in and proclaim that they use the same potting soil over and over again and OVER again. Maybe so, but you aren't doing your plants (or you) any favors unless the soil texture remains coarse.

That being said, potting mixes can be baked in the oven, or stream treated via solarization techniques. Even composting, if hot enough, can rid a soil of some critters and pathogens. Sufficient heat is the required factor in removing the 'cooties'.

I think over years on GW, many of the ones who have reported reusing like myself, have noted that they mix some of the old mix (in my case, ~1/3rd) with fresh mix (~2/3), then add that back to the container and plant. This is for containers of single season plants because I am surely not repotting all my shrubs and perennials every year (the exceptions being fast-growing perennials that may need to be divided like daylilies, irises, etc). The other 2/3rds of old mix can subsequently be mixed with fresh soil in a similar fashion for additional containers.

THAT sounds like a great idea! Kmekaru, if you are still there...have you tried to ID the problem with your strawberries?

Thanks for all the info!!! This mesage board is great! Once I cut down all of my tomato and plants, I will bake the soil in the oven and probably use some to compost. I will also purchase a bag of new soil and mix as suggested for next season.

As for my strawberry plants, the problem is that the older leaves are always dying off. They slowly brown and then completely brown. This didn't happen to one of my other strawberry plants, so I was assuming it's verticulum wilt...I really want to make sure I start fresh with no diseases in the soil, so I'll take precaution next growing season. Thanks for all the advice!

Just a word of caution - if "baking" your soil, keep the windows and doors open and the oven fan on full force. Cooking soil has a very distinctive aroma that is NOT similar to other, more edible baked goods :-)

While not unheard of, verticillium wilt in container plantings is rare, generally because the source of the disease is not present in the potting medium. It could be introduced by contaminated amendments or by infected stock. You might want to try replanting your berries with VW resistant cultivars.

I dont see what is wrong with useing the same soil over and over. Look at our wild areas and you will see soil growing beautiful forest useing the same soil over and over. Stop contaminating your potting soil with man made junk and chemicals that are not a part of nature, and you can use the soil over many times. I may not have the over saze plants and highly productive plants but I dont have to spend a fortune on soil and chemicals. I make my potting soil useing natural things composted and use natural fert.

One thing that no one has mentioned in this converstation is the second reason why I don't re-use my potting medium. I CAN'T reuse it! At the end of a growing season, I can't separate the roots from the growing medium if I try! Makes good compost, though. ;-)

I've reused my potting soil now for 2 growing seasons. Like someone else here mentioned,

I didn't go 100% reused for a "fresh" mix, but added 25% fresh peat and some new perlite.

Now for what I do....

The first thing I do is let whatever plant is in the pot die off completely. This seems

to remove a good portion of the live root system as well as much of the green foliage.

Once that's done, I shake out as much of the soil as I can into a 5 gallon bucket that I

keep on the side of the house. Any large clumps of roots I take out and toss in the

garden, in the beds around the house, etc. I keep that bucket going until it's full.

When that bucket is full, I take that soil out and transfer it to large lasagna sized

aluminum baking trays that I picked up at the local dollar store. Just to the edge of the

top, not overfull or they take forever. I typically get 4 of these trays per 5 gallon

bucket. I take those, 2 at a time, and bake them at 325 for 2-3 hours in the over. It

does smell like earth cooking here, but I actually like the smell. It's the pieces that

fall off the tray into the oven and come back smelling later, that can be nasty

(especially when it actually *is* lasagna in the oven).

When it's all baked off I dump the trays into a wheel-barrow that I keep by the house and

let it cool. Once cool, I add 1 small bag of peat to 5 gallons of reused soil. I then add

some perlite, perhaps 1/2 a bag to break up the mix a bit.

The first thing I've noticed, the longer the reused mix sits in the 5 gallon bucket, the

"cleaner" it is at this point. I've settled in on around 4 weeks in the bucket before I

bake it.

Next, the Ph is almost always off, tends to be on the low side and needs lime to bring it

up. Mine typically registers around the 5.7 to 6.0 on my testers so I add lime to bring

it up to ~6.8. If you're planning on rolling your own soil, regardless of the sources,

test the Ph before you use it.

I also add 1/2 cup of slow release granules to the wheel-barrow mix (Osmocote) and have

also ammended with bone meal and blood meal for higher fast acting N & P soils. One thing

I have found is that reused soils the way I've made is low in calcium and magnesium so I

augment with a good fish/kelp emulsion (or even a mix).

Use organic fertilizers, fish and kelps are by far the best I have used. The brand I use

is Neptune's Harvest but I've heard that Earthjuice is really good as well. Get away from

chemicals, they're not necessary and plants have a difficult time processing them.

To give an idea on reuse numbers here. I just finished baking the rest of the containers

I had from the summer and have ~90 gallons of fresh potting soil. For what cost me around

$40 in peat and perlite (forget my time) I have perhaps $500 in potting soil at my

disposal. Go to Walmart and pick up the $7.99 17 gallon plastic tubs, they're perfect for

winter storage of what you've made. I really believe more people should reuse what they

have instead of tossing it out. If you do toss it, by all means, please do so

Thanks for all the info!!! This mesage board is great! Once I cut down all of my tomato and plants, I will bake the soil in the oven and probably use some to compost. I will also purchase a bag of new soil and mix as suggested for next season.

There is a way to reuse potting mix for many years and not have to worry about the particle size becoming smaller.

It is fairly easy and inexpensive as well.

The reason that old potting mixes become undesirable is due to 2 primary factors. Disease and drainage/aeration.

Any time a container plant gets diseased one needs to either understand precisely what the disease is and whether it can overwinter in the mix and what it can affect and then plant accordingly, *or* more simply, toss it.

Ignoring disease issues, the other reason to replace planting mix is the reduction in particle size. This reduces drainage because the particles are more tightly compressed and capillary action is stronger between the particles. Space for oxygen is also reduced and this is the major problem. Oxygen is the most overlooked key to gardening success. Lots of talk is made about loose, light growing mediums, but the *reason* these are good is they support higher oxygen levels for the roots.

So, what is the way to not worry about the potting mix?

Aeration tubes.

A simple piece of PVC pipe with lots of holes drilled into it inserted into the mix works.

The tube can be place vertically in the pot and mix filled around it or (better) one can drill a hole through both sides of a pot and the tube inserted with landscape fabric wrapped around it (to keep mix out).

This effectively aerates the container in the same way it does compost piles.

Yup, it's a small amount of work up front, but it reduces the expense and labor or replacing or 'refreshing' planting mixes each year.

Earth boxes, which are commercial, self watering containers make use of this technique (vertical tube also used for adding water))to get sufficient oxygen into what is otherwise a 'closed system'.

It works.

I think running it through a hot compost heap and then mixing in organic fertilizer before you plant in it again, is the way to go.
-O

youngd24, could you please email me, directly to bluelytes at yahoo dot com, thanx.

His post is nearly 2 years old, so don't be too surprised if you don't get a response.

Al

Hi there all you who bake your soil, please show me where mother nature bakes her soil then look out there in the wild areas that man has not messed up and see what NOT baking does to the soil, just a thought. DAN

dangsr, while I think I understand your point, keep in mind we are talking about container soil, which as we all know is quite a different beast from garden soil. Mother Nature doesn't often tend to intentionally plant in man-made containers :-) Cultivated gardening and container gardening in particular tend to create situations that cannot be effectively resolved by just adhering to processes/practices observed in the natural, uncultivated environment.

I had this almost finished, but got called away. I see my dear friend Pam has already been here.

Mother Nature doesn't confine her plants to containers, so she has made little provision for their culture when WE do. One of the things that sets man apart from other animals is his wonderful ability to adapt to most of the myriad adversities found in his environment. Though I've never considered baking a soil for any reason, those that do are simply figuring out how to adapt to what comes their way. Right, wrong, or immaterial, I prefer to view it as testimony to a greater degree of dedication to their growing experience than most of us exhibit.

Just as popcorn is a natural product made better by applying heat, perlite, vermiculite, and Turface are, too. Crushed granite makes up, up to 95% of many mineral soils, (just a little finer) so where is the beef that prompts you to offer "Stop contaminating your potting soil with man made junk and chemicals that are not a part of nature, and you can use the soil over many times. I may not have the over saze plants and highly productive plants but I dont have to spend a fortune on soil and chemicals." (Some of us are very results-oriented and don't find this acceptable.) Is the real issue here a dislike of chemical fertilizers?

"I make my potting soil useing natural things composted and use natural fert."

99% of everyone reading this reply uses all natural materials in their container soils, so we're little different from you in that regard. I find it pretty difficult to imagine how changing the list of natural ingredients would exempt anyone from things like disease/insect carry-over and soil collapse.

Al